Biochar derived from red algae for efficient remediation of 4-nonylphenol from marine sediments

A systematic review on percarbonate-based advanced oxidation processes in wastewater remediation: From theoretical understandings to practical applications

Percarbonate encompasses sodium percarbonate (SPC) and composite in-situ generated peroxymonocarbonate (PMC). SPC emerges as a promising alternative to hydrogen peroxide (H2O2), hailed for its superior transportation safety, stability, cost-effectiveness, and eco-friendliness, thereby becoming a staple in advanced oxidation processes for mitigating water pollution. Yet, scholarly literature scarcely explores the deployment of percarbonate-AOPs in eradicating organic contaminants from aquatic systems. Consequently, this review endeavors to demystify the formation mechanisms and challenges associated with reactive oxygen species (ROS) in percarbonate-AOPs, alongside highlighting directions for future inquiry and development. The genesis of ROS encompasses the in situ chemical oxidation of activated SPC (including iron-based activation, discharge plasma, ozone activation, photon activation, and metal-free materials activation) and composite in situ chemical oxidation via PMC (namely, H2O2/NaHCO3/Na2CO3, peroxymonosulfate/NaHCO3/Na2CO3 systems). Moreover, the ROS generated by percarbonate-AOPs, such as •OH, O2•-, CO3•-, HO2•-, 1O2, and HCO4-, can work individually or synergistically to disintegrate target pollutants. Concurrently, this review systematically addresses conceivable obstacles posing percarbonate-AOPs in real-world application from the angle of environmental conditions (pH, temperature, coexisting substances), and potential ecological toxicity. Considering the outlined challenges and advantages, we posit future research directions to amplify the applicability and efficacy of percarbonate-AOPs in tangible settings. It is anticipated that the insights provided in this review will catalyze the progression of percarbonate-AOPs in water purification endeavors and bridge the existing knowledge void.

Amendment of Sargassum oligocystum bio-char with MnFe2O4 and lanthanum MOF obtained from PET waste for fluoride removal: A comparative study

The use of biomass and waste to produce adsorbent reduces the cost of water treatment. The bio-char of Sargassum oligocystum (BCSO) was modified with MnFe2O4 magnetic particles and La-metal organic framework (MOF) to generate an efficient adsorbent (BCSO/MnFe2O4@La-MOF) for fluoride ions (F-) removal from aqueous solutions. The performance of BCSO/MnFe2O4@La-MOF was compared with BCSO/MnFe2O4 and BCSO. The characteristics of the adsorbents were investigated using various techniques, which revealed that the magnetic composites were well-synthesized and exhibited superparamagnetic properties. The maximum adsorption efficiencies (BCSO: 97.84%, BCSO/MnFe2O4: 97.85%, and BCSO/MnFe2O4@La-MOF: 99.36%) were achieved under specific conditions of pH 4, F- concentration of 10 mg/L, and adsorbent dosage of 3, 1.5, and 1 g/L for BCSO, BCSO/MnFe2O4, and BCSO/MnFe2O4@La-MOF, respectively. The results demonstrated that the experimental data adheres to a pseudo-second-order kinetic model. The enthalpy, entropy, and Gibbs free energy were determined to be negative; thus, the F- adsorption was exothermic and spontaneous in the range of 25-50 °C. The equilibrium data of the process exhibited conformity with the Langmuir model. The maximum adsorption capacities of F- ions were determined as 10.267 mg/g for BCSO, 14.903 mg/g for the BCSO/MnFe2O4, and 31.948 mg/g for BCSO/MnFe2O4@La-MOF. The KF and AT values for the F- adsorption were obtained at 21.03 mg/g (L/mg)1/n and 100 × 10+9 L/g, indicating the pronounced affinity of the BCSO/MnFe2O4@La-MOF towards F- than other samples. The significant potential of the BCSO/MnFe2O4@La-MOF magnetic composite for F- removal from industrial wastewater, makes it suitable for repeated utilization in the adsorption process.

Synthesis, delineation and technological advancements of algae biochar for sustainable remediation of the emerging pollutants from wastewater-a review

The use of algae for value-added product and biorefining applications is enchanting attention among researchers in recent years due to its remarkable photosynthetic ability, adaptability, and capacity to accumulate lipids and carbohydrates. Algae biomass, based on its low manufacturing costs, is relatively renewable, sustainable, environmentally friendly and economical in comparison with other species. High production rate of algae provides a unique opportunity for its conversion to biochar with excellent physicochemical properties, viz. high surface area and pore volume, high adsorption capacity, abundant functional groups over surface, etc. Despite several potential algal-biochar, a detailed study on its application for removal of emerging contaminants from wastewater is limited. Therefore, this technical review is being carried out to evaluate the specific elimination of inorganic and organic pollutants from wastewater, with a view to assessing adsorption performances of biochar obtained from various algae species. Species-specific adsorption of emerging pollutants from wastewater have been discussed in the present review. The promising methods like pyrolysis, gasification, dry and wet torrefaction for the production of algae biochar are highlighted. The strategies include chemical and structural modifications of algae biochar for the removal of toxic contaminants have also been considered in the current work. The overall aim of this review is to confer about the synthesis, technological advancements, delineation and application of algae biochar for the treatment of wastewater.

Research advances on production and application of algal biochar in environmental remediation

Algae, comprising microalgae and macroalgae, have emerged as a promising feedstock for the production of functional biochar. Recently, the application of algal biochar in environmental remediation gains increasing attention. This review summarizes research advancements in the synthesis and application of algal biochar, a versatile and sustainable material for environmental remediation ranging from wastewater treatment to soil improvement. Algal biochar can be prepared by pyrolysis, microwave-assisted pyrolysis, and hydrothermal carbonization. Physical and chemical modifications have proven to be effective for improving biochar properties. Algal biochar is promising for removing diverse pollutants including heavy metals, organic pollutants, and microplastics. The role in soil improvement signifies a sustainable approach to enhancing soil structure, nutrient retention, and microbial activity. Research gaps are identified based on current understanding, necessitating further exploration into variations in biochar characteristics, the performance improvement, large-scale applications, and the long-term evaluation for environmental application. This review provides a better understanding of algal biochar as a sustainable and effective tool in environmental remediation.

Phytoremediation of contaminated sediment combined with biochar: Feasibility, challenges and perspectives

The accumulation of contaminants in sediments is accelerated by human activities and poses a major threat to ecosystems and human health. In recent years, various remediation techniques have been developed for contaminated sediments. In this review, a bibliometric analysis of papers on sediment remediation indexed in the WOS database between 2009 and 2023 was conducted using VOSviewer. We describe the development of biochar and plants for sediment contaminant removal. However, the single processes of biochar remediation and phytoremediation can be impeded by (i) low efficiency, (ii) poor tolerance of plants towards pollutants, (iii) difficulty in biochar to degrade pollutants, and (iv) biochar aging causing secondary pollution. Fortunately, combination remediation, realized through the combination of biochar and plants, can overcome the shortcomings of their individual applications. Therefore, we suggest that the remediation of contaminants in sediments can be accomplished by combining biochar with macrophytes and considering multiple limiting factors. Here, we explore the challenges that co-remediation with biochar and macrophytes will face in achieving efficient and sustainable sediment remediation, including complex sediment environments, interaction mechanisms of biochar-macrophyte-microorganisms, emerging pollutants, and integrated life cycle assessments, which can provide references for combined biochar and plant remediation of sediments in the future.

Nonylphenol and its derivatives: Environmental distribution, treatment strategy, management and future perspectives

In recent years, emerging pollutants, including nonylphenol (NP) and nonylphenol ethoxylate (NPE), have become a prominent topic. These substances are also classified as persistent organic pollutants. NP significantly affects the hormone secretion of organisms and exhibits neurotoxicity, which can affect the human hippocampus. Therefore, various countries are paying increased attention to NP regulation. NPEs are precursors of NPs and are widely used in the manufacture of various detergents and lubricants. NPEs can easily decompose into NPs, which possess strong biological and environmental toxicity. This review primarily addresses the distribution, toxicity mechanisms and performance, degradation technologies, management policies, and green alternative reagents of NPs and NPEs. Traditional treatment measures have been unable to completely remove NP from wastewater. With the progressively tightening management and regulatory policies, identifying proficient and convenient treatment methods and a sustainable substitute reagent with comparable product effectiveness is crucial.

The magic of algae-based biochar: advantages, preparation, and applications

Compared with other biomass sources, the use of algae as a raw material to prepare biochar (BC) has important advantages including safety, high yield and economy. The protein content of algae cells is as high as 3.2 mg DCW/L, and the graphitic-N and N-O functional groups generated by the pyrolysis of proteins could effectively activate free radicals. Combined with the generated pore structure, the electron transfer/exchange capability was enhanced, which is conducive to improving its catalytic performance. Algae as a natural N source, the manuscript analyzed the surface properties and physicochemical properties of algae-based BC, and investigated its degradation effect on organic/inorganic pollutants in wastewater. Subsequently, the effect of nitrogen-doped BC on the adsorption/catalysis capacity was discussed. Finally, the directed preparation of algae-based BC applied in different scenarios was summarized. Algae-based BC has the property of N doping, which broadens its application efficiency in the environmental field. Overall, this manuscript reviews how to achieve efficient utilization of algae-based BC in wastewater.

Enhanced copper (II) bioremediation from wastewater using nano magnetite (Fe3O4) modified biochar of Ascophyllum nodosum

Despite the remarkable Cu(II) sorption biochar potential, it is challenging to desorb them for repeated biochar usage. The present study aims to develop engineered biochar by polarizing Ascophyllum nodosum (seaweed) biomass and magnetizing it with Fe3O4 nanoparticles coating. SEM, EDX, XRD, BET, and FT-IR helped to characterize engineered biochar. Unlike conventional, magnetite biochar exhibited a significant Cu(II) removal potential from an aqueous solution at pH 5. The native and magnetic biochar removal efficiency was 75.2 % (36.99 mgg-1) and 90.27% (45.13 mgg-1), respectively. No significant change in temperature effect was observed. Adsorption study showed that magnetic biochar followed the Langmuir isotherm model with Qmax 53.19 mgg-1. Adsorption kinetics study indicates that magnetic biochar chemisorption dominates over physisorption. Thus, this study shows that seaweed-derived modified biochar could be the best alternative bioresource for removing heavy metals from wastewater. It can be reused to reduce the overall treatment cost of the process.

Pyrolysis processes affecting polycyclic aromatic hydrocarbon profile of pineapple leaf biochar exemplified by atmosphere/temperature and heteroatom doping

The content of polycyclic aromatic hydrocarbons in pineapple leaf biochar was examined as a function of pyrolysis atmosphere (CO₂ or N₂), pyrolysis temperature (300-900 °C), and heteroatom (N, B, O, P, NP, or NS) doping. Without doping, the polycyclic aromatic hydrocarbon production was maximal (1332 ± 27 ng/g) in CO₂ at 300 °C and minimal (157 ± 2 ng/g) in N₂ at 700 °C. The main components naphthalene and acenaphthylene accounted for about 91% of the total polycyclic aromatic hydrocarbon in the biochar prepared under CO₂ at 300 °C. Under the maximal polycyclic aromatic hydrocarbon production conditions (CO₂, 300 °C), doping decreased the total hydrocarbon content by 49% (N), 61% (B), 73% (O), 92% (P), 93% (NB), and 96% (NS). The results shed new light on the management of polycyclic aromatic hydrocarbons in BC production by controlling the pyrolysis atmosphere and temperature in addition to heteroatom doping. Results significantly contributed to the development of circular bioeconomy.

Effects of pyrolysis conditions and heteroatom modification on the polycyclic aromatic hydrocarbons profile of biochar prepared from sorghum distillery residues

The formation of 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs) in sorghum distillery residue-derived biochar (SDRBC) was evaluated under different thermochemical pyrolysis conditions of carbonization atmosphere (N2 or CO2), temperature (300-900 °C) and doping with nonmetallic elements, i.e., N, B, O, P, N + B, and N + S. The results indicated that without surface modification, PAHs formation was 944 ± 74 ng g-1, the highest level, and 181 ± 16 ng g-1, the lowest level, at 300 °C in N2 and CO2 atmosphere, respectively. Boron doping of SDRBC significantly reduced the PAHs content (by 97%) under N2 at 300 °C. Results demonstrated that boron modified SDRBC exhibited the highest degree of PAH reduction. Combined pyrolysis temperature and atmosphere in addition to heteroatom doping is a robust and viable strategy for efficient suppression of PAHs formation and high-value utilization of pyrolysis products of low carbon footprint.

Current application of seaweed waste for composting and biochar: A review

To address the origins of ocean acidification, seaweed aquaculture is emerging as a key biosequestration strategy. Nevertheless, seaweed biomass is involved in developing food and animal feed, whereas seaweed waste from commercial hydrocolloid extraction is dumped in landfills, which together limit the carbon cycle and carbon sequestration. This work sought to evaluate the production, properties, and applications of seaweed compost and biochar to strengthen the "carbon sink" implications of aquaculture sectors. Due to their unique characteristics, the production of seaweed-derived biochar and compost, as well as their existing applications, are distinct when compared to terrestrial biomass. This paper outlines the benefits of composting and biochar production as well as proposes ideas and perspectives to overcome technical shortcomings. If properly synchronized, progression in the aquaculture sector, composting, and biochar production, potentially promote various Sustainable Development Goals.

Activation of calcium peroxide by nitrogen and sulfur co-doped metal-free lignin biochar for enhancing the removal of emerging organic contaminants from waste activated sludge

The accumulation of emerging organic contaminants (EOCs) in waste activated sludge (WAS) is a global concern. In this study, a multi-heteroatom nitrogen and sulfur was successfully embedded into lignin-based biochar (N-S-LGBC) and used it to activate calcium peroxide (CP) for the degradation of 4-nonylphenol (4-NP) in WAS. N-S-LGBC/CP was effective in degrading 85 % of 4-NP within 12 h through the activation of CP owing to hydroxyl radicals and singlet oxygen species generated from the synergism among pyrrolic-N, thiophenic-S, and lattice oxygen, i.e., active sites responsible for 4-NP degradation. These results highlight substrate biodegradability for subsequent bioprocesses that improves WAS treatment in EOC degradation by the N-S-LGBC/CP-mediated process. There was abundance of distinct Aggregatilinea genus within the phylum Chloroflexi during N-S-LGBC/CP treatment, indicating high 4-NP pretreatment efficiency in WAS. This work provides a new understanding of N-S-co-doped carbocatalysts in green and sustainable hydroxyl radical-driven carbon advanced oxidation (HR-CAOP) platforms for WAS remediation.

Nitrogen and boron co-doped lignin biochar for enhancing calcium peroxide activation toward organic micropollutants decontamination in waste activated sludge and related microbial structure dynamics

This study synthesized dual heteroatom nitrogen and boron-co-doped lignin-based biochar (NB-LGBC) for calcium peroxide (CP) activation to enhance the removal of organic micropollutants (OMPs), namely, 4-nonylphenol (4-NP) from waste activated sludge (WAS). NB-LGBC/CP enhanced 4-NP degradation by arriving at 83 % removal in 12 h. The NB-LGBC/CP system degraded 4-NP via a synergistic interaction (HO•, O₂^•- radicals, and singlet oxygen) and electron transfer due to the N-B-C bonding configurations. Results of fluorescence excitation-emission matrix (FEEM) analysis revealed significantly increase in biodegradable organics from treated WAS mixture. NB-LGBC/CP treatment enriched alkaliphilic bacterium associated with the predominance of the genus Desulfonatronum within the phylum Proteobacteria in the WAS, which improved the biological treatment capacity of 4-NP. Thus, NB-LGBC in HR-CAOP will be a novel approach for WAS decontamination.

Advanced oxidation processes for water purification using percarbonate: Insights into oxidation mechanisms, challenges, and enhancing strategies

Percarbonate (SPC) has drawn considerable attention due to its merits in the safety of handling and transport, stability, and price as well as environmental friendliness, which has been extensively applied in advanced oxidation processes (AOPs) for water decontamination. Nevertheless, comprehensive information on the application of SPC-AOPs for the treatment of organic compounds in aquatic media is scarce. Hence, the focus of this review is to shed light on the mechanisms of reactive oxygen species (ROS) evolution in typical SPC-AOPs (i.e., Fenton-like oxidation, photo-assisted oxidation, and discharge plasma-involved oxidation processes). These SPC-AOPs enable the formation of multiple reactive species like hydroxyl radical (^•OH), superoxide radical (O₂^•-), singlet oxygen (¹O₂), carbonate radicals (CO₃^•-), and peroxymonocarbonate (HCO₄^-), which together or solely contribute to the degradation of target pollutants. Simultaneously, the potential challenges in practical applications of SPC-AOPs are systematically discussed, which include the influence of water quality parameters, cost-effectiveness, available active sites, feasible activation approaches, and ecotoxicity. Subsequently, enhancing strategies to improve the feasibility of SPC-AOPs in the practical implementation are tentatively proposed, which can be achieved by introducing reducing and chelating agents, developing novel activation approaches, designing multiple integrated oxidation processes, as well as alleviating the toxicity after SPC-AOPs treatment. Accordingly, future perspectives and research gaps in SPC-AOPs are elucidated. This review will hopefully offer valuable viewpoints and promote the future development of SPC-AOPs for actual water purification.

The remediation of di-(2-ethylhexyl) phthalate-contaminated sediments by water hyacinth biochar activation of calcium peroxide and its effect on cytotoxicity

The presence of di-(2-ethylhexyl) phthalate (DEHP) in the aquatic systems, specifically marine sediments has attracted considerable attention worldwide, as it enters the food chain and adversely affects the aquatic environment and subsequently human health. This study reports an efficient carbocatalytic activation of calcium peroxide (CP) using water hyacinth biochar (WHBC) toward the efficient remediation of DEHP-contaminated sediments and offer insights into biochar-mediated cellular cytotoxicity, using a combination of chemical and bioanalytical methods. The pyrolysis temperature (300-900 °C) for WHBC preparation significantly controlled catalytic capacity. Under the experimental conditions studied, the carbocatalyst exhibited 94% of DEHP removal. Singlet oxygen (¹O₂), the major active species in the WHBC/CP system and electron-rich carbonyl functional groups of carbocatalyst, played crucial roles in the non-radical activation of CP. Furthermore, cellular toxicity evaluation indicated lower cytotoxicity in hepatocarcinoma cells (HepG2) after exposure to WHBC (25-1000 μg mL^-1) for 24 h and that WHBC induced cell cycle arrest at the G2/M phase. Findings clearly indicated the feasibility of the WHBC/CP process for the restoration of contaminated sediment and contributing to understanding the mechanisms of cytotoxic effects and apoptotic of carbocatalyst on HepG2.

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar for enhancing the degradation of sulfathiazole antibiotics by peroxymonosulfate and its effects on bacterial community dynamics

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar (denoted as N-CSBC, O-CSBC, and B-CSBC, respectively) were fabricated in a one-step pyrolysis process to promote peroxymonosulfate (PMS) activation for the elimination of sulfathiazole (STZ) from aquaculture water. B-CSBC exhibited remarkably high catalytic activity with 92% of STZ degradation in 30 min attributed to the presence of meso-/micro-pores and B-containing functional groups (including B-N, B-C, and B₂O₃ species). Radical quenching tests revealed SO₄^•-, HO•, and ¹O₂ being the major electron acceptors contributing to STZ removal by PMS over B-CSBC catalyst. The B-CSBC catalyst has demonstrated high sustainability in multiple consecutive treatment cycles. High salinity and the presence of inorganic ions such as chloride, enhanced the performance of the sulfate radical-carbon-driven advanced oxidation processes (SR-CAOPs) as pretreatment strategy that significantly facilitated the removal of STZ from aquaculture water. Furthermore, a potential sulfonamide-degrading microorganism, Cylindrospermum_stagnale, belonging to the phylum Cyanobacteria, was the dominant functional bacteria according to the results of high-throughput 16S rRNA gene sequencing conducted after the B-CSBC/PMS treatment. This study provides new insights into the SR-CAOP combined with bioprocesses for removing STZ from aqueous environments.

Ecological responses of coral reef to polyethylene microplastics in community structure and extracellular polymeric substances

The relationships and interactions between extracellular polymeric substances (EPS) and microplastics (MPs) in coral reef ecosystems were symmetrically investigated. The current study aims to investigate the responses of scleractinian coral (Goniopora columna) to exposure of model MPs, exemplified by polyethylene (PE), in the size range of 40-48 μm as affected by MPs concentration of MP in the range between 0 and 300 mg L^-1 for 14 days. The structure of EPS-associated microbial community was studied using a series of techniques including high-throughput sequencing of 16 S rRNA, transmission electron microscopy (TEM), hydrodynamic diameter, surface charge (via zeta potential), X-ray diffraction (XRD), attenuated total reflectance‒Fourier transform infrared (ATR‒FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and fluorescence excitation-emission matrix (FEEM) spectroscopy. Microbial interactions between PE-MPs and coral caused aggregation and formation of EPS matrix, which resulted in increase and decrease in the relative abundance of Donghicola (Proteobacteria phylum) and Marivita (Proteobacteria phylum) in PE-MP-associated EPS, respectively. Particle size, electrostatic interactions, and complexation with the functional groups of the EPS-based matrix affected the humification index. FEEM spectroscopy analyses suggested the presence of humic- and fulvic-like fluorophores in EPS and dissolved organic matter (DOM) in PE-MP-derived DOM. The findings provided insights into the potential environmental implications of coral-based EPS and co-existing microbial assemblages due to EPS-PE-MP-microbiome interactions throughout the dynamic PE-MP exposure process.

Degradation of 4-nonylphenol in marine sediments using calcium peroxide activated by water hyacinth (Eichhornia crassipes)-derived biochar

The contamination of marine sediments by 4-nonylphenol (4-NP) has become a global environmental problem, therefore there are necessaries searching appropriate and sustainable remediation methods for in-situ applications. Herein, water hyacinth [(WH) (Eichhornia crassipes)]-derived metal-free biochar (WHBC) prepared at 300-900 °C was used to promote the calcium peroxide (CP)-mediated remediation of 4-NP-contaminaed sediments. At [CP] = 4.37 × 10^-4 M, [WHBC] = 1.5 g L^-1, and pH = 6.0, the degradation of 4-NP was 77% in 12 h following the pseudo-first order rate law with rate constant (k_obs) of 4.2 × 10^-2 h^-1. The efficient 4-NP degradation performance and reaction mechanisms of the WHBC/CP system was ascribed to the synergy between the reactive species (HO• and ¹O₂) at the WHBC surface on which there were abundant electron-rich carbonyl groups and defects/vacancies in the catalyst structure provides active sites, and the ability of the graphitized carbon framework to act as a medium for electron shuttling. According to microbial community analysis based on amplicon sequence variants, bacteria of the genus Solirubrobacter (Actinobacteria phylum) were dominant in WHBC/CP-treated sediments and were responsible for the biodegradation of 4-NP. The results showed great promise and novelty of the hydroxyl radical-driven carbon advanced oxidation processes (HR-CAOPs) that relies on the value-added utilization of water hyacinth for contaminated sediment remediation in achieving circular bioeconomy.

Performance and bacterial community dynamics of lignin-based biochar-coupled calcium peroxide pretreatment of waste-activated sludge for the removal of 4-nonylphenol

Waste activated sludge contaminated with high levels of 4-nonylphenol (4-NP) is a major environmental concern. We have synthesized lignin-based biochar (LGBC) for use as a carbocatalyst in calcium peroxide (CP)-mediated sewage sludge pretreatment. Treatment of sewage sludge with 3.1 × 10^-4 M of CP and 3.0 g L^-1 of LGBC removed 76% of 4-NP in 12 h, which were 3.8 and 2.4 times higher than that with the LGBC and CP alone, respectively. There was synergy between reactive oxygen species (HO•, O₂^•-, and ¹O₂) and graphitic frameworks of LGBC. Pretreatment using the LGBC/CP system enhanced the release of biodegradable organic xenobiotics from the sludge. LGBC/CP enriched Proteobacteria and Thermostilla bacterial consortium (Planctomycetes) in the sludge and promoted 4-NP biodegradation. This work provides new insights into the chemical and biological mechanisms by which LGBC promotes 4-NP biodegradation in waste activated sludge via hydroxyl radical-driven carbon advanced oxidation pretreatment.

Exposure of Goniopora columna to polyethylene microplastics (PE-MPs): Effects of PE-MP concentration on extracellular polymeric substances and microbial community

Although the pollution of coral reefs by microplastics (MPs) is an environmental problem of global significance, the effects of MP concentration on scleractinian corals remain largely underexplored. Herein, we exposed a representative scleractinian coral (Goniopora columna) to different concentrations (5-300 mg L^-1) of polyethylene microplastics (PE-MPs; 40-48 μm) over seven days and evaluated the changes in microbial community and extracellular polymeric substances (EPS) using fluorescence excitation-emission matrix spectroscopy and amplicon sequence variants (ASV). At a PE-MP concentration of 300 mg L^-1, the relative abundance of Bacillus (Firmicutes phylum) and Ruegeria (Proteobacteria phylum) in PE-MP-associated EPS increased and decreased, respectively, while the effects of exposure depended on the particle size of the extracellular polymeric substance (EPS)-based matrix and the humification index. Humic- and fulvic-like substances were identified as critical EPS components produced by microbial activity. The results have shed new insights into short-term responses of G. columna during exposure to different PE-MP concentrations and reveal important coral-MP-microbiome interactions in coral reef ecosystems. Results demonstrated that the coral-MPs interactions should be further evaluated to gain a deeper understanding of the underlying ecotoxicological risks.

Metal-free carbocatalysts derived from macroalga biomass (Ulva lactuca) for the activation of peroxymonosulfate toward the remediation of polycyclic aromatic hydrocarbons laden marine sediments and its impacts on microbial community

Potential toxic chemicals, specifically, polycyclic aromatic hydrocarbons (PAHs), are major sediment contaminants. Herein, green seaweed (Ulva lactuca) was used as a feedstock and pyrolyzed at temperature in the range between 300 and 900 °C. The metal-free carbocatalyst (GSBC) for peroxymonosulfate (PMS) activation to degrade PAHs contaminated sediments was studied. The effects of GSBC‒PMS treatment on microbial community abundance was studied as well. The pyrolysis temperature of GSBC preparation affected the PMS activation performance. Results show that GSBC700 exhibited remarkable catalytic characteristics in PAHs degradation by effective activation of PMS. The results also demonstrated that the sulfate radical-carbon-driven advanced oxidation processes (SR-CAOP) reaction achieved 87% and apparent rate constant (k_obs) of 6.3 × 10^-2 h^-1 of total PAHs degradation in 24 h at 3.3 g/L of GSBC, PMS dose of 1 × 10^-4 M, and pH 3.0. The degradation of 2-, 3-, 4-, 5-, and 6-ring PAHs was 84, 83, 83, 80, and 89%, respectively. The synergetic effect established between GSBC and PMS enhanced the formation of ROSs, namely, SO₄^-, HO, and ¹O₂, which were major species contributing to PAHs degradation. The synergistic effect of π‒π stacking structure and graphitization of GSBC formed electron shuttle, which contributed to PAHs degradation performance. Microbial community structure analyses in the GSBC‒PMS treated sediments showed that the relative abundance of Lactobacillus_rhamnosus species, most of which belonged to the Lactobacillus genus and Firmicutes phylum, which aided in continuing PAHs biodegradation post GSBC‒PMS treatment. Therefore, GSBC can be a promising carbocatalyst produced via biomass-to-biochar conversion as biowaste-to-energy source used in the SR-CAOP-mediated process for sediment remediation.

Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications

Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.

Advances on tailored biochar for bioremediation of antibiotics, pesticides and polycyclic aromatic hydrocarbon pollutants from aqueous and solid phases

Biochar is gaining incredible importance for remediation applications due to their attractive removal properties. Moreover, it is becoming ecofriendly, cost-effective and sustainable bioadsorbents towards replacing expensive activated carbons. Studies reveal biochar effectiveness for removal of important and potentially severe organic pollutants such as antibiotics and pesticides. Recent research advancements on biochar modification (physical, chemical and biological) opens greater opportunity to form tailored biochar with improved surface properties than their native forms for offering better removal efficiencies. Further attentions paid towards emergent new modification methods to cover broad-spectrum pollutants using tailored biochar. Current review aims to summarize recent updates upon biochar tailoring, comparative account of tailored biochars removal efficiencies with respect to their native forms and to provide in-depth discussion covering specific interactions of tailored biochars with antibiotics, polycyclic aromatic hydrocarbons (PAHs) and pesticides for their effective removals and degradation from polluted environments. Application of inducer compounds e.g., peroxymonosulfate and sodium percarbonate further improved the biochar role towards degradation of toxic organic pollutants into their less or nontoxic forms. Biochar engineered with specific metals enable them for the same role without inducer compounds. Moreover, microbial interactions with biochar not only improve the bioremediation level further but also degrade the pollutants from the environment and open up better environmental and socio-economic prospects. Application of green, cost-effective and sustainable biochar for remediation of environmentally potential organic pollutants offers economical treatment methods as well as safe environment. These benefits are inline with global trends towards developing a sustainable process for biocircular economy.

Industrial CO2 Capture by Algae: A Review and Recent Advances

The problem of global warming and the emission of greenhouse gases is already directly affecting the world’s energy. In the future, the impact of CO2 emissions on the world economy will constantly grow. In this paper, we review the available literature sources on the benefits of using algae cultivation for CO2 capture to decrease CO2 emission. CO2 emission accounts for about 77% of all greenhouse gases, and the calculation of greenhouse gas emissions is 56% of all CO2 imports. As a result of the study of various types of algae, it was concluded that Chlorella sp. is the best at capturing CO2. Various methods of cultivating microalgae were also considered and it was found that vertical tubular bioreactors are emerging. Moreover, for energy purposes, thermochemical methods for processing algae that absorb CO2 from flue gases were considered. Of all five types of thermochemical processes for producing synthesis gas, the most preferred method is the method of supercritical gasification of algae. In addition, attention is paid to the drying and flocculation of biofuels. Several different experiments were also reviewed on the use of flue gases through the cultivation of algae biomass. Based on this literature review, it can be concluded that microalgae are a third generation biofuel. With the absorption of greenhouse gases, the growth of microalgae cultures is accelerated. When a large mass of microalgae appears, it can be used for energy purposes. In the results, we present a plan for further studies of microalgae cultivation, a thermodynamic analysis of gasification and pyrolysis, and a comparison of the results with other biofuels and other algae cultures.

A state-of-the-art review on algae pyrolysis for bioenergy and biochar production

Algae, as a feedstock with minimum land footprint, is considered a promising biomass for sustainable fuels, chemicals, and materials. Unlike lignocellulosic biomass, algae consist mainly of lipids, carbohydrates, and proteins. This review focusses on the bio-oil and biochar co-products of algae-pyrolysis and presents the current state-of-the-art in the pyrolysis technologies and key applications of algal biochar. Algal biochar holds potential to be a cost-effective fertilizer, as it has high P, N and other nutrient contents. Beyond soil applications, algae-derived biochar has many other applications, such as wastewater-treatment, due to its porous structure and strong ion-exchange capacity. High specific capacitance and stability also make algal biochar a potential supercapacitor material. Furthermore, algal biochar can be great catalysts (or catalyst supports). This review sheds light on a wide range of algae-pyrolysis related topics, including advanced-pyrolysis techniques and the potential biochar applications in soil amendment, energy storage, catalysts, chemical industries, and wastewater-treatment plants.

Efficacy and cytotoxicity of engineered ferromanganese-bearing sludge-derived biochar for percarbonate-induced phthalate ester degradation

Phthalate esters (PAEs) are a group of ubiquitous organic environmental contaminants. Engineered ferromanganese-bearing sludge-derived biochar (SDB), synthesized using one-step pyrolysis in the temperature range between 300 and 900 °C, was used to enable Fenton-like processes that decontaminated PAE-laden sediments. SDB was thoroughly characterized using scanning electron microscopyenergy-dispersive spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller surface area, thermogravimetric analysis, Raman spectroscopy, Fourier-transform infrared spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis. The maximum PAE degradation was remarkable at 90% in 12 h at pH 6.0 in the presence of 1.7 g L^-1 of SDB 900. The highly-effective PAE degradation was mainly attributed to the synergism between FeO_x and MnO_x, which strengthened the activation of percarbonate (PC) via electron transfer, hydroxy addition, and hydrogen abstraction through radical (HO•) and nonradical (¹O₂) oxidation mechanisms, thereby facilitating PAE catalytic degradation over SDB in real sediments, which clearly proved the efficacy of ferromanganese-bearing SDB and PC for the remediation of contaminated sediments. The cytotoxicity exhibited by human skin keratinocyte cells exposure to high SDB concentration (100-400 µg mL^-1) for 24-48 h was low indicating insignificant cellular toxicity and oxidative damages. This study provides a new strategy for freshwater sludge treatment and reutilization, which enables a water-cycle-based circular economy and waste-to-resource recycling.

Biochar based photocatalyst for degradation of organic aqueous waste: A review

The advancement in the treatment technology for wastewater containing recalcitrant pollutants to lower the overall cost and time of the treatment processes is the prime demand. Biochar (BC) based photocatalyst have proved their potential application in the photo-degradation of a wide range of organic pollutants. The structural and chemical properties of the BC enhance the efficacy of photocatalyst, improving its optical properties with increased stability. This review gives an overview of the progress that occurred during the last five years in BC-based photocatalyst for degradation of recalcitrant organic waste in the aqueous system, emphasizing the role of BC in the photocatalytic performance with a brief discussion regarding the various sources of BC and different strategies used to modify the BC. Further, the critical challenges are discussed, which would be confronted during the scaling up and real-time application in wastewater treatment.

Peroxymonosulfate activation by a metal-free biochar for sulfonamide antibiotic removal in water and associated bacterial community composition

Antibiotic sulfamethoxazole (SMX) has been commonly found in various water matrices, therefore effective decontamination method is urgently needed. Metal-free pristine coconut-shell-derived biochar (CSBC), synthesized by thermochemical conversion at 700 °C, was used for activating peroxymonosulfate (PMS), an oxidant, to degrade SMX, a sulfonamide antibiotic, in water. SMX degradation, maximized at 0.05 mM concentration, was 85% in 30 min at pH 5.0 in the presence of 150 mg L^-1 of CSBC. Remarkably, SMX removal reached 99% in a chloride-rich CSBC/PMS system. SMX degradation was mainly attributed to the role of CSBC in enhancing PMS activation to produce combined radical (SO₄^•-/HO•) and nonradical (¹O₂) reaction pathways. The most abundant genus in the CSBC/PMS system was Methylotenera, which belonged to the Proteobacteria phylum. Thus, from a perspective of biowaste-to-resource recycling and circular bioeconomy view point, CSBC is a potential catalytic activator of PMS for the removal of sulfonamide antibiotics from aqueous environments.

Remediation of contaminated dredged harbor sediments by combining hydrodynamic cavitation, hydrocyclone, and persulfate oxidation process

A pilot-scale hybrid treatment system consisting of hydrodynamic cavitation (HC), hydrocyclone separator (HS), and sodium persulfate (PS), was employed for removing polycyclic aromatic hydrocarbons (PAHs) from dredged harbor sediments. The effectiveness of PAH degradation was studied by varying the inlet pressure (0-2.0 bar), PS dosage (or Σ[PAH] to [PS] mole ratio of 1:1-1:10³) at HS inflow velocity of 2.85 m/s, slurry concentration of 10%, and reaction time of 60 min. The degradation rate of PAH in the overflow (OF) sediment was significantly lower than that of the underflow (UF) sediment. After an inlet pressure increase of 0.5 bar and ΣPAH: [PS] molar ratio of 1: 10, the PAH removal was 87% and 55% in the UF and OF, respectively, by the combined HC-PS-HS unit. Without PS, the PAHs removal was 46% and 40% in the UF and OF, respectively. The removal efficiency for 6-, 5-, 4-, 3-, and 2-ring PAHs was 100%, 93%, 93%, 92%, and 82% in the UF and 55%, 61%, 67%, 47%, and 36% in the OF by the combined HC-PS-HS system. FEEM spectroscopy clarified that aromatic protein-based components (tryptophan- and tyrosine-like combined) were gradually degraded and transformed into soluble microbial metabolites when organic matter content declined during the combined HC-PS-HS treatment. This study provides new insights into the combined HC-PS-HS system for PAH degradation in dredged sediments.

Hydrodynamic cavitation activation of persulfate for the degradation of polycyclic aromatic hydrocarbons in marine sediments

Hydrodynamic cavitation (HC) coupled with persulfate (PS)-based that resulted in the synergistic degradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated marine sediments. The effects of HC injection pressure and Σ[PAH]: [PS] on the rate and extent of PAH degradation were studied in the pressure range of 0.5-2.0 bar, PS concentration rage of 2 × 10^-4 to 2 × 10^-2 M or Σ[PAH]: [PS] of 1:10-1000, and reaction time of 20-60 min. A pseudo-first-order rate law fitted PAHs removal kinetics well. The degradation rate constant increased with injection pressure, reaching the maximum level at 0.5 bar, then decreased at injection pressure became greater than 0.5 bar. The results showed that PAH removal was 84% by the combined HC and PS process, whereas, HC alone only achieved a 43% removal of PAHs in marine sediments under the optimal inlet pressure of 0.5 bar at PS concentration of 2 × 10^-2 M in 60 min. The HC‒PS system effectively removed PH, PY, FLU, BaA, and CH at 91, 99, 91, 84, and 90%, respectively. The maximum removal of 6-, 5-, 4-, 3-, and 2-ring PAHs was 89, 87, 84, 76, and 34%, respectively. Major reactive oxygen species (ROSs), namely, SO₄^-• and HO•, were responsible for PAHs degradation. Results clearly highlighted the feasibility of HC-PS system for the clean-up of PAHs-laden sediments in particular and other recalcitrant organic contaminants in general.

Efficient degradation of sulfamethazine via activation of percarbonate by chalcopyrite

In this work, the novel application of chalcopyrite (CuFeS₂) for sodium percarbonate (SPC) activation towards sulfamethazine (SMT) degradation was explored. Several key influencing factors like SPC concentration, CuFeS₂ dosage, reaction temperature, pH value, anions, and humic acid (HA) were investigated. Experimental results indicated that SMT could be effectively degraded in the neutral reaction media by CuFeS₂/SPC process (86.4%, 0.054 min^-1 at pH = 7.1). The mechanism of SPC activation by CuFeS₂ was elucidated, which was discovered to be a multiple reactive oxygen species (multi-ROS) process with the coexistence of hydroxyl radical (^•OH), carbonate radical (CO₃^•-), superoxide radical (O₂^•-), and singlet oxygen (¹O₂), as evidenced by quenching experiments and electron spin resonance (ESR) tests. The generated ^•OH via the traditional heterogeneous Fenton-like process would not only react with carbonate ions to yield other ROS but also involve in SMT degradation. The abundant surface-bound Fe(II) was deemed to be the dominant catalytic active sites for SPC activation. Meanwhile, it was verified that the reductive sulfur species, the interaction between Cu(I) and Fe(III) as well as the available O₂^•- derived from the activation of molecular oxygen and the conversion of ^•OH favored the regeneration of Fe(II) on CuFeS₂ surface. Furthermore, the degradation intermediates of SMT and their toxicities were evaluated. This study presents a novel strategy by integrating transition metal sulfides with percarbonate for antibiotic-contaminated water treatment.

Bacteria, Fungi and Microalgae for the Bioremediation of Marine Sediments Contaminated by Petroleum Hydrocarbons in the Omics Era

Petroleum hydrocarbons (PHCs) are one of the most widespread and heterogeneous organic contaminants affecting marine ecosystems. The contamination of marine sediments or coastal areas by PHCs represents a major threat for the ecosystem and human health, calling for urgent, effective, and sustainable remediation solutions. Aside from some physical and chemical treatments that have been established over the years for marine sediment reclamation, bioremediation approaches based on the use of microorganisms are gaining increasing attention for their eco-compatibility, and lower costs. In this work, we review current knowledge concerning the bioremediation of PHCs in marine systems, presenting a synthesis of the most effective microbial taxa (i.e., bacteria, fungi, and microalgae) identified so far for hydrocarbon removal. We also discuss the challenges offered by innovative molecular approaches for the design of effective reclamation strategies based on these three microbial components of marine sediments contaminated by hydrocarbons.

Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate (SPC) and peroxymonocarbonate (PMC) have been widely used in modified Fenton reactions because of their multiple superior features, such as a wide pH range and environmental friendliness. This broad review is intended to provide the fundamental information, status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades. Both SPC and PMC can directly decompose various pollutants. The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC. The most commonly used catalysts for SPC activation are iron compounds while cobalt compositions are applied to activate PMC in homogenous and heterogeneous catalytical systems. The generation and participation of hydroxyl, superoxide and/or carbonate radicals are involved in the activated SPC and PMC system. The reductive radicals, such as carbon dioxide and hydroxyethyl radicals, can be generated when formic acid or methanol is added in the Fe(II)/SPC system, which can reduce target contaminants. SPC can also be activated by energy, tetraacetylethylenediamine, ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition. The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment. The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.

The Role of Biochar in Regulating the Carbon, Phosphorus, and Nitrogen Cycles Exemplified by Soil Systems

Biochar is a carbon-rich material prepared from the pyrolysis of biomass under various conditions. Recently, biochar drew great attention due to its promising potential in climate change mitigation, soil amendment, and environmental control. Obviously, biochar can be a beneficial soil amendment in several ways including preventing nutrients loss due to leaching, increasing N and P mineralization, and enabling the microbial mediation of N2O and CO2 emissions. However, there are also conflicting reports on biochar effects, such as water logging and weathering induced change of surface properties that ultimately affects microbial growth and soil fertility. Despite the voluminous reports on soil and biochar properties, few studies have systematically addressed the effects of biochar on the sequestration of carbon, nitrogen, and phosphorus in soils. Information on microbially-mediated transformation of carbon (C), nitrogen (N), and phosphorus (P) species in the soil environment remains relatively uncertain. A systematic documentation of how biochar influences the fate and transport of carbon, phosphorus, and nitrogen in soil is crucial to promoting biochar applications toward environmental sustainability. This report first provides an overview on the adsorption of carbon, phosphorus, and nitrogen species on biochar, particularly in soil systems. Then, the biochar-mediated transformation of organic species, and the transport of carbon, nitrogen, and phosphorus in soil systems are discussed. This review also reports on the weathering process of biochar and implications in the soil environment. Lastly, the current knowledge gaps and priority research directions for the biochar-amended systems in the future are assessed. This review focuses on literatures published in the past decade (2009–2021) on the adsorption, degradation, transport, weathering, and transformation of C, N, and P species in soil systems with respect to biochar applications.

Capacity and potential mechanisms of Cd(II) adsorption from aqueous solution by blue algae-derived biochars

The removal of potentially toxic metals by biochars is currently a popular and salutary method. In this study, we combined the advantages of blue algae (Microcystic) and pyrolysis technology to produce a late-model biochar. Moreover, the adsorption capacity and potential mechanisms of blue algae-derived biochars for the removal of cadmium (Cd) from aqueous solution were evaluated in comparison with the adsorption capacity and potential mechanisms of corn straw-derived biochar (CSBC) and rice husk-derived biochar (RHBC). Batch adsorption experiments were used to explore the adsorption performance of biochars, and a wide range of characterization techniques were employed: scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and zeta potential analysis. The results showed that the adsorption isotherms could be described well by the Langmuir model and that the pseudo-second-order model fit the Cd(II) adsorption kinetics best, indicating that the process was monolayer and controlled by chemisorption. Moreover, the Cd(II) removal capacity of optimal blue algae-derived biochar (BC600-2) (135.7 mg g^-1) was 85.9% and 66.9% higher than the removal capacity of CSBC and RHBC, respectively. In addition, the results of the characterization methods showed that precipitation with minerals was the primary mechanism, accounting for 68.7-89.5% of the capacity. Overall, blue algae-derived biochars, as a product from freshwater biowaste, may be a novel and potentially valuable adsorbent for Cd(II) removal.

Application of biochar for the remediation of polluted sediments

Polluted sediments pose potential threats to environmental and human health and challenges to water management. Biochar is a carbon-rich material produced through pyrolysis of biomass waste, which performs well in soil amendment, climate improvement, and water treatment. Unlike soil and aqueous solutions, sediments are both the sink and source of water pollutants. Regarding in-situ sediment remediation, biochar also shows unique advantages in removing or immobilizing inorganic and organic pollutants (OPs). This paper provides a comprehensive review of the current methods of in-situ biochar amendments specific to polluted sediments. Physicochemical properties (pore structure, surface functional groups, pH and surface charge, mineral components) were influenced by the pyrolysis conditions, feedstock types, and modification of biochar. Furthermore, the remediation mechanisms and efficiency of pollutants (heavy metals [HMs] and OPs) vary with the biochar properties. Biochar influences microbial compositions and benthic organisms in sediments. Depending on the location or flow rate of polluted sediments, potential utilization methods of biochar alone or coupled with other materials are discussed. Finally, future practical challenges of biochar as a sediment amendment are addressed. This review provides an overview and outlook for sediment remediation using biochar, which will be valuable for further scientific research and engineering applications.

Application of macroalgal biomass derived biochar and bioelectrochemical system with Shewanella for the adsorptive removal and biodegradation of toxic azo dye

The present study aimed towards adsorptive removal of the toxic azo dye onto biochar derived from Eucheuma spinosum biomass. Characterization of the produced biochar was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). Eucheuma spinosum biochar (ES-BC) produced at 600 °C revealed a maximum adsorption capacity of 331.97 mg/g towards reactive red 120 dye. The adsorption data fitted best to the pseudo-second order kinetics (R² > 0.99) and Langmuir isotherm (R² > 0.98) models. These adsorption models signified the chemisorption mechanism with monolayer coverage of the adsorbent surface with dye molecules. Furthermore, the adsorption process was mainly governed by electrostatic interaction, ion exchange, metal complexation, and hydrogen bonding as supported by the solution pH, FTIR, XPS, and XRD investigation. Nevertheless, alone adsorption technology could not offer a complete solution for eliminating the noxious dyes. Therefore, the bioelectrochemical system (BES) equipped with previously isolated marine Shewanella marisflavi BBL25 was intended for the complete remediation of azo dye. The BES II demonstrated highest dye decolorization (97.06%) within 48 h at biocathode where the reductive cleavage of the azo bond occurred. Cyclic voltammetry (CV) studies of the BES revealed perfect redox reactions taking place where the redox mediators shuttled the electrons to the dye molecule to accelerate the dye decolorization. Besides, the GC-MS analysis revealed biotransformation of the dye into less toxic metabolites as tested using a phyto and cytogenotoxicity.

Effects of biochar on catalysis treatment of 4-nonylphenol in estuarine sediment and associated microbial community structure

The effect of pyrolysis temperature on the generation of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge biochar (SSB) and the removal of hazardous chemicals from esturine sediments by SSB and sodium percarbonate (SPC), exemplified by 4-nonylphenol (4-NP) were studied. SSB synthesized at 500 °C (SSB500) achieved the highest 4-NP degradation efficiency of 73%, at pH₀ 9.0 in 12 h of reaction time. The enhanced 4-NP degradation was attributed to the SSB500 activation activation of SPC that produced sufficient •OH and CO₃^-• due to electron-transfer interaction on the Fe-Mn redox pairs. The microbial community diversity and composition of the treated sediment were compared using high-throughput sequencing. Results showed SSB/SPC treatment increased the microbial diversity and richness in the sediments. Proteobacteria were the keystone phylum, while Thioalkalispira genera were responsible for 4-NP degradation in the SSB/SPC treatment. Over all, results revealed the change in the bacterial community during the environmental applications of SSB, which provided essential information for better understanding of the monitoring and improvement of sustainable sediment ecosystems.

Activation of percarbonate by water treatment sludge-derived biochar for the remediation of PAH-contaminated sediments

Sludge from a groundwater treatment plant was used to prepare biochar by pyrolysis. The Fe-Mn rich biochar was used to activate percarbonate for the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated aquatic sediments. Results showed that the sludge-derived biochar (SBC) produced at a pyrolysis temperature of 700 °C was the most effective in activating percarbonate, which exhibited significant oxidative removal of PAHs. PAHs degradation took place via a Fenton-like oxidation manners, contributed from the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox pairs, and achieved the highest degradation efficiency of 87% at pH₀ 6.0. Reactions between oxygenated functional groups of biochar and H₂O₂ generated of O₂^•- and HO• radicals in abundance under neutral and alkaline pH was responsible for the catalytic degradation of PAHs. Our results provided new insights into the environmental applications of SBC for the green sustainable remediation of organics-contaminated sediments and aided in reduction of associated environmental and health risk.