A critical review of the production and advanced utilization of biochar via selective pyrolysis of lignocellulosic biomass

Current Challenges and Perspectives for the Catalytic Pyrolysis of Lignocellulosic Biomass to High-Value Products

Lignocellulosic biomass is an excellent alternative of fossil source because it is low-cost, plentiful and environmentally friendly, and it can be transformed into biogas, bio-oil and biochar through pyrolysis; thereby, the three types of pyrolytic products can be upgraded or improved to satisfy the standard of biofuel, chemicals and energy materials for industries. The bio-oil derived from direct pyrolysis shows some disadvantages: high contents of oxygenates, water and acids, easy-aging and so forth, which restrict the large-scale application and commercialization of bio-oil. Catalytic pyrolysis favors the refinement of bio-oil through deoxygenation, cracking, decarboxylation, decarbonylation reactions and so on, which could occur on the specified reaction sites. Therefore, the catalytic pyrolysis of lignocellulosic biomass is a promising approach for the production of high quality and renewable biofuels. This review gives information about the factors which might determine the catalytic pyrolysis output, including the properties of biomass, operational parameters of catalytic pyrolysis and different types of pyrolysis equipment. Catalysts used in recent research studies aiming to explore the catalytic pyrolysis conversion of biomass to high quality bio-oil or chemicals are discussed, and the current challenges and future perspectives for biomass catalytic pyrolysis are highlighted for further comprehension.

Effect of biochar amendment on metal mobility, phytotoxicity, soil enzymes, and metal-uptakes by wheat (Triticum aestivum) in contaminated soils

The use of low-cost substances such as biochar could be a sustainable approach to reduce the mobility, accumulation, and toxic impact of heavy metals in crop systems. This study investigates the effect of biochar amendment on heavy metal (Cr, Cd, Cu, Pb, Ni, Zn, Mg and Fe) mobility, bioaccumulation factor (BAF), plant (wheat) metal-uptake, plant oxidative stress, and soil enzymatic profile in contaminated industrial soil. Biochar was obtained from slow pyrolysis of Lantana (LBC), and Parthenium (PBC) biomass, and applied at 3% rates in contaminated soils for wheat crop study under a greenhouse experimental setup. Results show in comparison with control setups, low mobility of Cr (14.15-16.35%), Cd (7.17-15.24%), Cu (9.81-12.97%), Pb (7.99-15.23%), Ni (1.52-2.38%), Zn (10.47-14.42%), Mg (48.85-52.89%), and Fe (19.13-19.90%) contents in soils. The heavy metal uptake rates were 63.08% (Cr), 78.07% (Cd), 74.61% (Cu), 78.11% (Pb), 75.73% (Ni), 69.71% (Zn), 28.78% (Mg), and 49.26% (Fe) lower in biochar amendments, compared with the control treatments. Similarly, the biochar amended treatments exhibited low oxidative stress in wheat plants than control setups. In addition, soil enzymes (dehydrogenase, β-glucosidase, alkaline phosphatase, and urease) alleviated in biochar amended soils indicating reduced toxicity of metals in experimental soils. In summary, this study indicates that biochar amendment in contaminated soils not only improves plant growth but also lowers the rates of soil and plant toxicity and metal bioavailability as well.

Synthesis of carbon molecular sieves from agricultural residues: Status, challenges and prospects

Adsorption is the most promising technology used in the gas separation and purification process. The key success of this technology relies on the selection of an adsorbent. Activated carbon and zeolites are the most commonly used adsorbents in the separation of particular gas from gaseous mixtures. Activated carbon deriving from fossil and biomass-based resources has wide pore size distribution and thereby results in lower selectivity. Whereas, zeolites synthesized from natural minerals are expensive which increases the cost of the purification process. Taking this into concern, the quest for synthesizing low-cost and effective adsorbents has gained greater attention in recent years. Carbon Molecular Sieves (CMSs), are considered as an attractive alternative to replace the conventional adsorbents. Furthermore, CMSs exhibit higher selectivity and adsorption capacity, due to their narrow micropore size distribution (0.3-0.5 nm). CMSs are synthesized from any organic carbonaceous precursor with low inorganic content. Since most of the agricultural residues fall under this category, they can be used as a feedstock for CMSs production. The synthesis of CMSs involves three stages: carbonization, activation, and pore modification. In this review, physicochemical characteristics of various agricultural residues, the effects of carbonization process parameters, activation methods, and pore modification techniques adopted for producing CMSs are comprehensively discussed. The effect of deposition temperature, time, and flow rate of depositing agent on pore characteristics of CMSs is briefed. The prospects and challenges in CMSs production are also studied. The insights in this review provide guidelines for synthesizing CMSs from agro-residues.

Valorization of agriculture waste biomass as biochar: As first-rate biosorbent for remediation of contaminated soil

Each year, Asia produces an estimated 350 million tonnes of agricultural residues. According to Ministry of Power projections, numerous tonnes of such waste are discarded each year, in addition to being used as green manure. The methodology used to convert agricultural waste into the most valuable biochar, as well as its critical physical and chemical properties, were described in this review. This review also investigates the beneficial effects of bio and phytoremediation on metal(lloid)-contaminated soil. Agriculture biomass-based biochar is an intriguing organic residue material with the potential to be used as a responsible solution for metal(lloid) polluted soil remediation and soil improvement. Plants with faster growth and higher biomass can meet massive remediation demands. Recent research shows significant progress in agricultural biomass-based biomass conversion as biochar, as well as understanding the frameworks of metal(lloid) accumulation and mobility in plants used for metal(lloid) polluted soil remediation. Biochar made from various agricultural biomass can promote native plant growth and improve phytoremediation efficiency in polluted soil with metal(lloid)s. This carbon-enriched biochar promotes native microbial activity by neutralising pH and providing adequate nutrition. Thus, this review critically examines the feasibility of converting agricultural waste biomass into biochar, as well as the impact on plant and microbe remediation potential in metal(lloid)s polluted soil.

Collagen Fiber-Based Advanced Separation Materials: Recent Developments and Future Perspectives

Separation plays a critical role in a broad range of industrial applications. Developing advanced separation materials is of great significance for the future development of separation technology. Collagen fibers (CFs), the typical structural proteins, exhibit unique structural hierarchy, amphiphilic wettability, and versatile chemical reactivity. These distinctive properties provide infinite possibilities for the rational design of advanced separation materials. During the past 2 decades, many progressive achievements in the development of CFs-derived advanced separation materials have been witnessed already. Herein, the CFs-based separation materials are focused on and the recent progresses in this topic are reviewed. CFs widely existing in animal skins display unique hierarchically fibrous structure, amphiphilicity-enabled surface wetting behaviors, multi-functionality guaranteed covalent/non-covalent reaction versatility. These outstanding merits of CFs bring great opportunities for realizing rational design of a variety of advanced separation materials that were capable of achieving high-performance separations to diverse specific targets, including oily pollutants, natural products, metal ions, anionic contaminants and proteins, etc. Besides, the important issues for the further development of CFs-based advanced separation materials are also discussed.

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.

Resource utilization of agricultural waste: Converting peanut shell into an efficient catalyst in persulfate activation for degradation of organic pollutant

Agricultural waste was characterized by large quantity and low degree of resource utilization. The peanut shell waste was converted into value-added biochar to alleviate the pollution of dyeing wastewater, which caters to the concept of resource recovery and sustainable utilization. In this work, peroxydisulfate (PDS) could be efficiently activated by biochar obtained by pyrolysis at 700 °C (BC) and Acid Orange 7 (AO7) was rapidly eliminated with 96% removal ratio in 10 min. Meanwhile, BC catalyst performed good stability and reusability. In addition, remarkable removal performance within 40 min (>94%) could be achieved in a wide range of pH (3.0-11.0). Through series characterizations, it was found that 700 °C was the critical pyrolysis temperature to prepare material with excellent property mainly attributing to large specific surface area (SSA), followed by high defect structure and rich C-O. It was speculated that radical pathway mainly especially surface-bounded radicals (SO₄^•-、•OH、O₂^-•) worked in the degradation of AO7. Specifically, abundant and typical oxygen-containing functional groups (OFGs) and defect structure catalytic sites of BC enhanced PDS activation. In addition, various radicals participated the whole degradation processes, such as the cleavage of azo bond (-NN-), hydroxylation, deamination and desulfurization.

How Biochar Derived from Pond Cypress (Taxodium Ascendens) Evolved with Pyrolysis Temperature and Time and Their End Efficacy Evaluation

Biomass type, pyrolysis temperature, and duration can affect biochar properties simultaneously. To further clarify the mechanism of this interaction, the branch and leaf parts of Pond cypress (Taxodium ascendens) were separately pyrolyzed at four peak temperatures (350 °C, 450 °C, 650 °C, and 750 °C) for three different durations (0.5 h, 1 h, and 2 h) in this study. The resulting biochar properties were measured, which included the yield, specific surface area (SSA), pH, EC (electricity conductivity), the bulk and surface elemental composition, and the contents of moisture, ash, fixed carbon, and volatile matter. The results showed that the pyrolysis temperature was more determinant for the modification of all biochar, but the residence time had a significant effect on the yield, pH, and SSA of branch-based biochar (B-biochar) at specific temperatures. However, such a phenomenon only happened on the pH of leaf-based biochar (L-biochar). Results: (1) With the temperature at 350 and 650 °C, the residence time had a significant effect on the yield of B-biochar. (2) The pH of B-biochar and L-biochar varied considerably between durations when the heating temperature hit 650 and 750 °C. (3) The SSA of B-biochar possessed an obvious fluctuation with the time during the pyrolysis from 650 to 750 °C. According to the properties measured above, the principal component and the cluster analysis classified the 24 types of biochar made in this experiment into four groups and revealed that an obvious disparity existed between B-biochar and L-biochar that were pyrolyzed at temperatures ranging from 450 to 750 °C, which suggested that biomass type was the primary factor for biochar-making. All this information can provide valuable references for the optimization of biochar-making in the real world.

Preparation of high-value porous carbon by microwave treatment of chili straw pyrolysis residue

Microwave technology is utilized to prepare porous carbon from the chili straw pyrolysis residue in this study. As the pyrolysis temperature increases, the thermal stability of biochar is higher. The carbon speciation of the porous carbon PC500 is closest to that of graphite, and its inorganic-C reaches to 51.21%. Notably, the specific surface area of the activated porous carbon increases with increasing pyrolysis temperature, with a maximum value of 2768.52 m²/g for PC500. Further testing of the electrochemical properties of the porous carbon, PC500 possesses a high specific capacitance of 352F/g at 1 A/g while that of conventional heating is only 226.1F/g. The porous carbon prepared by microwave heating has better electrical properties compared to conventional heating, and the biochar obtained at higher pyrolysis temperature has a richer pore structure after activation.

Synthesis of nitrogen-enriched hydrochar via co-hydrothermal reaction of liquid digestate and corn stalk

Synthesis of carbon material from low-cost and sustainable precursors has been intensively explored in recent years. In this study, a nitrogen (N)-enriched hydrochar was developed via a facile one-step hydrothermal carbonization (HTC) of corn stalk (CS) with liquid digestate (LD) of food waste. The LD substituted water and functioned as the N precursor during HTC. The physicochemical properties of hydrochar derived at different HTC temperatures (180-300 °C) were examined and the reaction mechanism was investigated. Intermolecular dehydration and condensation were the primary reactions in the HTC process of CS without LD. The CS-chars maintained the original structure and morphology of the raw corn stalk. The ammonia and inorganic salts in LD promoted the lignin removal, and accelerated the cleavage of the glycosidic linkages of the polysaccharide and hydrogen bonds of cellulose. Benefited from the ammonia and metals in the LD, the recalcitrance structure of the corn stalk was disrupted during the co-HTC even at a low temperature of 220 °C. Moreover, carbon spheres were observed in the LDCS-chars, indicating the LDCS-chars were resulted from sequential hydrolysis, dehydration and condensation during co-HTC reactions. Reactions between N compounds in the LD and derivatives from CS contributed to N doping. The N content of LDCS-chars achieved 4.95% at 260 °C and 83.94% of the N was presented as pyridinic-N. Co-hydrothermal treatment of CS and LD not only enhanced the characteristics of hydrochar, but also recovered two-thirds of ammoniacal N from the digestate to reduce greenhouse gas emission.

Energy-efficient biochar production for thermal backfill applications

The function of engineered thermal backfills surrounding underground pipelines of the crude oil industry is to prohibit heat migration for the design period of 25 to 50 years. Biochar is suitable for reconstituting standard thermal backfill material since it is biochemically inert and has a low heat conductivity. However, the preparation of biochar from biomass involves an energy-intensive pyrolysis process. This study aims to make biochar production energy-efficient via optimizing the pyrolysis temperatures, specifically for thermal backfill applications. Ten distinct biochars were prepared by pyrolyzing two waste biomass, i.e., water hyacinth (WH) and sugarcane bagasse (SB), at temperatures ranging from 300 to 700 °C. The biochars were assessed based on their thermal conductivity, energy consumption, yield, and stability in soil for the design period. The thermal conductivity of produced biochars varied in a narrow range of 0.10 to 0.13 W m^-1 K^-1 with different pyrolysis temperatures, which is possibly due to marginal differences in their microstructure, mineralogy, and physicochemical properties. The findings revealed that the biochar produced at lowest pyrolysis temperature (300 °C) consumed least energy and produced maximum yield. However, it was not suitable for thermal backfill applications due to its inadequate carbon stability in soil. Therefore, the current study recommends a pyrolysis temperature of 400 °C for thermal backfill applications. The recommended pyrolysis temperature was found to be at least 60% energy efficient in comparison to pyrolysis at 700 °C for both the feedstocks. This study provides crucial insight into the role of pyrolysis temperature for tailoring biochar production for intended applications.

Environmental remediation by tea waste and its derivative products: A review on present status and technological advancements

The rising consumption of the popular non-alcoholic beverage tea and its derivative products caused massive growth in worldwide tea production in the last decade, leading to the generation of huge quantities of waste tea residues every year. Most of these wastes are usually burnt or disposed in landfills without proper treatment which results in serious environmental issues by polluting water, air and soil. In the recent times, 'waste to wealth' is a fast-growing concept for environment friendly sustainable development. Utilization of the large amount of tea wastes for the production of low-cost adsorbents to reduce the expenses of water and wastewater treatment can be a sustainable way of management of these wastes which at the same time will improve circular economy also. This review endeavours to evaluate the potential of both raw and modified tea wastes towards the adsorption of pollutants from wastewater. The production of various adsorptive materials such as biochar, activated carbon, nanocomposites, hydrogels, nanoparticles from tea wastes are summarized. The advancements in their applications for the removal of different emerging contaminants from wastewater as well as potable water, air and soil are exhaustively reviewed. The outcome of the present review reveals that tea waste and its derivatives are appropriate candidates to be used as adsorbents that show tremendous effectiveness in cleaning the environment. This article will provide the readers with an in-depth knowledge on the sustainable utilization of tea waste as adsorbent materials and will assist them to explore this abundant cheap waste biomass for environmental remediation.

Iron-biochar production from oily sludge pyrolysis and its application for organic dyes removal

In this study, a single-step pyrolysis approach was developed to directly convert oily sludge (OS) with high iron content into a magnetic iron-char catalyst for organic dyes removal. Magnetic iron-char catalysts were employed to degrade crystal violet (CV), methylene blue (MB), and sunset yellow (SY). The OC800 iron-char catalyst prepared from OS was not only rich in iron (mainly stable Fe₃O₄), but also showed favorable pore structures. Effects of operation parameters like temperature, H₂O₂ dosage, and pH on dye removal based on Fenton degradation were examined. In OC800 Fenton system (0.5 mL H₂O₂, 500 mg/L dye concentration, and pH = 2 in 50 mL solution), the maximum dye removal capacities of SY, CV, and MB were 83.61, 639.19, and 414.25 mg/g, respectively. In dyes degradation experiments, the prepared catalyst could be reused (more than 3 successive cycles) due to higher stability and less leaching of iron. One-step pyrolysis of OS with high iron content thereby represents a promising approach to transform sludge waste to functional biochar that removes hazardous dyes.

Electricity Generation from Municipal Solid Waste in Nigeria: A Prospective LCA Study

Diverse opportunities and environmental impacts could occur from a potential move towards waste-to-energy (WtE) systems for electricity generation from municipal solid waste (MSW) in Lagos and Abuja, Nigeria. Given this, the purpose of this study is to use life cycle assessment (LCA) as a primary analytical approach in order to undertake a comparative analysis from an environmental impact perspective of different WtE scenarios, along with diesel backup generators (DBGs) and grid electricity. A functional unit of 1 kilowatt-hour of electricity produced was used in assessing the following environmental impact categories: abiotic depletion (fossil fuels) potential (ADP), global warming potential (GWP 100a), human toxicity potential (HTP), photochemical oxidation potential (POCP), acidification potential (AP), and eutrophication potential (EP). The overall result indicated that anaerobic digestion (AD) had the highest energy generated per one tonne of MSW processed for both Lagos (683 kWh/t) and Abuja (667 kWh/t), while landfill gas to energy (LFGTE) had the lowest for both (Lagos 171 kWh/t, Abuja 135 kWh/t). AD also had the lowest environmental impacts amongst the four WtE systems for both cities based on all the impact categories except for POCP. In contrast, LFGTE had the highest impact in all the categories except ADP and HTP. Extending the analysis to include diesel-based generators (DBG) and grid electricity saw the DBGs having the highest impact overall in ADP (14.1 MJ), HTP (0.0732 Kg, 1.4 DB eq), AP (0.0129 Kg SO2 eq), and EP (0.00313 Kg PO4 eq) and grid electricity having the lowest impact in GWP (0.497 Kg CO2 eq), AP (0.000296 Kg SO2 eq), and EP (0.000061 Kg PO4 eq). It was concluded that additional electricity supply from AD to the grid, with its potential to reduce the reliance on DBGs (worst scenario overall), would be a positive action in environmental impact terms.

Biochar: Production, Applications, and Market Prospects in Portugal

Biochar produced during the thermochemical decomposition of biomass is an environmentally friendly replacement for different carbon materials and can be used for carbon sequestration to mitigate climate change. In this paper, current biochar production processes and top market applications are reviewed, as well as emerging biochar uses gaining momentum in the market. Various application fields of biochar, including agricultural applications (e.g., soil conditioning), adsorption (for soil and water pollutants), carbon sequestration, catalysis, or incorporation into composites or construction materials, are also presented and discussed. According to this literature overview, slow pyrolysis is the preferred process for biochar production, whereas agricultural applications (for soil conditioning and fertilization) are the most studied and market-ready solutions for biochar use. The Alentejo region (Portugal) shows tremendous potential to be a major player in the developing biochar market considering feedstock availability and large areas for biochar agricultural application. Biochar’s production potential and possible benefits were also estimated for this Portuguese region, proving that agricultural application can effectively lead to many environmental, economic, and social gains.

A Weed-Derived Hierarchical Porous Carbon with a Large Specific Surface Area for Efficient Dye and Antibiotic Removal

Adsorption is an economical and efficient method for wastewater treatment, and its advantages are closely related to adsorbents. Herein, the Abutilon theophrasti medicus calyx (AC) was used as the precursor for producing the porous carbon adsorbent (PCAC). PCAC was prepared through carbonization and chemical activation. The product activated by potassium hydroxide exhibited a larger specific surface area, more mesopores, and a higher adsorption capacity than the product activated by sodium hydroxide. PCAC was used for adsorbing rhodamine B (RhB) and chloramphenicol (CAP) from water. Three adsorption kinetic models (the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models), four adsorption isotherm models (the Langmuir, Freundlich, Sips, and Redlich–Peterson models), and thermodynamic equations were used to investigate adsorption processes. The pseudo-second kinetic and Sips isotherm models fit the experimental data well. The adsorption mechanism and the reusability of PCAC were also investigated. PCAC exhibited a large specific surface area. The maximum adsorption capacities (1883.3 mg g⁻¹ for RhB and 1375.3 mg g⁻¹ for CAP) of PCAC are higher than most adsorbents. Additionally, in the fixed bed experiments, PCAC exhibited good performance for the removal of RhB. These results indicated that PCAC was an adsorbent with the advantages of low-cost, a large specific surface area, and high performance.

Nickel-loaded shrimp shell biochar enhances batch anaerobic digestion of food waste

This study evaluated the effectiveness of shrimp shell biochar (SBC) and nickel (Ni) loaded SBC in increasing methane yield during anaerobic digestion of food waste. The results indicated that the methane yields of control (without SBC), SBC, SBC loaded with the low concentration of Ni, and SBC loaded with the high concentration of Ni were 81.8, 116.1, 134.7, and 99.2 mL/(g·VS), respectively. SBC promoted the efficiency and stability of the whole anaerobic digestion process including hydrolysis, volatile fatty acid conversion and methanogenesis. While the invigorating effect of loaded Ni at the low concentration of 0.88 mg/g was mainly concentrated in methanogenesis, the inhibition effect of the high Ni concentration was comprehensive. SBC helped Methanosarcina proliferation, and low concentration Ni promoted the number and activity of Methanosarcina and Methanosaeta. The results show that biochar loaded with a low level of trace elements such as Ni can promote the anaerobic digestion process.

Stabilization of heavy metals in biochar derived from plants in antimony mining area and its environmental implications

Heavy metals pollution in mining soils seriously threatens the ecological environment and human health worldwide. Phytoremediation is considered to be an ideal method to reduce the toxicity, mobility, and bioavailability of heavy metals in the soils. However, the disposal of plant-enriched heavy metals has become a thorny problem. To estimate the effect of pyrolysis on the stabilization of heavy metals in post-phytoremediation plant residues, different biochars were prepared from Conyza canadensis (CC), Gahnia tristis (GT), and Betula luminifera (BL) at different pyrolysis temperatures (300, 450, and 600 °C). Results indicated that pyrolysis was effective in the stabilization of heavy metals (Cr, Ni, As, Sb, Hg, and Pb) in plants and significantly (P < 0.05) decreased the bioavailability of most heavy metals. Among them, GT₆₀₀ prepared by pyrolysis of GT at 600 °C has the best stabilization effect on Sb, which increases the residual fraction by 7.32 times, up to 82.05%. The results of environmental risk assessment show that pyrolysis of biomass at high temperature (600 °C) can effectively mitigate the environmental impact of As, Sb, and Hg. Additionally, the reutilization potential of biochar produced by post-phytoremediation plant residues as adsorbents was investigated. The results of adsorption experiments revealed that all biochars have an excellent performance to adsorb Pb(II), and the maximum adsorption capacity is 139.16 mg g^-1 for CC₄₅₀. The adsorption mechanism could be attributed to complexation, electrostatic attraction, and cation exchange. This study demonstrates that pyrolysis is an effective and environment-friendly alternative method to stabilize heavy metals in plants, and their pyrolysis products can be reused for heavy metal adsorption.

Impact of catalytic hydrothermal treatment and Ca/Al-modified hydrochar on lability, sorption, and speciation of phosphorus in swine manure: Microscopic and spectroscopic investigations

The effects of catalytic hydrothermal (HT) pretreatment on animal manure followed by the addition of hydrochar on the nutrients recovery have not yet been investigated using a combination of chemical, microscopic, and spectroscopic techniques. Therefore, a catalytic HT process was employed to pretreat swine manure without additives (manure-HT) and with H₂O₂ addition (manure-HT- H₂O₂) to improve the conversion efficiency of labile or organic phosphorus (P) to inorganic phase. Then, a Ca-Al layered double hydroxide hydrochar (Ca/Al LDH@HC) derived from corn cob biomass was synthesized and applied to enhance P sorption. Scanning electron microscopy (SEM), and three-dimensional excitation emission matrix (3D-EEM), X-ray photoelectron spectroscopy (XPS), P k-edge X-ray absorption near edge structure (XANES), were used to elucidate the mechanisms of P release and capture. The H₂O₂ assisted HT treatment significantly enhanced the release of inorganic P (251.4 mg/L) as compared to the untreated manure (57.2 mg/L). The 3D-EEM analysis indicated that the labile or organic P was transformed and solubilized efficiently along with the deconstruction of manure components after the H₂O₂ assisted HT pretreatment. Application of Ca/Al LDH@HC improved the removal efficiency of P from the derived P-rich HT liquid. This sorption process was conformed to the pseudo-second-order model, suggesting that chemisorption was the primary mechanism. The results of SEM and P k-edge XANES exhibited that Ca, as the dominated metal component, could act as a reaction site for the formation of phosphate precipitation. These results provide critical findings about recovering P from manure waste, which is useful for biowastes management and nutrients utilization, and mitigating unintended P loss and potential environmental risks.

A Comprehensive Review of Layered Double Hydroxide-Based Carbon Composites as an Environmental Multifunctional Material for Wastewater Treatment

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials.

Biochar-advanced thermocatalytic salvaging of the waste disposable mask with the production of hydrogen and mono-aromatic hydrocarbons

The salvaging of the waste disposable mask was conducted in this study through catalytic pyrolysis over corn stover derived biochar catalyst combined with the boosted generation of hydrogen and mono-aromatic hydrocarbons for the first time. In the absence of biochar, up to 53 wt% of wax was observed at 550 ºC, whereas at the biochar/mask ratio of 2, around 41 wt% of liquid oil was produced without the formation of wax. The hydrogen content in the gas stream was about 26 vol% at 600 ºC for non-catalytic pyrolysis, which increased to around 55 vol% at the expense of light hydrocarbons such as methane and C_2-4 for the catalytic process with the biochar/mask ratio of 3. In resulting liquid oil, the content of mono-aromatics, especially toluene, xylenes, and ethylbenzene was about 55% for catalytic runs, which was far greater than that of 38% from the non-catalytic run. Interestingly, the dyes released from mask pyrolysis could be completely captured/adsorbed by biochar, leading to a much cleaner oil. After 10 cycles of reuse at 600 ºC without regeneration, the biochar still held a good selectivity toward hydrogen and mono-aromatic hydrocarbons. This study exemplified a readily accessible concept and pathway of 'waste against waste' targeted to upcycle waste disposable masks over biochar from biomass waste.

Investigation of non-isothermal pyrolysis kinetics of waste industrial hemp stem by three-parallel-reaction model

The evaluation of pyrolysis kinetics for waste industrial hemp stem (IHS) is essential to achieve the high-value utilization of agricultural waste. In present study, firstly, non-isothermal pyrolysis experiments of IHS were performed at different heating rates using a thermogravimetric analyzer. Then, the kinetic triplets (apparent activation energy, pre-exponential factor, and reaction mechanism) of the three pseudo components for IHS (hemicellulose, cellulose, and lignin) were determined by a three-parallel-reaction model. Moreover, the pyrolysis products were also characterized via FTIR and SEM. The results showed that the apparent activation energies of hemicellulose, cellulose and lignin were 86.523, 113.257 and 197.961 kJ/mol, respectively; the pre-exponential factors were 6.887 × 10⁷, 8.179 × 10⁹ and 1.801 × 10¹⁵ s^-1, respectively; and the reaction mechanism functions were f(α) = α^1.35629(1-α)^0.34832[-ln(1-α)]^-1.20128, f(α) = α^3.42900(1-α)^0.01288[-ln(1-α)]^-2.84445, f(α) = α^0.68738(1-α)^3.09313[-ln(1-α)]^-1.58522, respectively. The release temperature for volatile products of IHS pyrolysis was mainly between 440 and 840 K. IHS as an agricultural waste is a suitable feedstock to produce renewable energy.

One-step synthesis of garlic peel derived biochar by concentrated sulfuric acid: Enhanced adsorption capacities for Enrofloxacin and interfacial interaction mechanisms

This study put forward a one-step carbonization method by concentrated sulfuric acid to prepare garlic peel derived biochar, and the synthetic conditions were optimized by L₁₆(4⁵) orthogonal experiments. Notably, in order to study the differences between the proposed synthetic method and the conventional pyrolysis method, the concentrated sulfuric acid carbonized garlic peels biochar (CSGPB) was compared with pyrolysis derived garlic peel biochar (HTGPB) in characterization and adsorption capacities for Enrofloxacin (ENR). Results showed that CSGPB exhibited more graphite-like structures with more active functional groups on the surface, and the equilibrium adsorption capacity of CSGPB (142.3 mg g^-1) was 13.7 times of HTGPB (10.4 mg g^-1) under identical conditions. Moreover, the adsorption behaviors including adsorption kinetics, isotherms and thermodynamics of CSGPB for ENR were fully investigated and discussed. Based on the above experiments, density functional theory (DFT) simulations were performed to reveal the interfacial interaction and adsorption mechanism. Results showed π-π interaction between quinolone moieties of ENR and graphite-like structures in CSGPB might be the dominant mechanism. As for the functional groups, the adsorption energies were -40.46, -15.21 and -5.96 kJ mol^-1 for -SO₃H, -OH and -COOH, respectively, which indicated -SO₃H was the most active functional groups on the surface of CSGPB. This study provided a new sustainable perspective for the design of efficient biochars, and explored the interfacial interaction mechanism of antibiotics removal on biochars.

Hydrogen-Rich Gas Production from Two-Stage Catalytic Pyrolysis of Pine Sawdust with Nano-NiO/Al2O3 Catalyst

Hydrogen production from biomass pyrolysis is economically and technologically attractive from the perspectives of energy and the environment. The two-stage catalytic pyrolysis of pine sawdust for hydrogen-rich gas production is investigated using nano-NiO/Al2O3 as the catalyst at high temperatures. The influences of residence time (0–30 s) and catalytic temperature (500–800 °C) on pyrolysis performance are examined in the distribution of pyrolysis products, gas composition, and gas properties. The results show that increasing the residence time decreased the solid and liquid products but increased gas products. Longer residence times could promote tar cracking and gas-phase conversion reactions and improve the syngas yield, H2/CO ratio, and carbon conversion. The nano-NiO/A12O3 exhibits excellent catalytic activity for tar removal, with a tar conversion rate of 93% at 800 °C. The high catalytic temperature could significantly improve H2 and CO yields by enhancing the decomposition of tar and gas-phase reactions between CO2 and CH4. The increasing catalytic temperature increases the dry gas yield and carbon conversion but decreases the H2/CO ratio and low heating value.

Facile Synthesis of Magnetic Biochar Derived from Burley Tobacco Stems towards Enhanced Cr (VI) Removal: Performance and Mechanism

In this study, ferric-loaded magnetic burley tobacco stem biochar (MBTS) was synthesized via pyrolysis to improve the removal of Cr(VI). The results showed that MBTS had an adsorption capacity of 54.92 mg Cr(VI)/g, which was about 14 times higher than raw burley tobacco stem biochar (i.e., 3.84 mg/g). According to the findings obtained, a three-step mechanism of Cr(VI) removal by MBTS was further put forward, i.e., (1) Cr(VI) exchanged with hydroxyl groups on MBTS, (2) the reduction in Cr(VI) to Cr(III) mediated by oxygen-containing groups, and (3) the chelation of produced Cr(III) with the amino groups on MBTS. FTIR spectra further revealed that C-N, C-H, and C=C groups played an important role in Cr(VI) removal. Furthermore, the adsorption equilibrium and kinetics of Cr(VI) on MBTS could better be described by the Langmuir equation and pseudo-second-order rate equation. This study clearly demonstrated that ferric-loaded biochar derived from burley tobacco stems could serve as a cost-effective magnetic adsorbent for the high-efficiency removal of soluble Cr(VI) from wastewater. Tobacco stem-adsorbed Cr(VI) realized a green path for treating waste by waste.

A state-of-the-art review on producing engineered biochar from shellfish waste and its application in aquaculture wastewater treatment

Global production of shellfish aquaculture is steadily increasing owing to the growing market demands for shellfish. The intensification of shellfish aquaculture to maximize production rate has led to increased generation of aquaculture waste streams, particularly the effluents and shellfish wastes. If not effectively managed, these wastes could pose serious threats to human health and the ecosystem while compromising the overall sustainability of the industry. The present work comprehensively reviews the source, composition, and environmental implications of shellfish wastes and aquaculture wastewater. Moreover, recent advancements in the valorization of shellfish wastes into value-added biochar via emerging thermochemical and modification techniques are scrutinized. The utilization of the produced biochar in removing emerging pollutants from aquaculture wastewater is also discussed. It was revealed that shellfish waste-derived biochar exhibits relatively higher adsorption capacities (300-1500 mg/g) compared to lignocellulose biochar (<200 mg/g). The shellfish waste-derived biochar can be effectively employed for the removal of various contaminants such as antibiotics, heavy metals, and excessive nutrients from aquaculture wastewater. Finally, future research priorities and challenges faced to improve the sustainability of the shellfish aquaculture industry to effectively support global food security are elaborated. This review envisages that future studies should focus on the biorefinery concept to extract more useful compounds (e.g., carotenoid, chitin) from shellfish wastes for promoting environmental-friendly aquaculture.

Oriented conversion of agricultural bio-waste to value-added products - A schematic review towards key nutrient circulation

Agriculture bio-waste is one of the largest sectors for nutrient circulation and resource recovery. This review intends to summarize the possible scheme through coupling chemical conversion of crop straws to biochar and biological conversion of livestock waste to value-added products thus reaching key nutrient circulation. Chemical conversion of crop straws to biochar was reviewed through summarizing the preparation methods and functional modification of biochar. Then, high-solid two-phase anaerobic conversion of agriculture bio-waste to value-added products and improved performance of bio-conversion through byproduct gases reuse and biochar supplementation were reviewed. Finally, high quality compost production through amendment of biochar and residual digestate was proposed with analysis of reduced nitrogen emission and carbon balance. The biological mechanism of synergistic regulation of carbon and nitrogen loss during bio-conversion with biochar was also reviewed. This will provide a model for synergistic conversion of agricultural wastes to value added products pursuing key nutrient circulation.

Banana stem and leaf biochar as an effective adsorbent for cadmium and lead in aqueous solution

Lead (Pb) and cadmium (Cd) are toxic heavy metals commonly found in aqueous environments. Biochar as a green adsorbent generated from biomass feedstock may be used for effective removal of these heavy metals. This study investigated the adsorption kinetics and isotherms of Pb2+ and Cd2+ in aqueous solutions at different pH by biochar prepared from banana stem and leaf (BSL-BC) at 400 °C. Characterizations using scanning electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy showed that the synthesized BSL-BC had rough surface, porous structure, and oxygen-containing functional groups. The adsorption of Pb2+ and Cd2+ onto BSL-BC reached equilibrium in 8 h and 200 min, respectively, with faster adsorption attained at higher pH and the optimum pH occurred at 5 (Pb2+) and 8 (Cd2+). All adsorption kinetic data followed the pseudo-second-order rate model. The adsorption isotherm data of Pb2+ and Cd2+ could be well-described by the Langmuir and Freundlich models, respectively, whereas neither the Temkin or Dubinin-Radushkevich models provided satisfactory fitting results. The maximum adsorption capacities for Pb2+ and Cd2+ were 302.20 and 32.03 mg/g, respectively. The calculated mechanism contributions showed that complexation with oxygen-containing functional groups, ion exchange, mineral precipitation, and Pb2+/Cd2+-π coordination accounted for 0.1%, 8.4%, 88.8%, and 2.6% to Pb2+ adsorption, and 0.4%, 6.3%, 83.0%, and 10.4% to Cd2+ adsorption, respectively. Therefore, mineral precipitation was likely the major mechanism responsible for adsorption of both Pb2+ and Cd2+ by BSL-BC. The results suggest that the synthesized BSL-BC has great potential for adsorption of Pb2+ and Cd2+ from aqueous solutions.

Sewage sludge-derived biochar for the adsorptive removal of wastewater pollutants: A critical review

The production of biochar from sewage sludge pyrolysis is a promising approach to transform the waste resultant from wastewater treatment plants (WWTPs) to a potential adsorbent. The current review provides an up-to-date review regarding important aspects of sewage sludge pyrolysis, highlighting the process that results major solid fraction (biochar), as high-value product. Further, the physio-chemical characteristics of sewage-sludge derived biochar such as the elemental composition, specific surface area, pore size and volume, the functional groups, surface morphology and heavy metal content are discussed. Recent progress on adsorption of metals, emerging pollutants, dyes, nutrients and oil are discussed and the results are examined. The sewage sludge-derived biochar is a promising material that can make significant contributions on pollutants removal from water by adsorption and additional benefit of the management of huge volume of sewage. Considering all these aspects, this field of research still needs more attention from the researchers in the direction of the technological features and sustainability aspects.

Integrated Cascade Biorefinery Processes to Transform Woody Biomass Into Phenolic Monomers and Carbon Quantum Dots

A novel cascade biorefinery strategy toward phenolic monomers and carbon quantum dots (CQDs) is proposed here via coupling catalytic hydrogenolysis and hydrothermal treatment. Birch wood was first treated with catalytic hydrogenolysis to afford a high yield of monomeric phenols (44.6 wt%), in which 4-propanol guaiacol (10.2 wt%) and 4-propanol syringol (29.7 wt%) were identified as the two major phenolic products with 89% selectivity. An available carbohydrate pulp retaining 82.4% cellulose and 71.6% hemicellulose was also obtained simultaneously, which was further used for the synthesis of CQDs by a one-step hydrothermal process. The as-prepared CQDs exhibited excellent selectivity and detection limits for several heavy metal cations, especially for Fe³⁺ ions in an aqueous solution. Those cost-efficient CQDs showed great potential in fluorescent sensor in situ environmental analyses. These findings provide a promising path toward developing high-performance sensors on environmental monitoring and a new route for the high value-added utilization of lignocellulosic biomass.

Zinc-chromium layered double hydroxides anchored on carbon nanotube and biochar for ultrasound-assisted photocatalysis of rifampicin

In this study, ZnCr layered double hydroxide (LDH), ZnCr LDH/carbon nanotube (CNT), and ZnCr LDH/Biochar (BC) were synthesized and characterized by various analyses. The successful synthesis and the great crystallinity of the samples were consented by XRD analysis. SEM and TEM were applied to study the morphology of the synthesized samples. The simultaneous presence of C, Zn, and Cr elements was well confirmed by EDX and dot mapping analyses demonstrating the successful preparation of nanocomposites. According to the BET analysis, ZnCr LDH nanocomposites with BC and CNT had more specific surface area compared to ZnCr LDH alone. The catalytic performances of the samples were determined for the degradation of rifampicin (RF). The degradation efficiency of the sonophotocatalytic process in the presence of 0.6 g L^-1 of ZnCr LDH/BC toward 15 mg L^-1 of RF under 150 W ultrasound and visible light irradiation was found to be about 100% within 40 min. The influence of the reactive species on the sonophotocatalytic process was assessed via the addition of different scavengers (para-benzoquinone (p-BQ), formic acid (FA), isopropyl alcohol (IPA)), and enhancers (hydrogen peroxide and potassium persulfate). The GC-MS analysis was carried out and eleven by-products during the RF decomposition were detected.

Biomass as source for hydrochar and biochar production to recover phosphates from wastewater: A review on challenges, commercialization, and future perspectives

Excessive phosphate run-off with total phosphorus concentration greater than 20 μg P L^-1 triggers the growth of harmful algal species in waterbodies and potentially leads to eutrophication. This has severe negative implications on aquatic environment and impacts human health. The annual economic impact of harmful algal blooms is reported to be as high as $25 million for public health and commercial fishery sector, $29 million for recreation/tourism sector and $2 million for monitoring and management. Adsorption is widely considered as an effective and economic strategy to achieve extremely low concentration of phosphorus. The char produced by valorizing various waste biomasses have been gaining attention in phosphorus remediation owing to their availability, their ability to regenerate and reuse. This review paper exclusively focuses on utilizing hydrochar and biochar synthesized from waste biomass, respectively, through hydrothermal carbonization and slow pyrolysis to mitigate phosphorus concentration and potential strategies for handling the spent char. The key mechanisms involved in phosphate adsorption are electrostatic interaction, ion exchange and complexation. The maximum adsorption capacity of hydrochar and biochar ranges from 14-386 mg g^-1 and 3-887 mg g^-1, respectively. Hydrochar and biochar are cost-effective alternative to commercial activated carbon and spent char can be used for multiple adsorption cycles. Furthermore, extensive research studies on optimizing the feedstock, reaction and activation conditions coupled with technoeconomic analysis and life cycle assessment could pave way for commercialization of char-based adsorption technology.

Lignocellulosic biomass-based pyrolysis: A comprehensive review

The efficacious application of lignocellulosic biomass for the new valuable chemicals generation curbs the excessive dependency on fossil fuels. Among the various techniques available, pyrolysis has garnered much attention for conversion of lignocellulosic biomass (encompasses cellulose, hemicellulose and lignin components) into product of solid, liquid and gases by thermal decomposition in an efficient manner. Pyrolysis conversion mechanism can be outlined as formation of char, depolymerisation, fragmentation and other secondary reactions. This paper gives a deep insight about the pyrolytic behavior of the lignocellulosic components accompanied by its by-products. Also several parameters such as reaction environment, temperature, residence time and heating rate which has a great impact on the pyrolysis process are also elucidated in a detailed manner. In addition the environmental and economical facet of lignocellulosic biomass pyrolysis for commercialization at industrial scale is critically analyzed. This article also illustrates the prevailing challenges and inhibition in implementing lignocellulosic biomass based pyrolysis with possible solution.

Valorization of Vine Prunings by Slow Pyrolysis in a Fixed-Bed Reactor

The paper aimed at studying the slow pyrolysis of vine pruning waste in a fixed bed reactor and characterizing the pyrolysis products. Pyrolysis experiments were conducted for 60 min, using CO2 as a carrier gas and oxidizing agent. The distribution of biochar and bio-oil was dependent on variations in heat flux (4244–5777 W/m2), CO2 superficial velocity (0.004–0.008 m/s), and mean size of vegetal material (0.007–0.011 m). Relationships among these factors and process performances in terms of yields of biochar (0.286–0.328) and bio-oil (0.260–0.350), expressed as ratio between the final mass of pyrolysis product and initial mass of vegetal material, and final value of fixed bed temperature (401.1–486.5 °C) were established using a 23 factorial design. Proximate and ultimate analyses, FT-IR and SEM analyses, measurements of bulk density (0.112 ± 0.001 g/cm3), electrical conductivity (0.55 ± 0.03 dS/m), pH (10.35 ± 0.06), and water holding capacity (58.99 ± 14.51%) were performed for biochar. Water content (33.2 ± 1.27%), density (1.027 ± 0.014 g/cm3), pH (3.34 ± 0.02), refractive index (1.3553 ± 0.0027), and iodine value (87.98 ± 4.38 g I2/100 g bio-oil) were measured for bio-oil. Moreover, chemical composition of bio-oil was evaluated using GC-MS analysis, with 27 organic compounds being identified.

Catalytic Fast Pyrolysis of Soybean Straw Biomass for Glycolaldehyde-Rich Bio-oil Production and Subsequent Extraction

In this study, soybean straw (SS) as a promising source of glycolaldehyde-rich bio-oil production and extraction was investigated. Proximate and ultimate analysis of SS was performed to examine the feasibility and suitability of SS for thermochemical conversion design. The effect of the co-catalyst (CaCl₂ + ash) on glycolaldehyde concentration (%) was examined. Thermogravimetric-Fourier-transform infrared (TG-FTIR) analysis was applied to optimize the pyrolysis temperature and biomass-to-catalyst ratio for glycolaldehyde-rich bio-oil production. By TG-FTIR analysis, the highest glycolaldehyde concentration of 8.57% was obtained at 500 °C without the catalyst, while 12.76 and 13.56% were obtained with the catalyst at 500 °C for a 1:6 ratio of SS-to-CaCl₂ and a 1:4 ratio of SS-to-ash, respectively. Meanwhile, the highest glycolaldehyde concentrations (%) determined by gas chromatography-mass spectrometry (GC-MS) analysis for bio-oils produced at 500 °C (without the catalyst), a 1:6 ratio of SS-to-CaCl₂, and a 1:4 ratio of SS-to-ash were found to be 11.3, 17.1, and 16.8%, respectively. These outcomes were fully consistent with the TG-FTIR results. Moreover, the effect of temperature on product distribution was investigated, and the highest bio-oil yield was achieved at 500 °C as 56.1%. This research work aims to develop an environment-friendly extraction technique involving aqueous-based imitation for glycolaldehyde extraction with 23.6% yield. Meanwhile, proton nuclear magnetic resonance (¹H NMR) analysis was used to confirm the purity of the extracted glycolaldehyde, which was found as 91%.

Effect of nickel salts on the production of biochar derived from alkali lignin: properties and applications

The massive generation of alkali lignin, has aroused the attention of all walks of life, and an eco-friendly utilization approach needs to be exploited. Herein, a simple pretreatment method with nickel salts was developed for the valorisation of alkali lignin through slow pyrolysis. The pretreatment of nickel salts improved the foaming or swelling behaviors of alkali lignin upon heating, and the specific surface area and total pore size of biochars increased about thirteenfold and eighteenfold, respectively. Additionally, Ni⁰ particles were generated and embedded in the carbon matrix of biochars. The biochar from Ni(NO₃)₂ pretreated lignin catalyzed the selective hydrogenation of nitrobenzene, yielding 80.5% of aniline; and that from (CH₃COO)₂Ni pretreated lignin showed adsorption capacity of lead around 87.1 mg/g. Moreover, the NiCl₂ pretreatment contributed to the formation of 1,2-dihydroxybenzene, while Ni(SO₄)₂ was conducive to the production of 4-methylguaiacol.

O/N/P-doped biochar induced to enhance adsorption of sulfonamide with coexisting Cu2+/ Cr (VI) by air pre-oxidation

The aim of this work to study the effectiveness of newly synthesized O/N/P-doped biochar for the removal of antibiotics with coexisting heavy metals. This study developed a low-dose additive agent with air pre-oxidation (APO) to obtain O/N/P-doped biochar (ONPBC) at 650/350 °C pyrolysis temperature with adsorption amount of 76.99 mg·g^-1 (ONPBC650) and 62.33 mg·g^-1 (ONPBC350) for sulfapyridine (SPY), comparing to pristine biochar 9.25 mg·g^-1 (BC650) and 11.60 mg·g^-1 (BC350), indicating the adsorption capacity of biochar has been greatly improved after modification. The main sorption mechanisms were elucidated for ONPBC650 (surface physical sorption) and ONPBC350 (H-bonding). The coexisting Cu²⁺/Cr (VI) showed different inhibition effects on the adsorption of SPY by ONPBC650/350. Considering a trade-off between high adsorption capacity and low inhibition effect of coexisting heavy metals, economic low-temperature O/N/P-doped biochar such as ONPBC350 could be a preferred adsorbent for the removal of sulfonamide or similar organic pollutants from contaminated water.

Fast pyrolysis of torrefied holocellulose for producing long-chain ether precursors in a fluidized bed

Combining torrefaction with fast pyrolysis is an achievable route for producing long-chain ether precursors. The results of structural characterization for native and torrefied holocellulose indicated that with increasing torrefaction temperature, the crystallinity index (CrI) decreased slightly and then sharply increased; hydroxyls, O-acetyl branches, ether bond and β-1,4-glycosidic bond were eliminated but carbonyls increased. Maximum mass loss rate and apparent activation energy increased after torrefaction. With an increase in torrefaction temperature, gaseous yield continuously dropped, and liquid product yield climbed to the highest point of 49.04% for holocellulose torrefied at 240 °C (240CS). Torrefaction was unfavorable for the production of small-molecule gases. The bio-oil analysis demonstrated that the yield of acetic acid decreased from 6.35% to 1.43% with torrefaction temperature increasing from 105 °C to 260 °C. Significantly, yields of targeted compounds were dramatically improved after torrefaction, and 240CS afforded the maximum carbon yield of 14.79%.

Low-cost biochar adsorbents prepared from date and delonix regia seeds for heavy metal sorption

In this study, low-cost biochar as bio-adsorbents derived from locally accessible delonix regia seed and date seeds were explored for heavy metal environmental cleaning. These prepared biochars were characterized by proximate and elemental analyses, CHNS/O analysis, Fourier-transformed infrared spectroscopy and thermo-gravitational methods. Bio-sorbent's ability to adsorb arsenic ions in synthetic wastewater was studied and optimized at varying solution pH, adsorbent dose, and starting metal concentrations. Experimentation and optimization studies were also carried out with the help of Design-software 6.0.8. The trials were designed by using response-surface methods, which includes three components and stages of Box-Behnken design. Date seeds derived-biochars eliminated 95% of arsenic from synthetic wastewater, whereas Delonix regia seeds removed 93.8%. The kinetics, isotherms and mechanism of As adsorption were also postulated. This study proposes that these seed's biochars might be employed as an effective, low-cost, and environmentally friendly adsorbent to remove heavy metals from the environment.

Isothermal and Kinetic Investigation of Exploring the Potential of Citric Acid-Treated Trapa natans and Citrullus lanatus Peels for Biosorptive Removal of Brilliant Green Dye from Water

Trapa natans peels (TNPs) and Citrullus lanatus peels (CLPs) were utilized for the biosorptive removal of brilliant green dye (BGD), after modifying with citric acid. Characterization and surface morphology were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. For the removal of BGD by citric acid-treated Trapa natans peels (CA-TNPs), the optimum conditions were obtained with adsorbent dose 0.8 g, contact time 25 minutes, initial pH 5, temperature 30°C, and agitation speed 100 rpm, while for the citric acid-treated Citrullus lanatus peels (CA-CLPs), adsorbent dose 0.8 g, contact time 20 minutes, pH 5, temperature 30°C, and agitation speed 100 rpm gave optimum results. The qmax values obtained were 108.6, 128, 144.9, and 188.68 mg/g for R-TNP, CA-TNP, R-CLP, and CA-CLP, respectively, while the correlation coefficient (R2) values obtained were 0.985, 0.986, 0.985, and 0.998 for R-TNP, CA-TNP, R-CLP, and CA-CLP, respectively. These favor the Langmuir isotherm and pseudo-second-order kinetics, with negative (ΔG0) values of all adsorbents, determining that the adsorption phenomenon is exothermic and spontaneous in nature. Both citric acid-treated peels of Trapa natans and Citrullus lanatus were found suitable for bulk-scale eradication of hazardous, toxic, and carcinogenic basic cationic dyes.

Application of co-pyrolysis biochar for the adsorption and immobilization of heavy metals in contaminated environmental substrates

Heavy metal pollution has been considered as a serious threat to the environment and human in the past decades due to its toxic and unbiodegradable properties. Recently, extensive studies have been carried out on the removal of heavy metals, and various adsorption materials have been successfully developed. Among, biochar is a promising option because of its advantages of various biomass sources, abundant microporous channels and surface functional groups, as well as its attractive economic feasibility. However, the application of pristine biochar is limited by its low adsorption capacity and nonregenerative property. Co-pyrolysis biochar, produced from the pyrolysis of biomass with the addition of another biomass or non-biomass precursor, is potential in overcoming the limitation of pristine biochar and achieving superior performance for heavy metal adsorption and immobilization. Therefore, this article summarizes the recent advances in development and applications of co-pyrolysis biochar for adsorption and immobilization of various heavy metals in contaminated environmental substrates. In details, the production, characteristics and advantages of co-pyrolysis biochar are initially presented. Subsequently, the adsorption behaviors and mechanisms of different heavy metals (including Hg, Zn, Pb, Cu, Cd, Cr, As, etc.) in flue gas and wastewater by co-pyrolysis biochar are reviewed, as well as factors influencing their adsorption capacities. Meanwhile, the immobilization of heavy metals in both biochar itself and contaminated soils by co-pyrolysis biochar is discussed. Finally, the limitations of current studies and future prospects are proposed. It aims at providing a guideline for the exploitation and application of cost-effective and environmental-friendly co-pyrolysis biochar in the decontamination of environmental substrates.

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.

Current understanding in conversion and application of tea waste biomass: A review

Along with the increasing consumption of tea and its extracts, the amount of tea waste grows rapidly, which not only results in huge biomass loss, but also increases environmental stress. In past years, interest has been attracted on utilization of tea waste biomass, and a lot of work has been carried out. This review summarized the progress in conversion of tea waste by thermo-chemical and biological technologies and analyzed the property of the derived products and their performance in applications. It was found that biochar derived from tea waste had relatively large surface area, porous structures, and abundant functional groups, and could be used as bio-adsorbents and catalysts and electrochemical energy storage, while the cost of its largescale production should be evaluated. Profoundly, biological conversion, including ensiling and composting, was suggested to be an effective way to develop the tea waste biomass in practice due to its low-cost and specific functions.

Life cycle assessment of the integration of anaerobic digestion and pyrolysis for treatment of municipal solid waste

The integration of anaerobic digestion (AD) and pyrolysis (Py) could be a solution to economically utilize the organic fraction of municipal solid waste (OFMSW). However, it is not clear whether the environmental impact of the integrated pathway always outperforms the two single technologies. In this study, two integrated pathways (AD-Py, Py-AD) were compared with single AD and Py from the life cycle environmental impacts point of view. The results indicate that the environmental impacts of the four pathways are heavily dependent on their energy inputs and outputs. AD-Py is more environmentally friendly (-11.53 of total environmental impact /kg OFMSW) than single AD or Py. Py-AD exhibites the heaviest environmental burden (2.75 of total environmental impact /kg OFMSW) in all pathways. Therefore, AD-Py can be the top priority of treating OFMSW among the four pathways from the environmental viewpoint. This work could provide a theoretical support for the utilization of OFMSW.