Search Results (86)

Biochar serves as an effective adsorbent for the heavy metal cadmium, with its performance significantly influenced by its physicochemical properties and various environmental features. Traditional machine learning models, though adept at managing complex multi-feature relationships, rely heavily on expertise in feature engineering and hyperparameter optimization. To address these issues, this study employs an automated machine learning (AutoML) approach, automating feature selection and model optimization, coupled with an intuitive online graphical user interface, enhancing accessibility and generalizability. Comparative analysis of four AutoML frameworks (TPOT, FLAML, AutoGluon, H₂O AutoML) demonstrated that H₂O AutoML achieved the highest prediction accuracy (R² = 0.918). Key features influencing adsorption performance were identified as initial cadmium concentration (23%), stirring rate (14.7%), and the biochar H/C ratio (9.7%). Additionally, the maximum adsorption capacity of the biochar was determined to be 105 mg/g. Optimal production conditions for biochar were determined to be a pyrolysis temperature of 570–800 °C, a residence time of ≥2 h, and a heating rate of 3–10 °C/min to achieve an H/C ratio of <0.2. An online graphical user interface was developed to facilitate user interaction with the model. This study not only provides practical guidelines for optimizing biochar but also introduces a novel approach to modeling using AutoML. Full article

In this study, we examined the capacity of magnesium-amended biochar to recover nutrients from dairy processing wastewater (DPW). Our results suggest that biochar engineered with magnesium (Mg–BC) was successful at recovering over 3 mg of PO₄³⁻-P per gram of biochar (96%) in synthetic and raw DPW through a combination of adsorption and chemical precipitation. The addition of Mg–BC to increase the pH of the synthetic and raw DPW was likely important in promoting chemical precipitation and increased nutrient recovery. The Mg-dosed biochar also recovered 1.7 mg of NH₄⁺-N per gram of biochar (24%) from raw DPW. However, the raw biochar (R-BC) was only capable of recovering a maximum of 0.5 mg of PO₄³⁻-P and an insignificant amount (˂0.1 mg) of NH₄⁺-N per gram of biochar. Full article

Biochar, a porous carbonaceous material derived from the pyrolysis of biomass under oxygen-limited conditions, offers several advantages for environmental remediation, including a high specific surface area, ease of preparation, and abundant raw material sources. However, the application of pristine biochar is limited by its inherent physicochemical shortcomings, such as a lack of active functional groups and limited elemental compositions. To overcome these limitations, metal-modified biochars have garnered increasing attention. In particular, iron-manganese (Fe-Mn) modification significantly enhances the adsorption capacity, redox potential, and microbial activity of biochar, owing to the synergistic interactions between Fe and Mn. Iron-manganese-modified biochar (FM-BC) has demonstrated effective removal of heavy metals, organic matter, phosphate, and nitrate through mechanisms including mesoporous adsorption, redox reactions, complexation, electrostatic interactions, and precipitation. Moreover, FM-BC can improve soil physicochemical properties and support plant growth, highlighting its promising potential for broader environmental application. This review summarizes the preparation methods, environmental remediation mechanisms, and practical applications of FM-BC and discusses future directions in mechanism elucidation, biomass selection, and engineering implementation. Overall, FM-BC, with its tunable properties and multifunctional capabilities, emerges as a promising and efficient material for addressing complex environmental pollution challenges. Full article

Biochar-based adsorbents synthesized from agricultural wastes have emerged as economical and environmentally sustainable materials for water purification. In this study, coffee shell-derived biochars were synthesized via pyrolysis at 500 and 700 °C, with and without water washing, and comprehensively characterized to evaluate their potential for removing Rhodamine B (RhB) from aqueous solution. Structural and surface analyses indicated that a higher pyrolysis temperature enhanced pore development and aromaticity, whereas water washing effectively removed inorganic ash, thereby exposing additional active sites. Among all samples, water-washed biochar pyrolyzed at 700 °C (WCB700) exhibited the highest surface area (273.6 m²/g) and adsorption capacity (193.5 mg/g). The adsorption kinetics conformed to a pseudo-second-order model, indicating chemisorption, and the equilibrium data fit the Langmuir model, suggesting monolayer coverage. Mechanism analysis highlighted the roles of π–π stacking, hydrogen bonding, electrostatic interaction, and pore filling. Additionally, WCB700 retained more than 85% of its original capacity after five regeneration cycles, demonstrating excellent stability and reusability. This study presents an economical approach to valorizing coffee waste as well as provides mechanistic insights into optimizing biochar surface chemistry for enhanced dye removal. These findings support the application of engineered biochar in scalable and sustainable wastewater treatment technologies. Full article

A core tertiary wastewater reactive filtration technology, where continuously renewed hydrous ferric oxide coated sand is created in an upflow continuous backwash filter, has been adopted in about 100 water resource recovery facilities in several countries. Primarily focused on ultralow phosphorus discharge requirements to address nutrient pollution impacts and harmful algae blooms, the technology has also demonstrated the capacity to address high-efficiency removals of Hg, As, Zn, N, and other pollutants of concern, in addition to water quality needs met by common sand filtration, including total suspended solids. Recent work has demonstrated the capability of an additive iron–ozone catalytic oxidation process to the core reactive filtration technology platform to address micropollutants such as pharmaceuticals. Most recently, direct injection of frangible biochar into the reactive sand filter bed as a consumable reagent demonstrates a novel biochar water treatment technology in a platform that yields dose-dependent carbon negativity. In this work, the reactive filtration technology performance is reviewed from field pilot-scale to full-scale installation scenarios for nutrient removal and recovery applications. We also review the potential of the technology for nutrient recovery with the addition of biochar and micropollutant destructive removal with catalytic oxidation. Research exploration of this reactive filtration technology includes life cycle assessment (LCA) and techno-economic assessment to evaluate the environmental and economic impacts of this advanced water treatment technology. A recent LCA study of a pilot-scale field research and full-scale municipal system with over 2200 inventory elements shows a dose-dependent carbon negativity when biochar is injected into the process stream of reactive filtration. In this study, LCA demonstrates that reactive filtration has the potential as a negative emissions technology with −1.21 kg CO₂e/m³, where the negative contribution from the dosed biochar is −1.53 kg CO₂e/m³. In this biochar water treatment configuration, the system not only effectively removes pollutants from wastewater but also contributes to carbon sequestration and nutrient recovery for agriculture, making it a potentially valuable approach for sustainable water treatment. Full article

Waste biomass gasification can contribute to the production of alternative and environmentally sustainable green fuels. Research at the CREC–UWO (Chemical Reactor Engineering Center–University of Western Ontario) considers an integrated gasification process where both electrical power, biochar, and tar-free syngas suitable for alcohol synthesis are produced. In particular, the present review addresses the issues concerning tar removal from the syngas produced in a waste biomass gasifier via a catalytic post-gasification (CPG) downer unit. Various questions concerning CPG, such as reaction conditions, thermodynamics, a Tar Conversion Catalyst (TCC), and tar surrogate chemical species that can be employed for catalyst performance evaluations are reported. Catalyst performance-reported results were obtained in a fluidizable CREC Riser Simulator invented at CREC–UWO. The present review shows the suitability of the developed fluidizable Ni–Ceria γ-alumina catalyst, given the high level of tar removal it provides, the minimum coke that is formed with its use, and the adequate reforming of the syngas exiting the biomass waste gasifier, suitable for alcohol synthesis. Full article

The widespread implementation of anaerobic digestion (AD) systems for organic waste treatment is increasingly challenged by emerging contaminants, including microplastics (MPs), antibiotics, and heavy metals (HMs), which exhibit environmental persistence and pose risks to ecological and human health. This review critically examines the sources, transformation pathways, and advanced mitigation strategies for these contaminants within AD systems. MPs, primarily derived from fragmented plastics and personal care products, accumulate in digestates and act as vectors for adsorbing toxic additives and pathogens. Antibiotics, introduced via livestock manure and wastewater, exert selective pressures that propagate antibiotic resistance genes (ARGs) while disrupting methanogenic consortia. HMs, originating from industrial and agricultural activities, impair microbial activity through bioaccumulation and enzymatic interference, with their bioavailability modulated by speciation shifts during digestion. To combat these challenges, promising mitigation approaches include the following: (1) bioaugmentation with specialized microbial consortia to enhance contaminant degradation and stabilize HMs; (2) thermal hydrolysis pretreatment to break down MPs and antibiotic residues; (3) chemical passivation using biochar or sulfides to immobilize HMs. Co-digestion practices inadvertently concentrate these contaminants, with MPs and HMs predominantly partitioning into solid phases, while antibiotics persist in both liquid and solid fractions. These findings highlight the urgency of optimizing mitigation strategies to minimize contaminant mobility and toxicity. However, critical knowledge gaps persist regarding the long-term impacts of biodegradable MPs, antibiotic transformation byproducts, and standardized regulatory thresholds for contaminant residues in digestate. This synthesis underscores the necessity for integrated engineering solutions and policy frameworks to ensure the safe resource recovery from AD systems, balancing energy production with environmental sustainability. Full article

Organic soil pollution poses a persistent threat to environmental sustainability by disrupting nutrient cycling and ecosystem functioning. The biochar-activated persulfate (PS)-based advanced oxidation process (AOP) has emerged as a promising strategy for the sustainable remediation of organic-contaminated soils. This review provides a comprehensive overview of the recent progress in the PS-based degradation of organic pollutants, with a particular focus on the role of biochar as an efficient and environmental activator. This review further summarizes advancements in the design of modified biochars, including metal (Fe, Cu, Co, Mn, Zn, and La), non-metal (N, S, B, P), and functional group modifications, aimed at enhancing the PS activation efficiency while minimizing secondary environmental risks. Importantly, the overlooked contributions of soil microorganisms in PS/biochar systems are discussed, highlighting their potential to complement chemical oxidation and contribute to eco-compatible remediation pathways. This review emphasizes the sustainability-oriented evolution of PS/biochar technology, highlighting the importance of a cost-efficient implementation, ecological compatibility, and the rational engineering of smart, regenerable catalysts. These insights support the advancement of PS/biochar-based AOPs toward scalable, intelligent, and environmentally sustainable soil remediation. Full article

Polycyclic aromatic hydrocarbons (PAHs) in biochar, as opposed to those in pyrolysis liquid products that exit the reactor without adhering to the solid product, are particularly undesirable due to their environmental persistence and potential toxicity. When applied as a soil amendment, biochar containing PAHs poses risks to soil ecosystems and human health. Their formation during pyrolysis presents a significant challenge in biochar production, requiring the optimization of pyrolysis process parameters to minimize PAH content for safe soil amendment applications. This study explored the effects of particle size and heating rate on PAH formation during corn cob pyrolysis. Thermogravimetric analysis (TGA) was employed to heat corn cob powder of varying sample masses from ambient temperature to 550 °C at heating rates of 5, 10, and 20 °C/min. Simultaneously, the Chemical Reaction Engineering and Chemical Kinetics (CRECK) model simulated the pyrolysis of spherical corn cob biomass particles with a radius ranging from 1 to 40 mm, using feedstock chemical compositions as inputs. Tar species generated from the solid biomass model were introduced into a gas-phase batch reactor model to evaluate PAH formation. The results demonstrate that the particle size and heating rate significantly affect PAH formation, shedding light on the complex dynamics of biomass pyrolysis. A single spherical particle with a radius close to 1 mm approximates ideal TGA conditions by minimizing temperature and mass transfer limitations. The CRECK model suggested that a particle radius of 5–10 mm, combined with a low heating rate of 5 °C/min, optimally reduces PAH formation. Future research should focus on using thermogravimetric analysis coupled with gas chromatography–mass spectrometry (TGA-GC-MS) to comprehensively quantify PAH species formation. Full article

Collapsible loess poses significant geotechnical risks due to its metastable structure and water sensitivity, while conventional stabilization methods often lack sustainability. This study investigates the synergistic effects of microbial-induced carbonate precipitation (MICP) and modified biochar (MBC) to enhance loess engineering properties. Controlled experiments evaluated hydraulic conductivity, shear strength, and stress-strress–strain behavior under varying MBC content (0–8%), cementation reagent concentration (0.5–1.5 mol/L), and confining pressures (50–400 kPa), and complemented by microstructural characterization via scanning electron microscope (SEM). Results demonstrate that MBC (4–6%) optimizes calcium carbonate distribution by providing nucleation sites, reducing hydraulic conductivity by 72% and increasing shear strength by 52% when compared with untreated loess. Elevated confining pressures (200–400 kPa) transformed brittle failure into ductile behavior through particle interlocking, with peak strength quadrupling under 400 kPa. SEM analysis revealed MBC stabilizes hierarchical pore networks: macropores sustain microbial activity, while mesopores are occluded by CaCO₃-MBC composites, sequestering ionic byproducts to mitigate efflorescence. The optimal combination (6% MBC, 1.0 mol/L reagent, 200 kPa confinement) achieved 85% of maximum strength gain at reduced reagent cost, balancing performance and sustainability. Full article

The excessive levels of neonicotinoid insecticides, particularly thiacloprid (THI), in the environment have become a significant threat to ecosystems. This study investigates the catalytic degradation of THI using pinewood biochar (PBC), zero-valent iron (ZVI), and ZVI/PBC composite, with a particular focus on the reaction activity modulation mediated by organic acids (humic acid: HA and oxalic acid: OA). Reductive dechlorination dominated THI degradation as observed by Cl⁻ release kinetics. Compared to HA (39.73%), the OA (73.44%) addition markedly increased the THI removal efficiency by ZVI/PBC, which alone has a lower removal efficacy, i.e., 37.29%. The increase in the THI removal rate was attributed to its enhanced electron transfer capacity. As confirmed by electrochemical characterization, the addition of organic acids promotes electron transfer between THI and catalysts (ZVI, PBC, or ZVI/PBC), thereby improving the removal efficiency of THI. XRD/XPS analyses elucidated that OA preferentially converted passivating Fe₂O₃/Fe₃O₄ on ZVI/PBC to reactive FeOOH and formed electron-conductive Fe–COO bonds, thereby suppressing oxide layer formation. PBC amplified these effects through ZVI dispersion and electron shuttling, reducing aggregation-induced activity loss. These findings provide a mechanistic framework for optimizing ligand-engineered iron composites, offering practical strategies to enhance pesticide remediation efficiency in organic acid-rich environmental systems. Full article

The extensive utilization of nano-zero-valent iron (nZVI) and its engineered derivatives has prompted significant environmental concerns, particularly regarding their phytotoxicological impacts, which remain inadequately characterized. This investigation systematically evaluated the phytotoxicological responses induced by nZVI, Chlorella vulgaris biochar (BC), and Chlorella vulgaris biochar loaded with nano-zero-valent iron (BC/nZVI) on mung bean seed germination and subsequent seedling development. The experimental data revealed that both the nZVI and BC/nZVI treatments significantly suppressed the germination indices, including germination rate, radicle and plumule elongation, and biomass accumulation, with nZVI demonstrating the most pronounced inhibitory effects. During the vegetative growth phases, nZVI exposure substantially impaired plant morphogenesis, manifested through reduced vertical growth, diminished fresh and dry biomass production, and the onset of premature foliar chlorosis, necrosis, desiccation, and, ultimately, plant mortality. A comparative analysis indicated that the BC/nZVI composites exhibited less severe photosynthetic inhibition relative to pristine nZVI. Biochemical assays demonstrated that nZVI exposure elicited the substantial upregulation in antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), concomitant with abnormal ferric ion accumulation in root tissues. Notably, BC/nZVI composites demonstrated the partial mitigation of these physiological disturbances. These empirical findings underscore that excessive iron bioavailability from nZVI induces substantial phytotoxicological stress, while BC matrix incorporation provides the partial amelioration of these adverse effects on seedling ontogeny. Full article

Amid the pressing challenge of global climate change, biogas (marsh gas) has garnered recognition as a clean and renewable energy source with significant potential to reduce greenhouse gas emissions and support sustainable energy production. Composed primarily of methane (CH₄) and carbon dioxide (CO₂), enhancing the CH₄ content in biogas is essential for improving its quality and expanding its high-value applications. This review examines the mechanisms underlying CH₄ and CO₂ production in anaerobic digestion (AD) processes; investigates the effects of raw material types, process routes, and fermentation conditions on biogas production and CH₄ content; and proposes feasible technical pathways for producing CH₄-rich biogas. Research indicates that CH₄-rich biogas can be produced through various strategies. Raw material pretreatment technologies and co-digestion strategies can enhance substrate performance, stabilize the AD process, and boost CH₄ production. Process optimizations, such as multiphase AD and CH₄ co-production techniques, significantly improve carbon utilization efficiency. Introducing exogenous reinforcement materials, including biochar and zero-valent iron nanoparticles, fosters microbial interactions and facilitates direct interspecies electron transfer (DIET). Furthermore, microbial regulation through genetic engineering and microbial community design presents promising prospects. By reviewing the mechanisms of gas production, influencing factors, and feasible pathways, this work aims to provide valuable insights for the technical research of AD to produce CH₄-rich biogas. Full article

This review explores biochar’s potential as a sustainable and cost-effective solution for remediating organic pollutants, particularly polycyclic aromatic hydrocarbons (PAHs) and pesticides, in water. Biochar, a carbon-rich material produced from biomass pyrolysis, has demonstrated adsorption efficiencies exceeding 90% under optimal conditions, depending on the feedstock type, pyrolysis temperature, and functionalization. High surface area (up to 1500 m²/g), porosity, and modifiable surface functional groups make biochar effective in adsorbing a wide range of contaminants, including toxic metals, organic pollutants, and nutrients. Recent advancements in biochar production, such as chemical activation and post-treatment modifications, have enhanced adsorption capacities, with engineered biochar achieving superior performance in treating industrial, municipal, and agricultural effluents. However, scaling up biochar applications from laboratory research to field-scale wastewater treatment poses significant challenges. These include inconsistencies in adsorption performance under variable environmental conditions, the high cost of large-scale biochar production, logistical challenges in handling and deploying biochar at scale, and the need for integration with existing treatment systems. Such challenges impact the practical implementation of biochar-based remediation technologies, requiring further investigation into cost-effective production methods, long-term performance assessments, and field-level optimization strategies. This review underscores the importance of addressing these barriers and highlights biochar’s potential to offer a sustainable, environmentally friendly, and economically viable solution for large-scale wastewater treatment. Full article

This study investigates Miscanthus biochar’s potential to reduce ammonia (NH₃) emissions in poultry production. Biochar from lignocellulosic biomass has proven a versatile tool in environmental remediation for water, soil, and air quality applications with ample opportunity for inclusion in agricultural systems. Ammonia emissions present a concern for animal/human health and the environment. The impacts of biochar production temperature (400 and 700 °C), organic acid activation (acetic acid, citric acid), and application rate (0.24 and 0.49 kg m⁻²) on broiler litter NH₃ emissions were evaluated. Biochar production parameters, i.e., temperature, and acid type were found to significantly impact its performance as an NH₃ control measure. The following factors, ranked by magnitude of impact, were found to statistically impact the NH₃ emission rate: biochar application rate (p < 0.001), biochar production temperature (p = 0.003), and lastly acid type (p = 0.007). The best performing biochar was produced at 400 °C, activated with acetic acid, and applied at a high addition rate (0.49 kg m⁻²). This treatment reduced cumulative NH₃ volatilization after 2 weeks by 19.7%. Full article