Response of soil characteristics to biochar and Fe-Mn oxide-modified biochar application in phthalate-contaminated fluvo-aquic soils

Application of iron-modified biochar in the fields of adsorption and degradation of antibiotics

Antibiotics, as emerging contaminants, have led to persistent global pollution issues, prompting long-standing attention on methods for their effective removal. Among various methods, iron-modified biochar stood out for its ability to adsorb and degrade antibiotics in the environment because biochar can provide a porous structure and oxygen-rich functional groups for efficient antibiotic adsorption, while the Fe2+/Fe3+ redox cycle in the iron modification biochar enhanced electronic transmission and further increased degradation. This review systematically summarized preparation methods of different iron-modified biochar, the adsorption capacities, mechanisms, and influencing factors of pollutants. It also explored the co-activation of iron and biochar, which enhanced the release of free radicals through Fenton-like oxidation pathways and accelerated degradation through photocatalytic electron-hole pair production. Additionally, the relationship between adsorption and degradation was discussed. Notably, an environmental risk assessment of iron-modified biochar and disposal of the used iron-modified biochar were discussed, which were critical for practical applications. Finally, the review highlighted the future directions of antibiotic pollution control and the broader potential of iron-modified biochar.

Advancing modified biochar for sustainable agriculture: a comprehensive review on characterization, analysis, and soil performance

Biochar is a carbon-rich material produced through the pyrolysis of various feedstocks. It can be further modified to enhance its properties and is referred to as modified biochar (MB). The research interest in MB application in soil has been on the surge over the past decade. However, the potential benefits of MB are considerable, and its efficiency can be subject to various influencing factors. For instance, unknown physicochemical characteristics, outdated analytical techniques, and a limited understanding of soil factors that could impact its effectiveness after application. This paper reviewed the recent literature pertaining to MB and its evolved physicochemical characteristics to provide a comprehensive understanding beyond synthesis techniques. These include surface area, porosity, alkalinity, pH, elemental composition, and functional groups. Furthermore, it explored innovative analytical methods for characterizing these properties and evaluating their effectiveness in soil applications. In addition to exploring the potential benefits and limitations of utilizing MB as a soil amendment, this article delved into the soil factors that influence its efficacy, along with the latest research findings and advancements in MB technology. Overall, this study will facilitate the synthesis of current knowledge and the identification of gaps in our understanding of MB.

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Enhancing neonicotinoid removal in recirculating constructed wetlands: The impact of Fe/Mn biochar and microbial interactions

Neonicotinoids pose significant environmental risks due to their widespread use, persistence, and challenges in elimination. This study explores the effectiveness of Fe/Mn biochar in enhancing the removal efficiency of neonicotinoids in recirculating constructed wetlands (RCWs). Results demonstrated that incorporating Fe/Mn biochar into RCWs significantly improved the removal of COD, NH4+-N, TN, TP, imidacloprid (IMI), and acetamiprid (ACE). However, the simultaneous presence of IMI and ACE in the RCWs hindered the elimination of NH4+-N, TN, and TP from wastewater. The enhanced removal of nutrients and pollutants by Fe/Mn biochar was attributed to its promotion of carbon, nitrogen, and phosphorus cycling in RCWs, along with its facilitation of the adsorption and biodegradation of IMI and ACE. Metagenomics analysis demonstrated that Fe/Mn biochar altered the structure and diversity of microbial communities in RCWs. A total of 17 biodegradation genes (BDGs) and two pesticide degradation genes (PDGs) were identified within RCWs, with Fe/Mn biochar significantly increasing the abundance of BDGs such as cytochrome P450. The potential host genera for these BDGs/PDGs were identified as Betaproteobacteria, Acidobacteria, Nitrospiraceae, Gemmatimonadetes, and Bacillus. This study offers valuable insights into how Fe/Mn biochar enhances pesticide removal and its potential application in constructed wetland systems for treating pesticide-contaminated wastewater.

A novel magnetic graphene-loaded biochar gel for the remediation of arsenic- and antimony-contaminated mining soil

Metalloid co-contamination such as arsenic (As) and antimony (Sb) in soils has posed a significant threat to ecological balance and human well-being. In this study, a novel magnetic graphene-loaded biochar gel (FeBG) was developed, and its remediation potential for the reclamation of AsSb spoiled soil was assessed through a six-month soil incubation experiment. Results showed that the incorporation of iron substances and graphene imparted FeBG with enhanced surface characteristics, such as the formation of a new FeO bond and an enlarged surface area compared to the pristine biochar (BC) (80.5 m2 g-1 vs 57.4 m2 g-1). Application of FeBG significantly decreased Na2HPO4-extractable concentration of As in soils by 9.9 %, whilst BC addition had a non-significant influence on As availability, compared to the control. Additionally, both BC (8.2 %) and FeBG (16.4 %) treatments decreased the Na2HPO4-extractable concentration of Sb in soils. The enhanced immobilization efficiency of FeBG for As/Sb could be attributed to FeBG-induced electrostatic attraction, complexation (Fe-O(H)-As/Sb), and π-π electron donor-acceptor coordination mechanisms. Additionally, the FeBG application boosted the activities of sucrase (9.6 %) and leucine aminopeptidase (7.7 %), compared to the control. PLS-PM analysis revealed a significant negative impact of soil physicochemical properties on the availability of As (β = -0.611, P < 0.01) and Sb (β = -0.848, P < 0.001) in soils, in which Sb availability subsequently led to a suppression in soil enzyme activities (β = -0.514, P < 0.01). Overall, the novel FeBG could be a potential amendment for the simultaneous stabilization of As/Sb and the improvement of soil quality in contaminated soils.

Mechanisms of biochar assisted di-2-ethylhexyl phthalate (DEHP) biodegradation in tomato rhizosphere by metabolic and metagenomic analysis

The intensive accumulation of di-2-ethylhexyl phthalate (DEHP) in agricultural soils has resulted in severe environmental pollution that endangers ecosystem and human health. Biochar is an eco-friendly material that can help in accelerating organic pollutant degradation; nevertheless, its roles in enhancing DEHP removal in rhizosphere remain unclear. This work investigated the impacts of biochar dosage (0%-2.0%) on DEHP degradation performance in tomato rhizosphere by comprehensively exploring the change in DEHP metabolites, bacterial communities and DEHP-degrading genes. Our results showed a significant increase of rhizosphere pH, organic matter and humus by biochar amendment, which achieved a satisfactorily higher DEHP removal efficiency, maximally 77.53% in treatments with 1.0% of biochar. Biochar addition also remarkably changed rhizosphere bacterial communities by enriching some potential DEHP degraders of Nocardioides, Sphingomonas, Bradyrhizobium and Rhodanobacter. The abundance of genes encoding key enzymes (hydrolase, esterase and cytochrome P450) and DEHP-degrading genes (pht3, pht4, pht5, benC-xylZ and benD-xylL) were increased after biochar amendment, leading to the change in DEHP degradation metabolism, primarily from benzoic acid pathway to protocatechuic acid pathway. Our findings evidenced that biochar amendment could accelerate DEHP degradation by altering rhizosphere soil physicochemical variables, bacterial community composition and metabolic genes, providing clues for the mechanisms of biochar-assisted DEHP degradation in organic contaminated farmland soils.

Application of compost assisted by Fe3O4 nanoparticles in di (2-ethylhexyl) phthalate-contaminated soil remediation: Biostimulation strategy, Soil responses, and RSM/CCD Optimization

Globally, contamination of agricultural soils by phthalate esters (PAEs) caused by direct consumption of plastic mulch films has been confirmed. The most widely used plasticizer is di (2-ethylhexyl) phthalate (DEHP), which is a more recalcitrant endocrine-disrupting chemical (EDC). Because of its low solubility and hydrophobicity, it remains in the soil longer, causes bioaccumulation in agricultural products, and has negative repercussions for food safety. In this study, the performance of kitchen organic waste compost assisted by Fe3O4 nanoparticles in DEHP removal efficiency (%) and soil C:N ratio (two responses) was optimized using Response Surface Methodology (RSM) based on Central Composite Design (CCD) in Design-Expert software (11.0.3.0). Under optimum conditions, a DEHP concentration of 10 mg·kg-1 (dw soil), a retention time of 35 days, an NPs dose of 0.99 g·kg-1 (media), a removal efficiency of 91.6 %, and a soil C:N ratio of 10.5 with a desirability of 0.963 were determined. A quadratic model (P-value <0.0001, adjusted R2 = 0.974 (Y1), 0.943 (Y2)) was used to predict the variables and their interactions. The agricultural soil responses in the treatments amended by compost and Fe3O4 NPs (SCN) showed a significant increase in SOM, TC, TN, AP, K, and Fe nutrients when compared to the control (P < 0.05). After 35 days, in the SC1N3 treatment (DEHP concentration = 10 mg·kg-1, NPs dose =1.2 g·kg-1), with higher DEHP removal efficiency (89.57 %), the C:N:P ratio was equal to 100: 9.75:0.69, and the total microbial colony count was 3.6 × 109 CFU/ml at pH 7.45. The study found that compost nutrients and Fe-based nanoparticle micronutrients can enhance DEHP degradation by stimulating the soil's native microflora. As a result, the synergistic potential of compost and Fe3O4 nanoparticles can be considered a promising, cost-effective, and agri-environmentally friendly approach in the "assisted bioremediation" strategy of DEHP-contaminated soils.

Performance and mechanisms of biochar-assisted vermicomposting in accelerating di-(2-ethylhexyl) phthalate biodegradation in farmland soil

Biochar and earthworms can accelerate di-(2-ethylhexyl) phthalate (DEHP) degradation in soils. However, little is known regarding the effect of biochar-assisted vermicomposting on soil DEHP degradation and the underlying mechanisms. Therefore, the present study investigated DEHP degradation performance and bacterial community changes in farmland soils using earthworms, biochar, or their combination. Biochar-assisted vermicomposting significantly improved DEHP degradation through initial physical adsorption on biochar and subsequent rapid biodegradation in the soil, earthworm gut, and charosphere. Burkholderiaceae, Pseudomonadaceae, and Flavobacteriaceae were the potential DEHP degraders and were enriched in biochar-assisted vermicomposting. In particularly, Burkholderiaceae and Sphingomonadaceae were enriched in the earthworm gut and charosphere, possibly explaining the mechanism of accelerated DEHP degradation in biochar-assisted vermicomposting. Soil pH, soil organic matter, and humus (humic acid, fulvic acid, and humin) increased by earthworms or biochar enhanced DEHP degradation. These findings imply that biochar-assisted vermicomposting enhances DEHP removal not only through rapid physical sorption but also through the improvement of soil physicochemical characteristics and promotion of degraders in the soil, earthworm gut, and charosphere. Overall, biochar-assisted vermicomposting is a suitable method for the remediation of organic-contaminated farmland soils.

Sewage sludge derived biochar for environmental improvement: Advances, challenges, and solutions

With the rapid growth yield of global sewage sludge, rational and effective treatment and disposal methods are becoming increasingly needed. Biochar preparation is an attractive option for sewage sludge treatment, the excellent physical and chemical properties of sludge derived biochar make it an attractive option for environmental improvement. Here, the current application state of sludge derived biochar was comprehensively reviewed, and the advances in the mechanism and capacity of sludge biochar in water contaminant removal, soil remediation, and carbon emission reduction were described, with particular attention to the key challenges involved, e.g., possible environmental risks and low efficiency. Several new strategies for overcoming sludge biochar application barriers to realize highly efficient environmental improvement were highlighted, including biochar modification, co-pyrolysis, feedstock selection and pretreatment. The insights offered in this review will facilitate further development of sewage sludge derived biochar, towards addressing the obstacles in its application in environmental improvement and global environmental crisis.

Recent developments in modification of biochar and its application in soil pollution control and ecoregulation

Soil pollution has become a real threat to mankind in the 21st century. On the one hand, soil pollution has reduced the world's arable land area, resulting in the contradiction between the world's population expansion and the shortage of arable land. On the other hand, soil pollution has seriously disrupted the soil ecological balance and significantly affected the biodiversity in the soil. Soil pollutants may further affect the survival, reproduction and health of humans and other organisms through the food chain. Several studies have suggested that biochar has the potential to act as a soil conditioner and to promote crop growth, and is widely used to remove environmental pollutants. Biochar modified by physical, chemical, and biological methods will affect the treatment efficiency of soil pollution, soil quality, soil ecology and interaction with organisms, especially with microorganisms. Therefore, in this review, we summarized several main biochar modification methods and the mechanisms of the modification and introduced the effects of the application of modified biochar to soil pollutant control, soil ecological regulation and soil nutrient regulation. We also introduced some case studies for the development of modified biochars suitable for different soil conditions, which plays a guiding role in the future development and application of modified biochar. In general, this review provides a reference for the green treatment of different soil pollutants by modified biochar and provides data support for the sustainable development of agriculture.

Biochar in environmental friendly fertilizers - Prospects of development products and technologies

According to the circular economy concept, the production of fertilizers should be closed in a loop, which prevents excessive emissions and harmful effects to the environment. Biological wastes are problematic to collect and transport. They undergo a biological transformation that causes greenhouse gases emission and sanitary hazards. Biomass sources used for organic or organo-mineral fertilizers must be free of pathogens and rich in macro and microelements. Solid residues can be processed thermally. Biochar is a carbon produced by biomass pyrolysis without oxygen presence and has been used for many years to improve soil quality and enhance the efficiency of fertilization. There are many research works on the use of biochar in fertilization. This study is also extended by the latest developments and technologies from the patent database (recent year) and biochar-based fertilizers market. To the best of our knowledge, there is no such review currently available in scientific databases. Based on the collected data, the best method of biochar management was proposed - soil application. Biochar applied to soil has several advantages: it improves soil structure and its sorption capacity, enhances soil-nutrient retention and water-holding capacity, immobilizes contaminants from soil (sorption), reduces greenhouse gas emissions and soil nutrient leaching losses while stimulating the growth of a plant.