Co-sorption/co-desorption mechanism of the mixed chlorobenzenes by fresh bulk and aged residual biochar

Environmental fate and transformation mechanisms of chlorinated organic pollutants from the petrochemical industry: Insights for pollution control and remediation

Chlorinated organic pollutants (Cl-OPs), highly toxic and environmentally persistent, have become the spotlight, particularly from petrochemical industry. This study focuses on environmental fate of Cl-OPs from petrochemical industry, and transformation mechanisms in multi-media, aiming to enhance pollution control and remediation strategies. Emitted from leakage and waste discharge, Cl-OPs, encompassing chlorinated volatile organic compounds (Cl-VOCs), traditional and emerging persistent organic pollutants (POPs), were prevalent with average concentrations of 10-6-103 μg/m3 in the atmosphere, 10-2-105 μg/kg in soil and 100-105 μg/L in groundwater. Significantly, emerging POPs, particularly hexachlorobutadiene (HCBD) and short-chain chlorinated paraffins (SCCPs), with concentrations comparable to Cl-VOCs, urgently need attention. Once into the environment, Cl-OPs are naturally transformed primarily through atmospheric oxidation and water photolysis induced by hydroxyl radical (‧OH), and microbial degradation. Despite challenges in atmospheric complete degradation, ‧OH in water effectively photolytically degrade chlorinated benzenes and paraffins facilitated by dissolved oxygen and organic matter. Microbial degradation, influenced by oxygen, temperature, and pH, is essential for Cl-OPs removal from water and soil, where oxidation make complete mineralization possible whereas dechlorination may generate higher toxic intermediates. Hence, Cl-OPs control necessitates an attentive to leakage and waste management. Furthermore, advanced ‧OH oxidation and microbial treatment are of effective remediation prospect.

Microbial community assemblage altered by coprecipitation of artificial humic substances and ferrihydrite: Implications for carbon fixation pathway transformation

The suppression of soil carbon mineralization has been demonstrated to be effectively facilitated by carbon‑iron interactions, yet the specific mechanisms by which artificial humic substances (A-HS) coupled with ferrihydrite influence this process remain insufficiently explored. This study is to investigate how the A-HS, specifically artificial fulvic acid (A-FA) and artificial humic acid (A-HA), coupled with ferrihydrite, affect carbon mineralization under anaerobic system that simulates paddy flooding conditions. The object is to investigate trends in carbon emissions and to delineate microbial community structure and functional pathways. The findings indicate that A-HA and A-FA substantially reduce CO2 and CH4 emissions, with A-FA having a particularly pronounced effect on carbon fixation, halving CO2 concentrations. The low concentration of Fe(II) observed suggest that A-FA and A-HA impede the dissimilatory iron reduction (DIR) process. Detailed 16S rDNA sequencing and gene prediction analyses reveal changes in microbial community structures and functions, highlighting Methanobacterium as the dominant hydrogenotrophic methanogens. The reductive citric acid cycle, predominantly utilized by Clostridium carboxidivorans, was identified as the principal carbon fixation pathway. This work provides a novel insight into the microbial mechanisms of carbon sequestration and highlights the potential of A-HS in improving soil fertility and contributing to climate change mitigation through enhancing soil carbon storage.

Engineered biochars for simultaneous immobilization of as and Cd in soil: Field evidence

Agricultural soil contamination by potentially toxic elements (PTEs) such as arsenic (As) and cadmium (Cd) poses a serious threat to food security. Immobilization serves as a widely used approach for the remediation of PTEs contaminated soils, nevertheless, the long-term effectiveness for the simultaneous immobilization of both cations and oxyanions remains a challenge. In order to effectively enhance the synergistic immobilization effect of soil As and Cd contaminated by multiple elements and improve the ecological environment of farmland. In this study, a typical polluted tailings area farmland was selected for situ immobilization experiments, and biochar was prepared from cow manure (CMB), rice straw (RSB), and pine wood (PWB) as raw materials. On this basis, the pristine biochar was modified with ferric chloride (F), potassium permanganate (K), magnesium chloride (M), and aluminum chloride (A), respectively. Furthermore, the immobilization effect of modified biochar on As-Cd and the stress effect on soil respiration were investigated. The results showed that CMB and RSB reduced the bioavailability of heavy metals, potassium permanganate has strong oxidizing properties, and the strong oxidability of potassium permanganate stimulated the generation of more oxygen-containing functional groups on the surface of biochar, thereby enhancing the adsorption and complexation effect of modified materials on As and Cd. Among them, the extracted Cd concentration of Diethylenetriamine pentaacetic acid (DTPA) in KCMB and KRSB in 2020 decreased by 8.23-43.12% and 9.67-35.29% compared to other treatments, respectively. Meanwhile, the KCMB and KRSB treatments also reduced the enrichment of As and Cd in plant tissues. In addition, the dissolved organic carbon (DOC) content in KCMB treatment was relatively high, and the carbon stability of the material was weakened. Simultaneously, the soil respiration emission of KCMB treatment was increased by 5.63% and 11.93% compared to KRSB and KPWB treatments, respectively. In addition, the structural equation also shows that DOC has a large positive effect on soil respiration. In summary, the KRSB treatment effectively achieve synergistic immobilization of As-Cd and provide important guiding significance for green and low-carbon remediation of polluted farmland.

Biochar-based composites for removing chlorinated organic pollutants: Applications, mechanisms, and perspectives

Chlorinated organic pollutants constitute a significant category of persistent organic pollutants due to their widespread presence in the environment, which is primarily attributed to the expansion of agricultural and industrial activities. These pollutants are characterized by their persistence, potent toxicity, and capability for long-range dispersion, emphasizing the importance of their eradication to mitigate environmental pollution. While conventional methods for removing chlorinated organic pollutants encompass advanced oxidation, catalytic oxidation, and bioremediation, the utilization of biochar has emerged as a prominent green and efficacious method in recent years. Here we review biochar's role in remediating typical chlorinated organics, including polychlorinated biphenyls (PCBs), triclosan (TCS), trichloroethene (TCE), tetrachloroethylene (PCE), organochlorine pesticides (OCPs), and chlorobenzenes (CBs). We focus on the impact of biochar material properties on the adsorption mechanisms of chlorinated organics. This review highlights the use of biochar as a sustainable and eco-friendly method for removing chlorinated organic pollutants, especially when combined with biological or chemical strategies. Biochar facilitates electron transfer efficiency between microorganisms, promoting the growth of dechlorinating bacteria and mitigating the toxicity of chlorinated organics through adsorption. Furthermore, biochar can activate processes such as advanced oxidation or nano zero-valent iron, generating free radicals to decompose chlorinated organic compounds. We observe a broader application of biochar and bioprocesses for treating chlorinated organic pollutants in soil, reducing environmental impacts. Conversely, for water-based pollutants, integrating biochar with chemical methods proved more effective, leading to superior purification results. This review contributes to the theoretical and practical application of biochar for removing environmental chlorinated organic pollutants.

Petroleum-contaminated soil bioremediation and microbial community succession induced by application of co-pyrolysis biochar amendment: An investigation of performances and mechanisms

This study aimed to remediate petroleum-contaminated soil using co-pyrolysis biochar derived from rice husk and cellulose. Rice husk and cellulose were mixed in various weight ratios (0:1, 1:0, 1:1, 1:3 and 3:1) and pyrolyzed under 500 °C. These biochar variants were labeled as R0C1, R1C0, R1C1, R1C3 and R3C1, respectively. Notably, the specific surface area and carbon content of the co- pyrolysis biochar increased, potentially promoting the growth and colonization of soil microorganisms. On the 60th day, the microbial control group achieved a 46.69% removal of pollutants, while the addition of R0C1, R1C0, R1C3, R1C1 and R3C1 resulted in removals of 70.56%, 67.01%, 67.62%, 68.74% and 67.30%, respectively. In contrast, the highest efficiency observed in the abiotic treatment group was only 24.12%. This suggested that the removal of petroleum pollutants was an outcome of the collaborative influence of co-pyrolysis biochar and soil microorganisms. Furthermore, the abundance of Proteobacteria, renowned for its petroleum degradation capability, obviously increased in the treatment group with the addition of co-pyrolysis biochar. This demonstrated that co-pyrolysis biochar could notably stimulate the growth of functionally associated microorganisms. This research confirmed the promising application of co-pyrolysis biochar in the remediation of petroleum-contaminated soil.

Current status and future challenges of chlorobenzenes pollution in soil and groundwater (CBsPSG) in the twenty-first century: a bibliometric analysis

The global industrial structure had undertaken significant changes since the twenty-first century, making a severe problem of chlorobenzene pollution in soil and groundwater (CBsPSG). CBsPSG receives increasing attention due to the high toxicity, persistence, and bioaccumulation of chlorobenzenes. To date, despite the gravity of this issue, no bibliometric analysis (BA) of CBsPSG does exist. This study fills up the gap by conducting a BA of 395 articles related to CBsPSG from the Web of Science Core Collection database using CiteSpace. Based on a comprehensive analysis of various aspects, including time-related, related disciplines, keywords, journal contribution, author productivity, and institute and country distribution, the status, development, and hotspots of research in the field were shown visually and statistically. Moreover, this study has also delved into the environmental behavior and remediation techniques of CBsPSG. In addition, four challenges (unequal research development, insufficient cooperation, deeply mechanism research, and developing new technologies) have been identified, and corresponding suggestions have been proposed for the future development of research in the field. Afterwards, the limitations of BA were discussed. This work provides a powerful insight into CBsPSG, enabling to quickly identify the hotspot and direction of future studies by relevant researchers.

Inorganic Skeleton Reinforcement-A Generic Approach to Improve the Mechanical Properties of Biochar

Biochar is considered as a promising candidate for emerging sustainable energy systems and environmental technology applications. However, the improvement of mechanical properties remains challenges. Herein, we propose a generic strategy to enhance the mechanical properties of bio-based carbon materials through inorganic skeleton reinforcement. As a proof-of-concept, silane, geopolymer, and inorganic gel are selected as precursors. The composites' structures are characterized and an inorganic skeleton reinforcement mechanism is elucidated. Specifically, two types of reinforcement of the silicon-oxygen skeleton network formed in situ with biomass pyrolysis and the silica-oxy-al-oxy network are constructed to improve the mechanical properties. A significant improvement in mechanical strength was achieved for bio-based carbon materials. The compressive strength of well-balanced porous carbon materials modified by silane can reach up to 88.9 kPa, geopolymer-modified carbon material exhibits an enhanced compressive strength of 36.8 kPa, and that of inorganic-gel-polymer-modified carbon material is 124.6 kPa. Moreover, the prepared carbon materials with enhanced mechanical properties show excellent adsorption performance and high reusability for organic pollutant model compound methylene blue dye. This work demonstrates a promising and universal strategy for enhancing the mechanical properties of biomass-derived porous carbon materials.

Wood Biochar Enhances the Valorisation of the Anaerobic Digestion of Chicken Manure

In this study, the efficacy of biochar to mitigate ammonia stress and improve methane production is investigated. Chicken manure (CM) was subjected to high-solid mesophilic anaerobic digestion (15% total solid content) with wood biochar (BC). Wood biochar was further treated using HNO3 and NaOH to produce acid–alkali-treated wood biochar (TBC), with an improvement in its overall ammonium adsorption capacity and porosity. Three treatments were loaded in triplicate into the digesters, without biochar, with biochar and with acid–alkali-treated biochar and maintained at 37 °C for 110 days. The study found a significant improvement in CH4 formation kinetics via enhanced substrate degradation, leading to CH4 production of 74.7 mL g−1 VS and 70.1 mL g−1 VS by BC and TBC treatments, compared to 39.5 mL g−1 VS by control treatments on the 28th day, respectively. However, only the use of TBC was able to prolong methane production during the semi-inhibition phase. The use of TBC also resulted in the highest removal of total ammonia nitrogen (TAN) of 86.3%. In addition, the treatment with TBC preserved the highest microbial biomass at day 110. The presence of TBC also resulted in an increase in electrical conductivity, possibly promoting DIET-mediated methanogenesis. Overall, the acid–alkali treatment of biochar can be a novel approach to improve biochar’s existing characteristics for its utilisation as an additive in anaerobic digestion.