Sorption of four hydrophobic organic contaminants by biochars derived from maize straw, wood dust and swine manure at different pyrolytic temperatures

Synergistic interactions and reaction mechanisms of biochar surface functionalities in antibiotics removal from industrial wastewater

Biochar, a carbon-rich material with a unique surface chemistry (high abundance of surface functional groups, large surface area, and well-distributed), has shown great potential as a sustainable solution for industrial wastewater treatment as compared to conventional industrial wastewater treatment techniques demand substantial energy consumption and generate detrimental byproducts. This critical review emphasizes the surface functionalities formation and development in biochar to enhance its physiochemical properties, for utilization in antibiotics removal. Factors affecting the formation of functionalities, including carbonization processes, feedstock materials, operating parameters, and the influence of pre-post treatments, are thoroughly highlighted to understand the crucial role of factors influencing biochar properties for optimal antibiotics removal. Furthermore, the research explores the removal mechanisms and interactions of biochar-based surface functionalities, hydrogen bonding, encompassing electrostatic interactions, hydrophobic interactions, π-π interactions, and electron donor and acceptor interactions, to provide insights into the adsorption/removal behavior of antibiotics on biochar surfaces. The review also explains the mechanism of factors influencing the removal of antibiotics in industrial wastewater treatment, including particle size and pore structure, nature and types of surface functional groups, pH and surface charge, temperature, surface modification strategies, hydrophobicity/hydrophilicity, biochar dose, pollutant concentration, contact time, and the presence of coexisting ions and other substances. Finally, the study offers reusability and regeneration, challenges and future perspectives on the development of biochar-based adsorbents and their applications in addressing antibiotics. It concludes by summarizing the key findings and emphasizing the significance of biochar as a sustainable and effective solution for mitigating antibiotics contamination in industrial wastewater.

An effective strategy for biodegradation of high concentration phenol in soil via biochar-immobilized Rhodococcus pyridinivorans B403

High concentration of phenol residues in soil are harmful to human health and ecological safety. However, limited information is available on the in-situ bioremediation of phenol-contaminated soil using biochar as a carrier for bacteria. In this study, bamboo -derived biochar was screened as a carrier to assemble microorganism-immobilized composite with Rhodococcus pyridinivorans B403. Then, SEM used to observe the micromorphology of composite and its bioactivity was detected in solution and soil. Finally, we investigated the effects of free B403 and biochar-immobilized B403 (BCJ) on phenol biodegradation in two types of soils and different initial phenol concentrations. Findings showed that bacterial cells were intensively distributed in/onto the carriers, showing high survival. Immobilisation increased the phenol degradation rate of strain B403 by 1.45 times (37.7 mg/(L·h)). The phenol removed by BCJ in soil was 81% higher than free B403 on the first day. Moreover, the removal of BCJ remained above 51% even at phenol concentration of 1,500 mg/kg, while it was only 15% for free B403. Compared with the other treatment groups, BCJ showed the best phenol removal effect in both tested soils. Our results indicate that the biochar-B403 composite has great potential in the remediation of high phenol-contaminated soil.

Mechanisms of female reproductive toxicity in pigs induced by exposure to environmental pollutants

Environmental pollutants, including endocrine disruptors, heavy metals, nanomaterials, and pesticides, have been detected in various ecosystems and are of growing global concern. The potential for toxicity to non-target organisms has consistently been raised and is being studied using various animal models. In this review, we focus on pesticides frequently detected in the environment and investigate their potential exposure to livestock. Owing to the reproductive similarities between humans and pigs, various in vitro porcine models, such as porcine oocytes, trophectoderm cells, and luminal epithelial cells, are used to verify reproductive toxicity. These cell lines are being used to study the toxic mechanisms induced by various environmental toxicants, including organophosphate insecticides, pyrethroid insecticides, dinitroaniline herbicides, and diphenyl ether herbicides, which persist in the environment and threaten livestock health. Collectively, these results indicate that these pesticides can induce female reproductive toxicity in pigs and suggest the possibility of adverse effects on other livestock species. These results also indicate possible reproductive toxicity in humans, which requires further investigation.

Biochar-based materials as remediation strategy in petroleum hydrocarbon-contaminated soil and water: Performances, mechanisms, and environmental impact

Petroleum contamination is considered as a major risk to the health of humans and environment. Biochars as low-cost and eco-friendly carbon materials, have been widely used for the removal of petroleum hydrocarbon in the environment. The purpose of this paper is to review the performance, mechanisms, and potential environmental toxicity of biochar, modified biochar and its integration use with other materials in petroleum contaminated soil and water. Specifically, the use of biochar in oil-contaminated water and soil as well as the factors that could influence the removal ability of biochar were systematically evaluated. In addition, the modification and integrated use of biochar for improving the removal efficiency were summarized from the aspects of sorption, biodegradation, chemical degradation, and reusability. Moreover, the functional impacts and associated ecotoxicity of pristine and modified biochars in various environments were demonstrated. Finally, some shortcoming of current approaches, and future research needs were provided for the future direction and challenges of modified biochar research. Overall, this paper gain insight into biochar application in petroleum remediation from the perspectives of performance enhancement and environmental sustainability.

Carbon-based adsorbents for the mitigation of polycyclic aromatic hydrocarbon: a review of recent research

Accumulation of polycyclic aromatic hydrocarbons (PAH) poses significant dangers to the environment and human health. The advancement of technology for cleaning up PAH-contaminated environments is receiving more attention. Adsorption is the preferred and most favorable approach for cleaning up sediments polluted with PAH. Due to their affordability and environmental friendliness, carbonaceous adsorbents (CAs) have been regarded as promising for adsorbing PAH. However, adsorbent qualities, environmental features, and factors may all significantly impact how well CAs remove PAH. According to growing data, CAs, most of which come from laboratory tests, may be utilized to decontaminate PAH in aquatic setups. However, their full potential has not yet been established, especially concerning field applications. This review aims to concisely summarize recent developments in CA, PAH stabilization processes, and essential field application-controlling variables. This review analysis emphasizes activated carbon, biochar, Graphene, carbon nanotubes, and carbon-nanomaterials composite since these CAs are most often utilized as adsorbents for PAH in aquatic systems.

Characteristics of dissolved organic matter composition in biochar: Effects of feedstocks and pyrolysis temperatures

Biochar has widely used in soil pollution remediation due to its advantages of high efficiency and environmental sustainability. Dissolved organic matter (DOM) released by biochar plays a non-negligible role in the migration and transformation of pollutants in environment, and its composition was regarded as main impact factor. In this study, 28 biochar were investigated to detect the effect of pyrolysis temperature and feedstock on DOM content and components. Results showed that the content of DOM released from biochar at low pyrolysis temperatures (300-400 ℃) was higher than that from high pyrolysis temperatures (500-600 ℃). In addition, the specific UV-Visible absorbance at 254 nm (SUVA254) results expressed that DOM from peanut shell biochar (PSBC), rice husk biochar (RHBC) and bamboo biochar (BBC) had higher humification at high temperatures. Moreover, one fulvic acid-like (C2) and two humic acid-like (C1, C3) substances were main fluorescent components of biochar-derived DOM identified by parallel factor analysis based on excitation emission matrices fluorescence spectroscopies (EEM-PARAFAC). With the increase of pyrolysis temperature, humic acid substances content gradually decreased. The correlation analysis results revealed that pyrolysis temperatures and O/C, H/C, DOM content, the biological index (BIX), humification index (HIX), C1% and C3% was negatively correlated (p < 0.001). Thus, the pyrolysis temperatures take important roles in composition of DOM released from biochar, and this research would provide a reference for the application of biochar in the environment.

Adsorption and desorption of polychlorinated biphenyls on biochar colloids with different pyrolysis temperatures: the effect of solution chemistry

Biochar releases colloidal particles into the environment during applications and aging which can become carriers of pollutants and influence on the environmental risk of pollutants due to the excellent adsorption and migration properties of biochar colloids (BCCs). The adsorption and desorption behaviors of BCCs can be different from their bulk ones due to the colloidal size, which merits specific studies. Herein, the adsorption and desorption of 2,4,4'-trichlorobiphenyl (PCB28) as a representative on BCCs released from bulk biochars prepared from bamboo chips at 300, 500, and 700 C and the effects of solution properties were specifically investigated. Results show that the adsorption was dominated by pore filling and π-π interaction, and thus, BCCs prepared at higher temperature with greater pore volume and aromaticity had higher adsorption of PCB28. Results show that the adsorption was dominated by pore filling and π-π interaction, and thus, BCCs prepared at higher temperature with greater pore volume and aromaticity had higher adsorption of PCB28. The saturation adsorption amounts of PCB28 on BCC300, BCC500, and BCC700 were 21.9, 40.3, and 62.4 mg/g, respectively. It is noteworthy that PCB28 possessed a significant desorption hysteresis from BCCs, with the hysteresis index (Ce = 80 μg/L) increased from 0.380 to 0.661 as the preparation temperature of BCCs rising from 300 to 700 ℃. High concentration of NaCl (100 mmol/L) was unfavorable for the adsorption and desorption. The presence of humic acid or fulvic acid (FA), especially the smaller FA, could inhibit the adsorption and desorption of PCB28 on BCCs due to micropore blocking. In seawater, groundwater, surface water, and soil solution samples, the PCB28 adsorption of BCCs was inhibited to varying degrees in comparison with that in deionized water, and the desorption was noticeably inhibited in the groundwater sample. These findings provide valuable information for the understanding of interactions between BCCs and organic contaminants in natural waters and for the environmental application of biochars as well.

Sewage sludge biochars as effective PFAS-sorbents

The use of sewage sludge to produce biochar-based sorbents for per- and polyfluoroalkyl substances (PFAS) removal from water and soil may be an economically and environmentally sustainable waste management option. This study compared the sorption of six perfluorinated carboxylic acids (PFCAs) by two sewage sludge biochars (SSBCs) and one wood chip biochar (WCBC), dry pyrolyzed at 700 °C. Batch sorption tests were conducted by adding individual PFCAs and a PFCA-mixture to pure biochars and mixtures of biochar and a sandy soil (1.3% TOC). PFAS-sorption to the SSBCs exhibited log-linear biochar-water distribution coefficients (log K_d), comparable to those previously reported for commercial activated carbons (e.g., 5.73 ± 0.02 for perfluorooctanoic acid at 1 µg/L). The strong sorption of PFCAs was attributed to the SSBCs relatively high pore volumes in the pore size range that can accommodate these compounds. Sorption was attenuated by the presence of soil (by factors 3-10), by the presence of a mixture of PFCAs (by factors of 6-532) and by both together (by factors of 8-6581), indicating strongly competitive sorption between PFCA-congeners, and less severe sorption attenuation by soil organic matter. These findings could enable sustainable value chains for SSBs in soil remediation and water filtration solutions.

Potential of Biochar from Wood Gasification to Retain Endocrine Disrupting Chemicals

In this study, a biochar obtained from poplar wood gasification at a temperature of 850 °C was used to adsorb the xenoestrogens 4-tert-octylphenol (OP) and bisphenol A (BPA) and the herbicide metribuzin from water. Scanning electron microscopy (SEM-EDX) and Fourier-transform infrared (FTIR) spectroscopy were employed to investigate the surface micromorphology and functional groups composition of biochar, respectively. The study of sorption kinetics showed that all compounds achieved the steady state in less than 2 h, according to a pseudo-second order model, which denoted the formation of strong bonds (chemisorption) between biochar and the compounds. Adsorption isotherms data were described by the Henry, Freundlich, Langmuir and Temkin equations. At temperatures of 10 and 30 °C, the equilibrium data of the compounds were generally better described by the Freundlich model, although, in some cases, high correlation coefficients (r ≥ 0.98) were obtained for more than one model. Freundlich constants, K_F, for OP, BPA and metribuzin were, respectively, 218, 138 and 4 L g^-1 at 10 °C and 295, 243 and 225 L g^-1 at 30 °C, indicating a general increase of adsorption at higher temperature. Desorption of all compounds, especially OP and BPA, from biochar was slow and very scarce, denoting an irreversible and hysteretic process. Comparing the results of this study with those reported in the literature, we can conclude that the present biochar has a surprising ability to retain organic compounds almost permanently, thus behaving as an excellent low-cost biosorbent.

Effect of carrier gas during pyrolysis on the persistence and bioavailability of polycyclic aromatic hydrocarbons in biochar-amended soil

In this study the persistence (based on extractable, C_tot) and bioavailability (based on freely dissolved content, C_free) of polycyclic aromatic hydrocarbons (PAHs) in biochar-amended soil was investigated. Biochar produced at 500 or 700 °C from sewage sludge (BC) or sewage sludge and willow (W) mixture (BCW) in an atmosphere of nitrogen (N₂) or carbon dioxide (CO₂) was evaluated. The biochars were applied to the real soil (podzolic loamy sand) at a dose of 2% (w/w). The content of C_tot and C_free PAHs was monitored for 180 days. The biochar production conditions determined the C_tot and C_free PAHs in the soil. A change of carrier gas from N₂ to CO₂ caused an increase in C_tot PAH losses in the soil from 19 to 75% for the biochar produced from SL and from 49 to 206% for the co-pyrolyzed biochar. As regards C_free PAHs, the change from N₂ to CO₂ increased the losses of C_free PAHs only for the biochar derived from SL at a temperature of 500 °C (by 21%). In the soil with the other biochars (produced at 700 °C from SL as well as at 500 and 700 °C from SL/W), the C_free increased from 17 to 26% compared to the same biochars produced in an atmosphere of N₂.

Considerations for evaluating innovative stormwater treatment media for removal of dissolved contaminants of concern with focus on biochar

Stormwater from complex land uses is an important contributor of contaminants of concern (COCs) such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), Copper, and Zinc to receiving water bodies. A large portion of these COCs bind to particulate matter in stormwater, which can be removed through filtration by traditional media. However, the remaining dissolved COCs can be significant and require special attention such as engineered treatment measures and media. Biochar is a porous sorbent produced from a variety of organic materials. In the last decade biochar has been gaining attention as a stormwater treatment medium due to low cost compared to activated carbon. However, biochar is not a uniform product and selection of an appropriate biochar for the removal of specific contaminants can be a complex process. Biochars are synthesized from various feedstocks and using different manufacturing approaches, including pyrolysis temperature, impact the biochar properties thus affecting ability to remove stormwater contaminants. The local availability of specific biochar products is another important consideration. An evaluation of proposed stormwater control measure (SCM) media needs to consider the dynamic conditions associated with stormwater and its management, but the passive requirements of the SCM. The media should be able to mitigate flood risks, remove targeted COCs under high flow SCM conditions, and address practical considerations like cost, sourcing, and construction and maintenance. This paper outlines a process for selecting promising candidates for SCM media and evaluating their performance through laboratory tests and field deployment with special attention to unique stormwater considerations.

Review on carbon-based adsorbents from organic feedstocks for removal of organic contaminants from oil and gas industry process water: Production, adsorption performance and research gaps

Large amounts of process water with considerable concentrations of recalcitrant organic contaminants, such as polycyclic aromatic hydrocarbon (PAHs), phenolic compounds (PCs), and benzene, toluene, ethylbenzene, and xylene (BTEX), are generated by several segments of oil and gas industries. These segments include refineries, hydraulic fracturing (HF), and produced waters from the extraction of shale gas (SGPW), coalbed methane (CBMPW) and oil sands (OSPW). In fact, the concentration of PCs and PAHs in process water from refinery can reach 855 and 742 mg L^-1, respectively. SGPW can contain BTEX at concentrations as high as 778 mg L^-1. Adsorption can effectively target those organic compounds for the remediation of the process water by applying carbon-based adsorbents generated from organic feedstocks. Such organic feedstocks usually come from organic waste materials that would otherwise be conventionally disposed of. The objective of this review paper is to cover the scientific progress in the studies of carbon-based adsorbents from organic feedstocks that were successfully applied for the removal of organic contaminants PAHs, PCs, and BTEX. The contributions of this review paper include the important aspects of (i) production and characterization of carbon-based adsorbents to enhance the efficiency of organic contaminant adsorption, (ii) adsorption properties and mechanisms associated with the engineered adsorbent and expected for certain pollutants, and (iii) research gaps in the field, which could be a guidance for future studies. In terms of production and characterization of materials, standalone pyrolysis or hybrid procedures (pyrolysis associated with chemical activation methods) are the most applied techniques, yielding high surface area and other surface properties that are crucial to the adsorption of organic contaminants. The adsorption of organic compounds on carbonaceous materials performed well at wide range of pH and temperatures and this is desirable considering the pH of process waters. The mechanisms are frequently pore filling, hydrogen bonding, π-π, hydrophobic and electrostatic interactions, and same precursor material can present more than one adsorption mechanism, which can be beneficial to target more than one organic contaminant. Research gaps include the evaluation of engineered adsorbents in terms of competitive adsorption, application of adsorbents in oil and gas industry process water, adsorbent regeneration and reuse studies, and pilot or full-scale applications.

Microwave biochars produced with activated carbon catalyst: Characterization and sorption of volatile organic compounds (VOCs)

A series of microwave biochars derived from wheat straw in the presence of a granulated activated carbon (GAC) catalyst, using a range of microwave conditions, were produced, characterized and tested as sorbents of three benzene series volatile organic compounds (VOCs). The microwave biochar with the greatest specific surface area (SSA), total pore volume (TPV), and micropore volume (312.62 m² g^-1, 0.2218 cm³ g^-1, and 0.1380 cm³ g^-1, respectively), were produced with 1:3 biomass:GAC catalyst mass ratio, 10 min microwave irradiation time, and at 500 W power level (WB500). Maximum adsorption capacities of WB500 to benzene, toluene and o-xylene were 53.9 mg g^-1, 75.8 mg g^-1 and 63.0 mg g^-1, respectively, and were directly correlated to microwave biochar properties such as SSA, TPV or micropore volume, but were also influenced by VOC properties such as molecular polarity and boiling point. Kinetic modeling suggested that adsorption was governed by both physical partitioning and chemisorption mechanisms. In addition, microwave biochars maintained 79% to 92% of their initial adsorption capacity after ten adsorption/desorption cycles. These results suggest that microwave biochars produced with an GAC catalyst have excellent potential for efficient use in the removal of VOCs from waste gas.

Effects of slag and biochar amendments on microorganisms and fractions of soil organic carbon during flooding in a paddy field after two years in southeastern China

Incorporating amendments of industrial waste such as biochar and steel slag in cropland has been used to enhance the storage of soil organic carbon (SOC) while sustaining crop production. Short-term laboratory and field studies have identified important influences of biochar on active SOC fractions associated with soil microbial activity in paddy soils, but the long-term effects remain poorly understood. To address these knowledge gaps, we examined the effects of slag, biochar, and slag+biochar treatments on total SOC concentration, active SOC fractions and soil microbial communities in a paddy field two years after incorporation. Across both two seasons, the addition of slag, biochar, slag+biochar increased soil salinity by 26-80%, 1.3-37% and 42-79%, and also increased soil pH by 0.8-5.7%, 2.1-2.4% and 4.0-6.3%, respectively, relative to the control. SOC concentration was higher in the slag, biochar, and slag+biochar treatments across both rice seasons by 4.3-5%, 0.5-17% and 4.3-7%, respectively. Soil C-pool activity and C-pool management indices in the late paddy season were significantly lower in the slag+biochar treatment than the control by 26.3 and 21.3%, respectively, indicating that the amendments contributed to the stability of SOC. The C concentrations of the biochar and slag amendments affected bacterial abundance more than fungal abundance and affected C cycling. Our study suggests that combined slag and biochar amendments may increase bacterial abundance that may maintain SOC storage and reduce the abundances of potential SOC decomposers in key functional genera, indicating strong coupling relationships with changes of soil properties such as salinity, pH, and SOC concentration. These outcomes due to the amendments (e.g. slag+biochar) may increase microbial C-use efficiency and support the stability of active SOC fractions, with opportunities for long-term C sequestration.

Agricultural waste-derived biochars from co-hydrothermal gasification of rice husk and chicken manure and their adsorption performance for dimethoate

This study aimed to combine energy utilisation of agricultural wastes with the dimethoate (DT) adsorption from agricultural wastewater via hydrogen and biochar production using co-hydrothermal gasification (CHTG). The gasification behaviour after CHTG of five ratios of rice husk (RH) and chicken manure (CM) and the corresponding adsorption performance of biochars on DT were evaluated. The results demonstrated that the feedstock of 3RH+ 1CM achieved the maximum gas yield and hydrogen gasification efficiency (HGE), and the highest adsorption capacity of the derived biochars was 3.57 mg g^-1. Surface characterisation and elemental analysis showed that the biochar derived under different C/N ratios varied considerably. The results of the isotherm and kinetic simulation showed that the Langmuir model and pseudo-first-order model best fitted the experimental data. The superior performance of agricultural waste-derived biochars (AWB) over five cycles of regeneration and adsorption indicated that AWB is a green and stable adsorption material for farmland tailwater. In addition, the degradation pathway of DT during hydrothermal gasification (HTG) regeneration of the spent adsorbent was comprehensively discussed. The CHTG treatment enhanced the yield of gaseous products from RH and CM and produced AWBs with high adsorption capacities for DT. This provides a green and efficient technology for resource utilisation of agricultural waste and treatment of agricultural wastewater using pesticide residues.

Co-composting of biochar and nitrogen-poor organic residues: Nitrogen losses and fate of polycyclic aromatic hydrocarbons

Composting recycles nutrients and biodegrades organic pollutants, but often results in N leaching. Biochar can enhance the composting process and reduce N losses. Research, however, has focused on composting N-rich residues; also, information on the fate of biochar polycyclic aromatic hydrocarbons (PAHs) during composting is scarce. We explored the composting of biochar with N-poor organic residues as a strategy to reduce N losses and biochar PAHs. A small-scale composting experiment was performed with three treatments: 100% yard residues and two mixtures of 85% yard residues and 15% gasification- or pyrolysis-derived biochar. Temperatures were recorded daily during composting and Nlosses and changes in PAHs loads were calculated. Results across all treatments showed overall low N losses, likely caused by low temperatures and N contents, circumneutral pH values, and absence of leachate, and simultaneous immobilization and mineralization of PAH contents. Treatments with biochar showed a slower release of inorganic N (NO₃--N and NH₄⁺-N), although they also had overall lower inorganic N contents. This slower release of inorganic N may relate to biochar's high surface area. We conclude that biochar provides valuable benefits for N-poor composting, and that composting should be further explored as a promising strategy to reduce the contents of PAHs in biochar.

Using biochar to strengthen the removal of antibiotic resistance genes: Performance and mechanism

In this study, the excess activated sludge was used for pyrolysis to produce biochar with Ce modification. The removal process and mechanism of ampicillin resistance gene (ARG_Amp) by biochar was investigated. The results showed that when pyrolyzing the excess sludge at 400 °C, the organic components in the sludge could be partially pyrolyzed and complexed with Ce. By accepting electrons from phenol or quinone, persistent free radicals (PFRs) were formed on the surface of biochar. On the optimized conditions with the initial ARG_Amp concentration of 41.43 mg/L, the removal ratios of ARG_Amp by adsorption, PFRs, hydroxyl free radicals (·OH) by adding H₂O₂ were 28.37%, 8.26%, and 27.56%. No melted DNA was detected in the treated samples. The oxidation process by PFRs and ·OH can directly destroy the ARG_Amp structure. The phosphodiester bond in the base stacking structure and the phosphate bond in the nucleotide are the possible action sites of PFRs. Treated ARG_Amp products were in the form of base pair residues or short-chain double helix structures. ·OH can be added to the bases of nucleotide molecules to form highly active free radical adducts. They can initiate molecular dehydrogenation and intermolecular proton transfer, resulting in oxidation of the base to the scission of the phosphate sugar backbone.

Recent Advances on Innovative Materials from Biowaste Recycling for the Removal of Environmental Estrogens from Water and Soil

New technologies have been developed around the world to tackle current emergencies such as biowaste recycling, renewable energy production and reduction of environmental pollution. The thermochemical and biological conversions of waste biomass for bioenergy production release solid coproducts and byproducts, namely biochar (BC), hydrochar (HC) and digestate (DG), which can have important environmental and agricultural applications. Due to their physicochemical properties, these carbon-rich materials can behave as biosorbents of contaminants and be used for both wastewater treatment and soil remediation, representing a valid alternative to more expensive products and sophisticated strategies. The alkylphenols bisphenol A, octylphenol and nonylphenol possess estrogenic activity comparable to that of the human steroid hormones estrone, 17β-estradiol (and synthetic analog 17α-ethinyl estradiol) and estriol. Their ubiquitous presence in ecosystems poses a serious threat to wildlife and humans. Conventional wastewater treatment plants often fail to remove environmental estrogens (EEs). This review aims to focus attention on the urgent need to limit the presence of EEs in the environment through a modern and sustainable approach based on the use of recycled biowaste. Materials such as BC, HC and DG, the last being examined here for the first time as a biosorbent, appear appropriate for the removal of EEs both for their negligible cost and continuously improving performance and because their production contributes to solving other emergencies, such as virtuous management of organic waste, carbon sequestration, bioenergy production and implementation of the circular economy. Characterization of biosorbents, qualitative and quantitative aspects of the adsorption/desorption process and data modeling are examined.

Processing of natural fibre and method improvement for removal of endocrine-disrupting compounds

Persistent endocrine-disrupting compounds (EDCs) in bodies of water are a concern for human health and constitute an environmental issue, even if present in trace amounts. Conventional treatment systems do not entirely remove EDCs from discharge effluent. Due to the ultra-trace level of EDCs which affect human health and pose an environmental issue, developing new approaches and techniques to remove these micropollutants from the discharged effluent is vital. This review discusses the most common methods of eliminating EDCs through preliminary, primary, secondary and tertiary treatments. The adsorption process is favoured for EDC removal, as it is an economical and straightforward option. The NABC aspects, which are the need, approach, benefits and challenges, were analysed based on existing circumstances, highlighting biochar as a green and renewable adsorbent for the removal of organic contaminants. From the environmental point of view, the effectiveness of this method, which uses natural fibre from the kenaf plant as a porous and economical biochar material with a selected lignocellulosic biomass, provides insights into the advantages of biochar-derived adsorbents. Essentially, the improvement of the natural fibre as an adsorbent is a focus, using carbonisation, activation, and the physiochemical process to enhance the adsorption ability of the material for pollutants in bodies of water. This output will complement sustainable water management approaches presented in previous studies for combating the emerging pollutant crisis via novel green and environmentally safe options.

Electrochemical degradation performance and mechanism of dibutyl phthalate with hydrophobic PbO2 electrode

A polytetrafluoroethylene (PTFE) doped PbO₂ anode with a highly hydrophobicity was fabricated by electrodeposition method. In this process, vertically aligned TiO₂ nanotubes (TiO₂NTs) are formed by the anodic oxidation of Ti plates as an intermediate layer for PbO₂ electrodeposition. The characterization of the electrodes indicated that PTFE was successfully introduced to the electrode surface, the TiO₂NTs were completely covered with β-PbO₂ particles and gave it a large surface area, which also limited the growth of its crystal particles. Compared with the conventional Ti/PbO₂ and Ti/TiO₂NTs/PbO₂ electrode, the Ti/TiO₂NTs/PbO₂-PTFE electrode has enhanced surface hydrophobicity, higher oxygen evolution potential, lower electrochemical impedance, with more active sites, and generate more hydroxyl radicals (·OH), which were enhanced by the addition of PTFE nanoparticles. The electrocatalytic performance of the three electrodes were investigated using dibutyl phthalate (DBP) as the model pollutant. The efficiency of the DBP removal of the three electrodes was in the order: Ti/TiO₂NTs/PbO₂-PTFE > Ti/TiO₂NTs/PbO₂ > Ti/PbO₂. The degradation process followed the pseudo-first-order kinetic model well, with rate constants of 0.1326, 0.1266, and 0.1041 h^-1 for the three electrodes, respectively. The lowest energy consumption (6.1 kWh g^-1) was obtained after 8 h of DBP treatment using Ti/TiO₂NTs/PbO₂-PTFE compared to Ti/TiO₂NTs/PbO₂ (6.7 kWh g^-1) and Ti/PbO₂ (7.4 kWh g^-1) electrodes. Moreover, the effects of current density, initial pH and electrolyte concentration were investigated. Finally, the products of the DBP degradation process were verified based on gas chromatography-mass spectrometry analysis, and possible degradation pathways were described.

Characteristics of Cu(II)-modified aerobic granular sludge biocarbon in removal of doxycycline hydroxide

In this study, the biocarbon derived from aerobic granular sludge with different nutritive proportions was modified by Cu(NO₃)₂•3H₂O (Cu-BC) to improve its adsorption capacity of doxycycline hydrochloride (DOX). The surface area, pores, functional groups, and element composition of biocarbon were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectrometer, X-ray diffraction (XRD), the X-ray photoelectron spectrometer, and Fourier transform infrared spectrometry (FT-IR), respectively. Effects of DOX concentration, initial pH, and background electrolyte on adsorption effects of composite were analyzed. Furthermore, the adsorption kinetics, isotherm, thermodynamics, and diffusion model were investigated. Results demonstrated that biocarbons which were prepared with aerobic granular sludge under different nutritive proportions presented different performances. The BET specific surface area of Cu-NaAC/AGS-BC was 260.1592 m²/g, and the micropore volume was 0.054101 cm³/g. The BET specific surface area of Cu-GLC /AGS-BC was only 10.6821 m²/g, and the micropore volume was 0.008687 cm³/g. Both kinds of modified biochar contain a large number of oxygen-containing functional groups. The highest adsorption efficiency of Cu-BC could reach 99.54%. The adsorption of DOX on two modified biocarbons conforms to the pseudo-second-order dynamic model and Temkin isothermal model.

Removal of organochlorine pesticides using zerovalent iron supported on biochar nanocomposite from Nephelium lappaceum (Rambutan) fruit peel waste

Unique zerovalent iron (Fe⁰) supported on biochar nanocomposite (Fe⁰-B_RtP) was synthesized from Nephelium lappaceum (Rambutan) fruit peel waste and were applied for the simultaneous removal of 6 selected organochlorine pesticides (OCPs) from aqueous medium. During facile synthesis of Fe⁰-B_RtP, Rambutan peel extract was used as the green reducing mediator to reduce Fe²⁺ to zerovalent iron (Fe⁰), instead of toxic sodium borohydride which were used for chemical synthesis. For comparison, chemically synthesized Fe⁰-B_Che nanocomposite was also prepared in this work. Characterization study confirmed the successful synthesis and dispersion of Fe⁰ nanoparticles on biochar surface. Batch experiments revealed that Fe⁰-B_RtP and Fe⁰-B_Che nanocomposites combine the advantage of adsorption and dechlorination of OCPs in aqueous medium and up to 96-99% and 83-91% removal was obtained within 120 and 150 min, respectively at initial pH 4. Nevertheless, the reactivity of Fe⁰-B_Che nanocomposite decreased 2 folds after being aged in air for one month, whilst Fe⁰-B_RtP almost remained the same. Adsorption isotherm of OCPs were fitted well to Langmuir isotherm and then to Freundlich isotherm. The experimental kinetic data were fitted first to pseudo-second-order adsorption kinetic model and then to pseudo-first-order reduction kinetic model. The adsorption mechanism involves π-π electron-donor-acceptor interaction and adsorption is facilitated by the hydrophobic sorption and pore filling. After being reused five times, the removal efficiency of regenerated Fe⁰-B_Che and Fe⁰-B_RtP was 5-13% and 89-92%, respectively. The application of this Fe⁰-B_RtP nanocomposite could represent a green and low-cost potential material for adsorption and subsequent reduction of OCPs in aquatic system.

Accessing biochar's porosity using a new low field NMR approach and its impacts on the retention of highly mobile herbicides

Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on decay due to diffusion in internal magnetic field (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 μm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha^-1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.

Key factors and primary modification methods of activated carbon and their application in adsorption of carbon-based gases: A review

To achieve carbon neutrality, it is necessary to control carbon-based gas emissions to the atmosphere. Among the various carbon-based gas removal technologies reported to date, adsorption is considered one of the most promising because of its economic efficiency, reusability, and low energy consumption. Activated carbon is widely used to treat different types of carbon-based gases owing to its large specific surface area, abundant functional groups, and strong adsorption capacity. This paper reviews the recent research progress into activated carbon as an adsorbent for carbon-based gases. The key factors (i.e., specific surface area, pore structure, and surface functional groups) affecting the adsorption of carbon-based gases by activated carbon were analyzed. The main methods employed to modify activated carbon (i.e., surface oxidation, surface reduction, loading materials, and plasma modification methods) to improve its adsorption capacity are also discussed herein, along with the targeted applications of such material in the adsorption of different types of carbon-based gases (such as aldehydes, ketones, aromatic hydrocarbons, halogenated hydrocarbons, and carbon-based greenhouse gases). Finally, the future development directions and challenges of activated carbon are discussed. Our work will be expected to benefit the development of activated carbon exhibiting selective adsorption properties, and reduce the production costs of adsorbents.

Biochar protects hydrophilic dissolved organic matter against mineralization and enhances its microbial carbon use efficiency

A combination of biochar with exogenous organic material in soils is often used in practical farmland management. The objective of this study was to determine how biochar affects organic matter decomposition by studying the decomposition of ¹³C-labelled hydrophilic (Hi-) and hydrophobic (Ho-) dissolved organic matter (DOM) in acid and neutral soils during a 60-day incubation experiment. The proportions of carbon (C) mineralization in Hi-DOM with or without biochar addition were 32.6% or 34.5% in acid soil (P > 0.05) and 15.4% or 22.3% in neutral soil (P < 0.05), respectively. In contrast, those proportions of Ho-DOM-C mineralization with or without biochar addition were 20.0% or 21.4% in acid soil and 19.0% or 20.5% in neutral soil (P > 0.05), respectively. These results showed that biochar could protect Hi-DOM against mineralization in neutral soil but exhibited less effect on Ho-DOM mineralization in both acid and neutral soils. Additionally, biochar did not affect microbial incorporation of Hi- or Ho-DOM in acid and neutral soils. However, biochar notably improved the microbial carbon use efficiency (CUE) of Hi-DOM while it significantly reduced the CUE of Ho-DOM in neutral soil (P < 0.05), indicating that the effect of biochar on microbial CUE was related to organic matter type and soil pH. This study suggests that Hi-DOM can outperform Ho-DOM to decrease C loss and improve microbial CUE in neutral soil with biochar addition. This phenomenon could be due mainly to the different chemical compositions of Hi-DOM and Ho-DOM and their distinct microbial preference. These findings can provide references for biochar's ability to regulate the decomposition of organic matter.

Application of typical artificial carbon materials from biomass in environmental remediation and improvement: A review

Artificial carbon materials (ACMs), notably hydrochar, pyrochar, and artificial humic substances, etc., are considered to be sustainable and eco-friendly materials for environmental remediation and improvement. At present, almost relevant literature mainly focuses on biochar, and it is necessary to systematically summarize and expand studies on ACMs. ACMs are widely used to solve pollution problems in water and soil environments, as well as to remediate and improve soil quality. This review focuses on the following issues: 1. Reveal the synthetic mechanisms and compositional reactions effects of the charring process; 2. Define artificial humus as a novel class of ACMs and discuss the application of environmental remediation and relative enhancement effects; 3. Research the relative mechanisms and significance of ACMs during remediation process, involving removal and fixation of heavy metal ions (HMs)/organic pollutants (OPs), modification of soil physicochemical properties, affecting microbial community effects, and improving fertility for crop growth. Finally, the cost-benefit analysis and security-risk evaluation of ACMs are pointed out.

Application of pinewood waste-derived biochar for the removal of nitrate and phosphate from single and binary solutions

We developed biochar by pyrolysis of pinewood wastes at different temperatures and investigated its potential to nitrate and phosphate from single and binary solutions. An in-depth characterization of biochar was carried out to study its physical, surface morphological and chemical characteristics using X-ray diffraction, Fourier transform infrared and scanning electron microscopy analyses. The impact of pyrolysis temperatures (300-600 °C) on the biochar yield, the biochar's elemental composition, and its adsorption characteristics was examined. Biochar produced at 600 °C showed a maximum uptake for both nitrate and phosphate due to its high C content (63.8%), pore volume (0.201 cm³/g), surface area (204.2 m²/g) and reduced acidic binding groups. The influence of pH, initial solute concentrations, contact time on the removal of a single solute at a time by biochar was examined. Results revealed that pinewood-derived biochar had its maximum performance at pH 2, with predicted equilibrium uptakes of 20.5 and 4.20 mg/g for phosphate and nitrate, respectively at initial solute concentrations of 60 mg/L within 360 min. The single solute isotherm was studied using the Freundlich, Langmuir and Toth models, and kinetics was described using the pseudo-first and -second order models. While using dual-solutes, biochar showed preference towards phosphate as confirmed by high affinity factor. The dual-solute kinetic experiments showed that around 95% of phosphate was removed within 45 min, whereas it took 240 min to achieve 95% total nitrate removal from the mixture. Thus, the biochar removes phosphate preferentially with high selectivity as compared to nitrate.

Can biochar be an effective and reliable biostimulating agent for the remediation of hydrocarbon-contaminated soils?

Petroleum hydrocarbons represent one of the most common soil contaminants, whose presence poses a significant risk to soil biota and human health; for example, in Europe, hydrocarbon contamination accounts for more than 30% of contaminated sites. The use of biochar as a proposed alternative to the conventional remediation of soil contaminated with petroleum hydrocarbons has gained credence in recent times because of its cost-effectiveness and environmentally friendly nature. Biochar is a carbonaceous material produced by heating biomass in an oxygen-limited environment at high temperature. This review provides an overview of the application of biochar to remediate petroleum hydrocarbon-contaminated soils, with emphasis on the possibility of biochar functioning as a biostimulation agent. The properties of biochar were also examined. Furthermore, the mechanism, ecotoxicological impact and possible factors affecting biochar-based remediation are discussed. The review concludes by examining the drawbacks of biochar use in the remediation of hydrocarbon-contaminated soils and how to mitigate them. Biochar impacts soil microbes, which may result in the promotion of the degradation of petroleum hydrocarbons in the soil. Linear regression between bacterial population and degradation efficiency showed that R² was higher (0.50) and significant in treatment amended with biochar or both biochar and nutrient/fertiliser (p < 0.01), compared to treatment with nutrient/fertiliser only or no amendment (R² = 0.11). This suggest that one of the key impacts of biochar is enhancing microbial biomass and thus the biodegradation of petroleum hydrocarbons. Biochar represents a promising biostimulation agent for the remediation of hydrocarbon-contaminated soil. However, there remains key questions to be answered.

A review on efficient removal of phthalic acid esters via biochars and transition metals-activated persulfate systems

As emerging contaminants, PAEs (Phthalic Acid Esters or Phthalate Esters) have been extensively utilized in industrial production to soften the rigid plastics (plasticizers), and their related products are widely distributed in our daily life. The PAEs can readily transfer from the products to the surrounding environment due to not being chemically bound to the products. In this study, we analyzed the PAEs' properties, usage, and consumption in the world, as well as toxicity to human beings. As endocrine-disrupting chemicals (EDCs), PAEs can disturb the normal hormones reactions, resulting in developmental and reproductive problems. Thus, we have to concern the removal strategies of PAEs. We summarized two novel approaches, including biochars and persulfate (PS) oxidation for effectively removing PAEs in the literature. Their characteristics, removal mechanisms, and the main impact factors on the removal of PAEs were highlighted. Moreover, transition metal-activated PS showed good performance on PAEs degradation. Furthermore, the synergy of biochars and transition metals-PS can overcome the disadvantages of a single approach, and show better performance on the removal of PAEs. Finally, we put forward vital strategies to update two approaches (including the combined) for enhancing the removal of PAEs. It is expected that the researchers or scientists can get a hint on effectively remediating PAEs-contaminated sites via the biochars' sorption/transition metals-PS or the combined two from this review paper.

Sorption behaviour of xylene isomers on biochar from a range of feedstock

Inland oil spillage is one of the widespread sources of crude oil volatile organic compound emissions (CVEs) for which the long-term remedial solutions are often complex and expensive. This paper investigates the potential of a low-cost containment solution for contaminated solids by volatile organic compounds (VOCs) using biochar. The results of an extensive experimental investigation are presented on the sorption kinetics of xylene isomers (one type of the most frequently detected CVEs) on commercial biochar produced by prevalent feedstocks (wheat, corn, rice and rape straw as well as hardwood) at affordable temperatures (300-500°C). Chemical and physical properties of biochar were analysed in terms of elemental composition, scanning electron microscopy, specific surface area, ATR-FTIR spectra and Raman spectrometry. We show that for high-temperature biochar with similar surface chemistry, the sorption efficiency is mainly controlled by porous structure and pore size distribution. Biochar samples with higher specific surface area and higher volume of mesopores showed the highest sorption capacity (45.37-50.88 mg/g) since the sorbate molecules have more access to active sites under a greater intra-particle diffusion and elevated pore-filling. P-xylene showed a slightly higher sorption affinity to biochar compared to other isomers, especially in mesoporous biochar, which can be related to its lower kinetic diameter and simpler molecular shape. The sorption capacity of biochar produced at higher pyrolysis temperatures was found to be more sensitive to changes in ambient temperature due to dominant physical adsorption. Elovich kinetic model was found to be the best model to describe xylenes' sorption on biochar which indirectly indicates π-π stacking and hydrogen bonding as the main mechanism of xylene sorption on these types of biochar.

Effectively removing tetracycline from water by nanoarchitectured carbons derived from CO2: Structure and surface chemistry influence

Understanding of the correlation between physico-chemical property of adsorbent and the adsorption performance of contaminant is very significant for developing high-efficient materials to remove antibiotic contamination from water. In this work, a novel kind of carbon adsorbent (EC) derived from CO₂ and activated ECs with modified structure via a facile chemical method using H₂ and KOH were prepared. The synthetic carbon materials (EC, EC-H₂, and EC-KOH) were then applied to remove tetracycline (TC). The kinetics of adsorption for these three carbon materials all well fitted the pseudo-second-order kinetic model. The experimental data of adsorption isotherm had good compatibility with Langmuir and Freundlich models (R² > 0.90), but the Temkin model was the most applicable for all adsorbents (R² > 0.98). A super-high adsorption capacity of EC-KOH obtained from Langmuir fitting was 933.56 mg g^-1, which was much higher than that of EC-H₂ (538.91 mg g^-1) and EC (423.30 mg g^-1), possibly due to its larger specific surface area (S_BET), pore volume, and specific surface chemical structure. Moreover, it was found that surface functional groups and large aperture of adsorbents had a positive effect on adsorption rate. More adsorption sites and surface functional groups of adsorbents were beneficial to enhance the adsorption affinity. These results are of great benefit to the directional control of carbon structure to increase the adsorption performance in rate, capacity, and affinity of antibiotics.

Application of olive mill waste-based biochars in agriculture: Impact on soil properties, enzymatic activities and tomato growth

The olive oil industry is an important economic sector in Mediterranean countries. However, oil production is unfortunately accompanied by the generation of huge amounts of olive mill solid wastes (OMSW) and olive mill wastewater (OMWW). In the present study, a strategy is proposed for converting these olive mill wastes into biochar through pyrolysis, for their later use as an organic amendment in agriculture. Specifically, two biochars were prepared from the pyrolysis of OMSW at 500 °C, either alone or impregnated with OMWW (OMSW-B and I-OMSW-B). The characterization of the OMSW and I-OMSW samples and their derived biochars showed that the fixed carbon and ash contents in the feedstocks increased by 38% and 11% respectively for OMSW-B, and by 37% and 12% respectively for I-OMSW-B. Interestingly, the impregnation process significantly increased Na, P, K, Ca and Fe contents in the produced biochars. The effect of OMSW-B and I-OMSW-B amendments at different application dose (1%, 2.5% and 5% wt/wt) on the enzymatic activity of an agricultural soil was performed at laboratory scale with a pot test. The experimental results showed that phosphatase and urease activity increased with biochar application rate; amendment with I-OMSW-B at 1%, 2.5% and 5% enhanced the phosphatase activity by 63%, 142% and 285% and urease activity by 50%, 116% and 149%, respectively. On the other hand, dehydrogenase and protease activities were higher for the application rate of 2.5% biochar. Biochar amendment promoted tomatoes seedling growth after 10 weeks, which was highest in the application rates of 2.5% and 5% for both OMSW-B and I-OSMW-B. Thus, the produced biochars had great potential to be used as biofertilizers in agriculture.

Microcystin-LR sorption and desorption by diverse biochars: Capabilities, and elucidating mechanisms from novel insights of sorption domains and site energy distribution

This study accurately assessed microcystin-LR (MCLR)-trapping capabilities of diverse biochars based on sorption and sequential desorption (SDE), and elucidated MCLR sorption-desorption mechanisms from novel views of sorption domains and site energy distribution along sorption-SDE process. Results showed that maize straw biochar (MSB) and chicken manure biochar (CMB) excelled in trapping MCLR (91.0%-97.4% and 85.7%-96.4%, respectively, at 60-600 μg/L of initial MCLR amount), followed by their respective HCl-treated ones (HCMB, HSMB), while HCl-treated bamboo biochar and pine sawdust biochar poorly trapped MCLR (48.9%-77.8% for HBB, 22.6%-67.2% for HPSB). Non-partition sorption domains (NPSD) contributed more than partition sorption domain (PSD) to MCLR sorption by each biochar. Higher NPSD contribution to MCLR sorption in CMBs and MSBs than other biochars resulted from their higher pH_PZC and mesoporosity, which provided stronger electrostatic and pore-filling interaction for MCLR. Desorption hysteresis was weaken with rising aqueous MCLR amount for most biochars. Along SDE process, remaining MCLR in PSD of MSBs, HPSB and HBB could transfer to NPSD, thus desorption ratio continuously decreased with increasing desorption cycle. Differently, remaining MCLR in NPSD of CMBs converted into PSD during 1st-3rd desorption, causing fluctuated desorption ratio without obvious decrease as desorption cycle increased. These implied that MCLR in PSD was more easily desorbed than NPSD for each biochar. Site energy distribution dynamics supported the results of PSD and NPSD contribution changes along SDE. This study was greatly implicated in cost-efficient emergent MCLR-pollution remediation and deeply understanding MCLR sorption-desorption mechanisms of diverse biochars.

Biochar based sorptive remediation of steroidal estrogen contaminated aqueous systems: A critical review

Remediation of steroidal estrogens from aqueous ecosystems is of prevailing concern due to their potential impact on organisms even at trace concentrations. Biochar (BC) is capable of estrogen removal due to its rich porosity and surface functionality. The presented review emphasizes on the adsorption mechanisms, isotherms, kinetics, ionic strength and the effect of matrix components associated with the removal of steroidal estrogens. The dominant sorption mechanisms reported for estrogen were π-π electron donor-acceptor interactions and hydrogen bonding. Natural organic matter and ionic species were seen to influence the hydrophobicity of the estrogen in multiple ways. Zinc activation and magnetization of the BC increased the surface area and surface functionalities leading to high adsorption capacities. The contribution by persistent free radicals and the arene network of BC have promoted the catalytic degradation of adsorbates via electron transfer mechanisms. The presence of surface functional groups and the redox activity of BC facilitates the bacterial degradation of estrogens. The sorptive removal of estrogens from aqueous systems has been minimally reviewed as a part of a collective evaluation of micropollutants. However, to the best of our knowledge, a critique focusing specifically and comprehensively on BC-based removal of steroidal estrogens does not exist. The presented review is a critical assessment of the existing literature on BC based steroidal estrogen adsorption and attempts to converge the scattered knowledge regarding its mechanistic interpretations. Sorption studies using natural water matrices containing residue level concentrations, and dynamic sorption experiments can be identified as future research directions.

Reduction of chlordecone environmental availability by soil amendment of biochars and activated carbons from lignocellulosic biomass

Chlordecone (kepone or CLD) was formerly used in French West Indies as an insecticide. Despite its formal ban in 1993, high levels of this pesticide are still found in soils. As such, sequestering matrices like biochars or activated carbons (ACs) may successfully decrease the bioavailability of halogenated compounds like CLD when added to contaminated soils. The present study intends (i) to produce contrasted sequestering matrices in order to (ii) assess their respective efficiency to reduce CLD environmental availability. Hence, the work was designed following two experimental steps. The first one consisted at producing different sequestering media (biochars and ACs) via pyrolysis and distinct activation processes, using two lignocellulosic precursors (raw biomass): oak wood (Quercus ilex) and coconut shell (Cocos nucifera). The chemical activation was carried out with phosphoric acid while physical activation was done with carbon dioxide and steam. In the second step, the CLD environmental availability was assessed either in an OECD artificial soil or in an Antillean contaminated nitisol (i.e., 2.1^-1μg CLD per g of soil dry matter, DM), both amended with 5 wt% of biochar or 5 wt% of AC. These both steps aim to determine CLD environmental availability reduction efficiency of these media when added (i) to a standard soil material or (ii) to a soil representative of the Antillean CLD contamination context. Textural characteristics of the derived coconut and oak biochars and ACs were determined by nitrogen adsorption at 77 K. Mixed microporous and mesoporous textures consisting of high pore volume (ranging from 0.38 cm³.g^-1 to 2.00 cm³.g^-1) and specific (BET) surface areas from 299.9 m².g^-1 to 1285.1 m².g^-1 were obtained. Overall, soil amendment with biochars did not limit CLD environmental availability (environmental availability assay ISO/DIS 16751 Part B). When soil was amended with ACs, a significant reduction of the environmental availability in both artificial and natural soils was observed. AC soil amendment resulted in a reduced CLD transfer by at least 65% (P < 0.001) for all lignocellulosic matrices (excepted for coconut sample activated with steam, which displayed a 47% reduction). These features confirm that both pore structure and extent of porosity are of particular importance in the retention process of CLD in aged soil. Owing to its adsorptive properties, AC amendment of CLD-contaminated soils appears as a promising approach to reduce the pollutant transfer to fauna and biota.

Effects of endocrine disrupting chemicals in pigs

Endocrine-disrupting chemicals (EDCs) are compounds that interfere with the expression, synthesis, and activity of hormones in organisms. They are released into the environment from flame retardants and products containing plasticizers. Persistent pesticides, such as dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene, also disrupt the endocrine system through interaction with hormone receptors. Endogenous hormones, such as 17β-estradiol (E2), are released in the urine and feces of farm animals and seep into terrestrial and aquatic ecosystems through sewage. Pigs are widely used as animal models to determine the effects of EDCs because they are physiologically, biochemically, and histologically similar to humans. EDCs primarily disrupt the reproductive and nervous systems of pigs. Moreover, embryonic development during the prenatal and early postnatal periods is particularly sensitive to EDCs. Mycotoxins, such as zearalenone, are food contaminants that alter hormonal activities in pigs. Mycotoxins also alter the innate immune system in pigs, making them vulnerable to diseases. It has been reported that farm animals are exposed to various types of EDCs, which accumulate in tissues, such as those of gonads, livers, and intestines. There is a lack of an integrated understanding of the impact of EDCs on porcine reproduction and development. Thus, this article aims to provide a comprehensive review of literature regarding the effects of EDCs in pigs.

Formation and inhibition of polycyclic aromatic hydrocarbons from the gasification of cyanobacterial biomass in supercritical water

Polycyclic aromatic hydrocarbons (PAHs) formation and inhibition from supercritical water gasification (SCWG) of cyanobacterial biomass were investigated. High reaction temperature, long residence time, and low feedstock concentration favoured higher molecular weight (HMW) PAH formation. The total PAH yield reached 34.80 μg g^-1 at 500 °C, 22.5 MPa, and 10 min. The main PAHs formed in the liquid phase and the solid residue were 3-ring and 4-ring PAHs, which were generated from the cycloaddition reaction of lower molecular weight (LMW) PAHs. In addition, 2-ring PAHs were produced from the Diels-Alder reaction of phenols and unsaturated hydrocarbons. The possible control methods for PAH formation during the SCWG of cyanobacterial biomass were proposed. H₂O₂ addition effectively inhibited the reaction pathways underlying PAH formation, and the addition at more than 1.0% concentration suppressed H₂ production. The work revealed that the inhibition of PAHs was achieved in terms of improving the oxidisation condition during the SCWG process for converting wet biomass or organic wastes to energy sources.

ZnCl2 modified biochar derived from aerobic granular sludge for developed microporosity and enhanced adsorption to tetracycline

In this study, biochar derived from aerobic granular sludge was modified by ZnCl₂ (Zn-BC) to improve the adsorption performance of tetracycline (TC). The surface area, pores, and functional groups of Zn-BC were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) and the effects of initial pH, TC concentration, and temperature on TC adsorption performance were analyzed. At the same time, the adsorption kinetics, isotherms, thermodynamics and diffusion models were studied. The results showed that the BET surface area and micropore volume of Zn-BC were 852.41 m²·g^-1 and 0.086 cm³·g^-1, respectively. The maximum adsorption performance of TC was 93.44 mg·g^-1, and it was less influenced by pH. The adsorption of TC on Zn-BC agreed well with the pseudo-second-order model and the Langmuir isotherm. The thermodynamic parameters indicated that the adsorption process was a spontaneously endothermic reaction.

Effects of rice straw biochar on sorption and desorption of di-n-butyl phthalate in different soil particle-size fractions

Sorption of organic contaminants by biochar greatly affects their bioavailability and fate in soils. Nevertheless, very little information is available regarding the effects of biochar on sorption and desorption of organic contaminants in different soil particle-size fractions. In this study, di-n-butyl phthalate (DBP), a prevalent organic contaminant in agricultural soils, was taken as a model contaminant. The effects of biochar on DBP sorption and desorption in six particle-size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, clay, and humic acid fractions) of paddy soil were investigated using batch sorption-desorption experiments. A straw-derived biochar with high specific surface area (116 m²/g) and high content of organic matter (OM) rich in aromatic carbon (67%) was prepared. Addition of this biochar (1% and 5%) significantly promoted the sorption and retention of DBP in all the paddy soil particle-size fractions at environmentally relevant DBP concentrations (2-12 mg/L) with 1.2-132-fold increase of the K_d values. With increasing addition rates of biochar, DBP retention by the biochar enhanced. The biochar's effectiveness was remarkably influenced by the physicochemical properties of the soil particle-size fractions, especially, the OM contents and pore size showed the most striking effects. A parameter (r_kd) reflecting the biochar's effectiveness showed negative and positive correlations with OM contents and pore size of the soil particle-size fractions, respectively. Accordingly, strong effect of the biochar was found in the soil fractions with low OM contents and high pore size. The findings of this study gave insight into the effects and influencing factors of biochar on sorption and desorption of organic contaminants in soils at scale of various particle-size factions.

Filter Media-Packed Bed Reactor Fortification with Biochar to Enhance Wastewater Quality

Contamination of water sources by inappropriately disposed poorly treated wastewater from countryside establishments is a worldwide challenge. This study tested the effectiveness of retrofitting sand (Sa)- and gas–concrete (GC)-packed reactors with biochar (C) in removing turbidity, dissolved organic carbon (DOC), phosphate (PO43−), and total phosphorus (Ptot) from wastewater. The down-flow reactors were each intermittently loaded with 0.063 L/d for 399 days. In general, all reactors achieved <3 NTU (Nephelometric Turbidity Units) effluent turbidity (99% efficiency). GC reactors dominated in inlet PO43− (6.1 mg/L) and DOC (25.3 mg/L) reduction, trapping >95% and >60%, respectively. Compared to Sa (PO43−: 35%, DOC: 52%), the fortified sand (SaC) filter attenuated more PO43− (>42%) and DOC (>58%). Student t-tests revealed that C significantly improved the Sa PO43− (p = 0.022) and DOC (p = 0.034) removal efficacy. From regression analysis, 53%, 81%, and 85% PO43− sorption variation in Sa, C, and SaC, respectively, were explained by variation in their effluent pH measures. Similarly, a strong linear correlation occurred between PO43− sorption efficiency and pH of fortified (r > 0.7) and reference (r = 0.6) GC filters thus suggesting chemisorption mechanisms. Therefore, whereby only sand may be available for treating septic tank effluents, fortifying it with biochar may be a possible measure to improve its efficacy.

Effect of pyrolysis temperature and correlation analysis on the yield and physicochemical properties of crop residue biochar

The aim of this study was to evaluate how pyrolysis temperature influences the yield and physicochemical properties of biochar. We produced biochar from four feedstocks (wheat straw, corn straw, rape straw, and rice straw) pyrolyzed at 300, 400, 500, and 600 °C for 1 h, respectively. The results showed that all biochar yields decreased consistently with increasing temperature during pyrolysis and showed a steady decrease over 400 °C. Rice straw derived biochar had high yield superiority due to its higher content of ash. Pyrolysis temperature has significant effects on the properties of biochar; demonstrating a negative relationship with H, O, H/C, O/C, (O + N)/C, and functional groups, whilst having a positive relationship with C, ash, pH, electrical conductivity, and surface roughness. Higher pyrolysis temperature was beneficial to the formation of a more recalcitrant constitutions and crystal structure, making it available for material application.

Effects of pH and gallic acid on the adsorption of two ionizable organic contaminants to rice straw-derived biochar-amended soils

The existing form of ionizable organic contaminants (IOCs) could affect their adsorption characteristics to soil and biochar. In this study, 2 IOCs, namely, sulfadiazine and imazalil, were selected to study their adsorption by rice straw-derived biochar-amended soils, as well as the effect of pH and gallic acid on their adsorption. The results showed that the soil adsorption isotherms of the two ionizable organic contaminants could be fitted well by a linear equation and the Freundlich equation, and r² was more than 0.80. The adsorption coefficient (Kd) in the three kinds of soil ranged from 0.262 to 4.07 L kg^-1 for sulfadiazine and from 3.11 to 96.5 L kg^-1 for imazalil. After the addition of biochar, the adsorption of sulfadiazine and imazalil in the soil increased. The adsorption of sulfadiazine by biochar gradually decreased with the increase in pH; the adsorption of imazalil increased when the pH increased from 2 to 5 and then gradually decreased with increasing pH. Gallic acid enhanced the adsorption of the two IOCs to pure soil and biochar-amended soil.

Biochar and earthworms working in tandem: Research opportunities for soil bioremediation

Intensive use of agrochemicals is considered one of the major threats for soil quality. In an attempt to mitigate their side-effects on non-target organisms and soil functioning, many engineering and biological remediation methodologies are currently available. Among them, the use of biochar, a carbonaceous material produced from pyrolysing biomass, represents an attractive option enhancing both remediation and soil carbon storage potentials. Currently, activation of biochar with chemical or physical agents seeks for improving its remediation potential, but most of them have some undesirable drawbacks such as high costs and generation of chemical wastes. Alternatively, the use of biological procedures to activate biochar with extracellular enzymes is gaining acceptance mainly due to its eco-friendly nature and cost-effectiveness. In these strategies, microorganisms play a key role as a source of extracellular enzymes, which are retained on the biochar surface. Recently, several studies point out that soil macrofauna (earthworms) may act as a biological vector facilitating the adsorption of enzymes on biochar. This paper briefly introduces current biochar bioactivation methodologies and the mechanisms underlying the coating of biochar with enzymes. We then propose a new conceptual model using earthworms to activate biochar with extracellular enzymes. This new earthworm-biochar model can be used as a theoretical framework to produce a new product "vermichar", vermicompost produced from blended feedstock, earthworms, and biochar that can be used to improve soil quality and remove soil contaminants. This model can also be used to develop innovative in-situ "vermiremediation" technologies utilizing the beneficial effects of both earthworms and biochar. Since biochar may contain toxic chemicals generated during its production stages or later concentrated when applied to polluted soils, this paper also highlights the need for an ecotoxicological knowledge around earthworm-biochar interaction, promoting further discussion on suitable procedures for assessing the environmental risk of this conceptual model application in soil bioremediation.

The characterization of biochars derived from rice straw and swine manure, and their potential and risk in N and P removal from water

Nowadays, the plant residual derived biochars have been widely applied to remove nitrogen (N) and phosphorus (P) from water. However, the application of animal manure derived biochars in N and P removal was less studied. To compare the different efficiency and risk of plant residual- and animal manure-derived biochar in removing N and P from water, this study chose rice straw and swine manure as representative to produce biochar at 700 °C, and modified the produced biochar by MgCl₂. Then, the characteristics, removal efficiency and release of N and P of biochars were investigated. The results showed swine manure-biochars generally had higher ash content and cation exchange capacity (CEC), but lower pH and surface area relative to rice straw-biochars. Besides, MgCl₂ modification reduced the ash content and surface area of both raw biochars, whereas the pH, CEC and pore size were enhanced. Furthermore, this work demonstrated that ammonium and nitrate could be removed by all biochars to certain extent, and MgCl₂ modified biochars generally had higher removal efficiency. However, none of phosphate removal was achieved by all biochars. Additionally, the release of ammonium, nitrate and phosphate from biochars was observed, suggesting there might be a risk for applying biochars in N and P removal from water. Notably, the MgCl₂ modification seemed to accelerate N and P release from biochars. This work provided important information that the production and modification of biochars should be carefully designed for higher removal efficiency of pollutants. Meanwhile, the risk of released pollutants as well as the release mechanisms should be paid more attention in the future.

A pilot bioretention system with commercial activated carbon and river sediment-derived biochar for enhanced nutrient removal from stormwater

Bioretention is an effective technology for urban stormwater management, but the nutrient removal in conventional bioretention systems is highly variable. Thus, a pilot bioretention column experiment was performed to evaluate the nutrient control of systems with commercial activated carbon and river sediment-derived biochar. Significant chemical oxygen demand (COD) and total phosphorus (TP) leaching were found with the addition of activated carbon and biochar, but total nitrogen (TN) leaching was significantly improved when activated carbon was used as the medium. During a semi-synthetic runoff experiment, the bioretention systems containing two types of fluvial biochar showed relatively better COD and TN control (average mass removal efficiencies and cumulative removal efficiencies) than commercial activated carbon. However, the average TP mass removal efficiency with commercial activated carbon (95% ± 3%) was significantly higher than biochar (48% ± 20% and 56 ± 14%). The addition of biochar in the media increased the nitrogen removal efficiency, and the addition of activated carbon significantly increased the phosphorous removal efficiency. Therefore, both biochar and activated carbon are effective materials for bioretention, and fluvial biochar provides an alternative approach to comprehensively utilize river sediment.

The relative importance of different carbon structures in biochars to carbamazepine and bisphenol A sorption

Biochar, a carbon-rich material, has attracted immense attention owing to its applications in soil remediation. However, the mechanisms by which heterogeneous carbon structures of biochars immobilize organic contaminants are not yet fully understood. In this study, the noncondensed aromatic components in biochars were selectively removed through bleaching. Different techniques, such as ¹³C nuclear magnetic resonance, were applied to characterize the biochar compositions, and thus the role of the different carbon structures in organic contaminant sorption was discussed. The aromatic carbon structures in biochars were gradually developed and evolved from noncondensed to condensed structure with increasing pyrolytic temperatures from 300 to 700 °C. Based on elemental analysis, the carbon removed by bleaching decreased from 43.9% to 5.92% with increasing temperatures. After the surface area normalization of the apparent sorption, bleaching increased the sorption of carbamazepine and bisphenol A on biochars produced at 500 °C, but not for those produced at 300 and 700 °C. Bleaching removed noncondensed aromatics and enriched condensed aromatics, which resulted in increased sorption. However, bleaching also resulted in the blockage of micropores in biochars with abundant condensed aromatics, causing decreased sorption. The apparent sorption was determined by the balancing of these two opposite effects.

Combining bulk characterization and benzene polycarboxylic acid molecular markers to describe biochar properties

The physicochemical properties of biochar determined its sorption of organic contaminations, and the environmental aging process changed the biochar properties. However, the correlation between biochar heterogeneous properties and their sorption characteristics is unclear. In this study, peanut shell biochars were produced at 200-700 °C, and HNO₃/H₂SO₄ was used to oxidize 400 °C biochar for 2-10 h to simulate the enhanced aging process of biochar in the environment. Benzene polycarboxylic acid (BPCA) molecular markers, and bulk characterization were analyzed to describe biochar physicochemical properties and to further predict the sorption characteristics to bisphenol A (BPA). For pristine biochars, the mellitic acid/BPCAs (B6CA/BPCAs) increased with the raise of pyrolysis temperature and the H/C atomic ratio was positively correlated with benzenepentacarboxylic acid/B6CA (B5CA/B6CA) (P < 0.01), which indicated the increased aromatic condensation. After HNO₃/H₂SO₄ treatment, the aromaticity (H/C ratio) decreased while the highly condensed components in biochars were enriched (increased B6CA/BPCAs values). Multiple regression models were adopted to establish a quantitative relationship between biochar heterogeneous properties and their sorption of BPA. Both nonlinearity coefficient N values (N = 0.08 + 0.103 B5CA/B6CA + 0.721 (O + N)/C, R² = 0.985) and single-point sorption coefficients log K_d (log K_d = 1.236 + 0.006 BPCAs + 1.449 (O + N)/C, R² = 0.936) could be estimated combining molecular markers and polarity parameters for biochars.

Adsorption capacity of phenanthrene and pyrene to engineered carbon-based adsorbents produced from sewage sludge or sewage sludge-biomass mixture in various gaseous conditions

Adsorption of phenanthrene (PHE) and pyrene (PYR) by engineered carbon-based adsorbents produced from sewage sludge in an atmosphere of nitrogen (N₂) or carbon dioxide (CO₂) at temperatures of 500, 600, and 700 °C was investigated. The addition of willow to the SSL decreased the biochar adsorption capacity. However, there was an increase in the adsorption capacity after changing N₂ to CO₂. The addition of willow to SSL and the type of carrier gas affected the mechanism of adsorption. The adsorption of PHE and PYR on the SSL-derived adsorbents produced in N₂ occurred through pore filling. The adsorption on the SSL-derived adsorbents with willow followed the mechanism of π-π electron-donor-acceptor (EDA) interactions and hydrophobic interactions. A similar mechanism was observed with regard to the biochars produced from SSL in atmosphere of CO₂. For the SSL-derived adsorbents with willow in CO₂, the adsorption mechanism was observed to vary between PHE and PYR.

Sorption, degradation and bioavailability of oxyfluorfen in biochar-amended soils

To investigate the effects of biochar amendment on the environmental fate of oxyfluorfen in soils, we evaluated the sorption, degradation and bioavailability of oxyfluorfen in various amended soils. The results showed that different biochars, i.e., derived from peanuts (BCP), chestnuts (BCC), bamboo (BCB), maize straw (BCM), or rice hull (BCR), exhibited different sorption capacities for oxyfluorfen in following the order: BCR > BCB > BCM > BCC > BCP. The sorption constant (K_f value) of the three soils (loamy clay, sandy loam, and clay loam) ranged from 62 to 116 (μg/g)/(mg/L)ⁿ and increased by 2.0- to 3.2-fold after introduction of 2% BCR. Furthermore, oxyfluorfen degraded faster in BCR-amended soil than in unamended soil, i.e., degradation increased by 1.0- to 1.4-fold with addition of 2% BCR. Introduction of BCR also decreased the oxyfluorfen uptake by soybean plants by 18-63%, and the capacity of soybeans to absorb oxyfluorfen decreased over time. Amendment with 6 months-aged BCR soil increased the uptake of oxyfluorfen by soybean plants by 2.3-fold compared with freshly prepared BCR soil. After the aging process, the observed increase in oxyfluorfen bioavailability was attributed to the reduced adsorption capacity of aged biochar. Nevertheless, BCR was effective for sequestrating oxyfluorfen as demonstrated by the fact that the adsorption capacity of biochar-amended soil after six months of aging was still 1.5- to 2.5-fold greater compared with that of unamended soil. These results demonstrate that amendment with BCR can be an effective method to modify soil and thereby decrease oxyfluorfen contamination in food crops.