Biochar For Remediation Research Articles

Remediation of uranium-contaminated acidic red soil by rice husk biochar.

Uranium (U) in the U-contaminated acidic red soil exhibits high mobility. In the present study, rice husk was used to produce biochar to remediate U-contaminated red soil under acid precipitation. Firstly, batch adsorption experiments showed that the dissolution of alkaline substance in biochar could buffer the pH value of acidic solution. The equilibrium pH value had a crucial influence on biochar adsorption capacity of U, and the neutral equilibrium pH value was favorable for adsorption. Then, the incubation experiments of red soil with biochar were performed, and the Synthetic Precipitation Leaching Procedure (SPLP) extraction of amended red soil showed that the short-term leachability of U was decreased from 26.53% in control group (without biochar) to 1.40% in 10% biochar-amended red soil. Subsequently, the sequential extraction showed that the fraction of U was mainly transformed from exchangeable and Fe/Mn oxide fraction to carbonate fraction after biochar amendment, and the total amount of exchangeable U and carbonate fraction U in soil was increased slightly. Finally, simulated acid rain leaching experiments showed that the capability of amended red soil to resist acid rain acidification was enhanced. And the long-term leachability of U in amended red soil was decreased from 26.37% in control group to 3.18% in the 10% biochar-amended red soil under the simulated acid rain leaching conditions. In conclusion, biochar has passivation effect on U in U-contaminated red soil, which can reduce the long-term and short-term mobility of U in acidic environments. This study provided an experimental basis for the application of biochar in remediation and improvement of U-contaminated acidic red soil.

Marked changes in biochar's ability to directly immobilize Cd in soil with aging: implication for biochar remediation of Cd-contaminated soil.

To investigate the change in biochar's ability to directly immobilize Cd in soil, a successive wheat cultivation experiment was conducted. Three biochars with different Cd adsorption mechanisms were added to the soils, and a mesh bag was used to separate the soil particles (> 1μm) from the biochar. The results showed that the ash contents and anionic contents (CO32- and PO43-) of the biochar decreased with the cultivation time, while the oxygen-containing functional group content and CEC of the biochar increased. As a result, the Cd concentration on biochar decreased, by 68.9% for WBC300, while unstable Cd species (acid soluble and reducible fraction of Cd) on biochar increased with successive cultivation, increasing from 3 to 17% for WBC300 in FS. Correspondingly, the ability of biochar to inhibit Cd accumulation in wheat decreased. The results of this study illustrated that the ability of biochar to directly immobilize Cd in soil is not permanent; it gradually decreases with aging in soil. The adsorption mechanism of Cd on biochar changed from precipitation to complexation, and ion exchange processes could be the main reason.

Combination of Biochar and Phosphorus Solubilizing Bacteria to Improve the Stable Form of Toxic Metal Minerals and Microbial Abundance in Lead/Cadmium-Contaminated Soil

Biochar adsorption and microbial remediation have great potential in the field of soil remediation, but since both are stressed by high concentrations of toxic heavy metals when applied alone, combining the two may become an effective remediation method. In this study, the application effect of phosphorus-solubilizing bacteria (PSB) combined with rice husk biochar on the remediation of Pb/Cd-mixed pollution and the form differences of toxic metal were studied qualitatively and quantitatively. Compared with the contaminated soil, the combined remediation of biochar and PSB significantly increased the pH, carbon and phosphorus by 9.0%, 299.4% and 157.0%. Meanwhile, combined remediation increased the total microbial, bacterial and fungal biomass by 92.11%, 103.13% and 138.10%. This confirmed that the addition of biochar increased the soil nutrients and provided good conditions for PSB or native microorganisms to flourish. The extraction results showed that the stable form of Pb/Cd with biochar + PSB was better than that with biochar/PSB alone. Combined remediation significantly increased the acid-soluble and non-bioavailable fraction of Pb/Cd by 5/15 times and 14/5.8 times in contaminated soil. The acid-soluble and non-bioavailable fractions are the main fraction of toxic metals after combined remediation (>80%). The acid-soluble and non-bioavailable fractions were mainly carbonates and phosphate-based Pb/Cd minerals (XRD analysis). PCA and a GWB model further confirmed that the release of pH and phosphorus was the key to the passivation of Pb/Cd in a short time. Meanwhile, the combination of the biochar (phosphorus supply guarantee) and PSB (acid-soluble phosphorus function) can reduce soil acidification and improve soil nutrients, thus increasing microbial abundance in contaminated soil, even more than that in non-contaminated soil.

Joint effects of bacterium and biochar in remediation of antibiotic-heavy metal contaminated soil and responses of resistance gene and microbial community

Soils containing both veterinary antibiotics (VAs) and heavy metals necessitate effective remediation approaches, and microbial and molecular levels of the results should be further examined. Here, a novel material combining waste fungus chaff-based biochar (WFCB) and Herbaspirillum huttiense (HHS1) was established to immobilize copper (Cu) and zinc (Zn) and degrade oxytetracycline (OTC) and enrofloxacin (ENR). Results showed that the combined material exhibited high immobilization of Cu (85.5%) and Zn (64.4%) and great removals of OTC (41.9%) and ENR (40.7%). Resistance genes including tet(PB), tetH, tetR, tetS, tetT, tetM, aacA/aphD, aacC, aadA9, and czcA were reduced. Abundances of potential hosts of antibiotic resistance genes (ARGs) including phylum Proteobacteria and genera Brevundimonas and Rhodanobacter were altered. Total phosphorus and pH were the factors driving the VA degrading microorganisms and potential hosts of ARGs. The combination of WFCB and HHS1 can serve as an important bioresource for immobilizing heavy metals and removing VAs in the contaminated soil.

Prediction of Soil Heavy Metal Immobilization by Biochar Using Machine Learning.

Biochar application is a promising strategy for the remediation of contaminated soil, while ensuring sustainable waste management. Biochar remediation of heavy metal (HM)-contaminated soil primarily depends on the properties of the soil, biochar, and HM. The optimum conditions for HM immobilization in biochar-amended soils are site-specific and vary among studies. Therefore, a generalized approach to predict HM immobilization efficiency in biochar-amended soils is required. This study employs machine learning (ML) approaches to predict the HM immobilization efficiency of biochar in biochar-amended soils. The nitrogen content in the biochar (0.3–25.9%) and biochar application rate (0.5–10%) were the two most significant features affecting HM immobilization. Causal analysis showed that the empirical categories for HM immobilization efficiency, in the order of importance, were biochar properties > experimental conditions > soil properties > HM properties. Therefore, this study presents new insights into the effects of biochar properties and soil properties on HM immobilization. This approach can help determine the optimum conditions for enhanced HM immobilization in biochar-amended soils.

Influence of biochar remediation on Eisenia fetida in Pb-contaminated soils

In this study, the remediation influence of maize straw biochar on earthworms (Eisenia fetida) in contaminated soils (with Pb at 0, 300, 700, and 1000 mg kg−1) amended with different amounts of biochar (0%, 1%, 3%, and 5%) was investigated. The results showed that applying biochar to metal-polluted soils effectively reduced the mobility of Pb, promoting the transformation of Pb from exchangeable (EXC) and bound-to-carbonate (Carb) fractions to Fe/Mn oxide (FeMnOx), organic bound (ORG) and residual (RES) fractions. Consequently, a reduction in the mortality and weight loss of earthworms was also achieved by biochar. The accumulation amount of Pb in earthworms steadily increased with exposure time, and with the increasing dosage of biochar, the accumulated Pb decreased by 50.8–78.0% (300 mg kg−1), 30.9–67.3% (700 mg kg−1), and 17.4–55.1% (1000 mg kg−1), which was significantly positively correlated with the mortality of earthworms. Simultaneously, the application of biochar increased the soil pH (0.05–0.23 units), cation exchange capacity (CEC) (0.26–4.54 cmol kg−1), and content of organic matter (0.54–11.66%). There were higher soil enzyme activities (including sucrase activity, urease activity, and alkaline phosphatase activity) in the treatments with a biochar addition of 3%. Through remediation, Proteobacteria (50.82%), Actinobacteriota (32.37%), Firmicutes (4.83%) and Bacteroidota (1.88%) were the most important phyla in the microbiota communities. Furthermore, soil pH value and leaching toxicity concentration showed the most striking effects on earthworms. Therefore, the influence of earthworms must be taken into account in the remediation of Pb-contaminated soil with biochar.

Effects of modification and co-aging with soils on Cd(II) adsorption behaviors and quantitative mechanisms by biochar.

In this study, original and two KMnO4-modified rice straw biochars (pre- and postmodification) were prepared, which were all pyrolysed at 400°C. Premodified biochar had the largest Cd adsorption capacity, strongest acid and solute buffering capacity, which benefited from the increase of carbonate content, specific surface area, and the emergence of Mn(II) and MnOx through modification. Original and premodified biochars were then conducted four types of aging process by an improved three-layer mesh method, namely, aging without soil and co-aging with acid (pH = 5.00), neutral (pH = 7.00), and alkaline (pH = 8.30) soils. The adsorption capacities of modified biochar were always larger than those of original biochar after aging processes. After four aging processes, Cd(II) adsorption capacities were basically in the order of aged biochar without soil > biochar co-aged with alkaline soil > biochar co-aged with neutral soil > biochar co-aged with acid soil, and KMnO4-modified biochar was always better than original biochar after co-aging with soils. The dominant adsorption mechanism of original and premodified biochars (fresh and aged) for Cd(II) was all the precipitation and adsorption with minerals (accounted for 58.55 ~ 85.55%). In this study, we highlighted that biochar remediation for Cd should be evaluated by co-aging with soil instead of aging without soil participation.

Research on the treatment of heavy metal pollution in urban soil based on biochar technology

Biochar is a material for remediating soil contaminated by heavy metals, and it is also a remediation material for soil improvement. The remediation effect of biochar and its mechanism have been widely concerned in the environmental field. The most important factor that determines the effect of biochar remediation is the diversity of its physical and chemical properties. Cities are extremely important places for human life and production. From a global perspective, the area of cities only occupies less than 2% of the surface area. Urban soil refers to the general term for the original characteristics of the soil in the city or in the suburbs of the city, which are affected to varying degrees by human activities. Therefore, it is very meaningful to study the ecological effects, the chemical migration characteristics of the earth and the sources of heavy metals in urban soils. Based on the current status of heavy metal pollution in urban soils, and at the same time, due to the application potential of biochar in remediation of heavy metal contaminated soil and soil improvement, it is studied to study the effect of 400 °C sludge biochar on heavy metals (Cr, Zn, Cu) The remediation effect of contaminated soil, and at the same time, the raw material sludge is directly used as the remediation material to compare the long-term effects of sludge biochar and sludge on the physical and chemical properties of the soil, the form of heavy metals and the bioavailability, and fully consider The effect of biochar’s aging effect on the repair effect.

Biochar remediation of soil: linking biochar production with function in heavy metal contaminated soils

The focus of this study is on the soil physicochemical, biological, and microbiological processes altered by biochar application to heavy metal (HM) contaminated soils. The aim is to highlight agronomical and environmental issues by which the restorative capacity of biochar might be developed. Literature shows biochar can induce soil remediation, however, it is unclear how soil processes are linked mechanistically to biochar production and if these processes can be manipulated to enhance soil remediation. The literature often fails to contribute to an improved understanding of the mechanisms by which biochar alters soil function. It is clear that factors such as biochar feedstock, pyrolysis conditions, application rate, and soil type are determinants in biochar soil functionality. These factors are developed to enhance our insight into production routes and the benefits of biochar in HM soil remediation. Despite a large number of studies of biochar in soils, there is little understanding of long-term effects, this is particularly true with respect to the use and need for reapplication in soil remediation.

Effect of Water Regimes on Pb and Cd Immobilization by Biochar in Contaminated Paddy Soil

An incubation experiment was conducted to explore the influence of 30% water holding capacity (WHC), flooding, and alternate dry-wet conditions on changes in heavy metal fractions with 1% rice straw biochar in Pb and Cd co-contaminated paddy soils, to provide a scientific basis for a water regime of biochar remediation on heavy metal contaminated paddy soil. Results showed that flooding and alternating wet-dry conditions could significantly increase soil pH, the contents of dissolved organic carbon (DOC), and amorphous iron oxide (Feo) after adding biochar. Compared with a 30% WHC treatment, when the soil is flooded and alternating wet-dry conditions, the content of the TCLP extractable Pb decreased by 31.87% and 20.33%, respectively, and the content of the TCLP extraction Cd decreased by 25.29% and 16.07%, respectively. Under flooding, the acid soluble Pb and Cd content decreased by 24.78% and 20.14%, respectively, and the acid soluble Cd content decreased over time. The decreasing order of available Pb and Cd content was flooding > alternating dry-wet > 30% WHC. Correlation analysis results showed that soil pH and Feo have significant negative correlation with available heavy metals, which means flooding with biochar could effectively immobilize Pb and Cd by increasing soil pH and Feo content. Flooding and biochar have a synergistic interaction on promoting the transformation of Pb and Cd to more stable fractions in acidic co-contaminated heavy metal polluted paddy soil.

Biochar produced from wood waste for soil remediation in Sweden: Carbon sequestration and other environmental impacts.

The use of biochar to stabilize soil contaminants is emerging as a technique for remediation of contaminated soils. In this study, an environmental assessment of systems where biochar produced from wood waste with energy recovery is used for remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAH) and metal(loid)s was performed. Two soil remediation options with biochar (on- and off-site) are considered and compared to landfilling. The assessment combined material and energy flow analysis (MEFA), life cycle assessment (LCA), and substance flow analysis (SFA). The MEFA indicated that on-site remediation can save fuel and backfill material compared to off-site remediation and landfilling. However, the net energy production by pyrolysis of wood waste for biochar production is 38% lower than incineration. The LCA showed that both on-site and off-site remediation with biochar performed better than landfilling in 10 of the 12 environmental impact categories, with on-site remediation performing best. Remediation with biochar provided substantial reductions in climate change impact in the studied context, owing to biochar carbon sequestration being up to 4.5 times larger than direct greenhouse gas emissions from the systems. The two biochar systems showed increased impacts only in ionizing radiation and fossils because of increased electricity consumption for biochar production. They also resulted in increased biomass demand to maintain energy production. The SFA indicated that leaching of PAH from the remediated soil was lower than from landfilled soil. For metal(loid)s, no straightforward conclusion could be made, as biochar had different effects on their leaching and for some elements the results were sensitive to water infiltration assumptions. Hence, the reuse of biocharremediated soils requires further evaluation, with site-specific information. Overall, in Sweden's current context, the biochar remediation technique is an environmentally promising alternative to landfilling worth investigating further.

Research on the adsorption mechanism of Cu and Zn by biochar under freeze-thaw conditions

To investigate the adsorption mechanism of heavy metals by biochar under freeze-thaw conditions, based on indoor simulation experiments, the changes in pH value, surface area (SA), pore structure and functional groups of biochar under natural and freeze-thaw conditions were analysed. Using isothermal adsorption method, Langmuir and Freundlich adsorption equations of heavy metals, the adsorption characteristics of biochar for heavy metals Cu and Zn were analysed. The results showed that after 10 periods (30 cycles), the pH value of the biochar decreased from 8.80 to 7.99, the SA increased from 6.28 m2/g to 20.26 m2/g, the pore volume (PV) decreased from 0.009 mL/g to 0.003 mL/g, and the pore diameter (PD) decreased from 1.692 to 1.423 nm. In period 10, compared to the control group (CK), the adsorption capacity of Cu and Zn increased by 72.00% and 44.55%, respectively, and the number of oxygen-containing functional groups -OH, -COOH and -C=O greatly increased. This study provides scientific and reasonable theoretical guidance for future studies on the biochar adsorption and biochar remediation of soil.

Biochar for sustainable soil management

Biochar for sustainable soil management

Characteristics and Influencing Factors of Microbial Community in Heavy Metal Contaminated Soil under Silicon Fertilizer and Biochar Remediation

Silicon fertilizer and biochar have been widely used to remediate soil contaminated by heavy metals. The effects and mechanism of silicon fertilizer and biochar addition on the heavy metal availability, soil biological properties, and microbial community characteristics need further study in soils contaminated by heavy metals. Therefore, this research determined how silicon fertilizer, biochar, and their combined using affected microbial communities related with nitrogen and phosphorus cycling. The abundance and composition of the microbial community were evaluated by quantitative PCR and phospholipid fatty acid analysis, respectively. Results showed that silicon fertilizer and biochar addition significantly changed soil properties, including pH, total organic carbon, ammonium, nitrate. The Cd and Zn speciation were significantly reduced by silicon fertilizer, biochar, and their integrated application. Microbial community abundance and structure were also significantly changed. Principal component analysis shows that the difference in soil microbial community structure is the most obvious under the combined addition of biochar, silicon fertilizer and biochar. In addition, the results of fluorescence quantitative PCR showed that with biological addition, the number of soil bacteria was significantly reduced. This study reveals the influence of silicon fertilizer and biochar on bacterial and fungal communities in heavy metal soils and the effect of soil heavy metal availability.

Biochar as a potential soil remediation agent for heavy metals in agriculture

Biochar is one of the most concerned research hotspots at present, which is a stable and carbon-rich solid produced by pyrolysis of organic biomass under anoxic conditions. Biochar has abundant pore structure, functional groups, aromatic hydrocarbons and other characteristics, which enable it to improve soil physical and chemical properties, increase nutrient content, and regulate soil microbial community structure. In recent years, with the continuous research on biochar, the role of biochar in the remediation of heavy metal pollution has been further studied. The physical adsorption, ion exchange, electrostatic attraction, complexation reaction, mineral precipitation, redox and other functions of biochar are the main factors for repairing heavy metal ions. In addition, immobilization is the primary goal of biochar remediation of heavy metals in agricultural soils, because it can greatly reduce the risk of human health caused by heavy metals entering the food chain. This paper reviewed the current knowledge of biochar and its function in agricultural heavy metal soil. Based on the background of heavy metal pollution in agricultural soil in China, the possible remediation mechanism of biochar was discussed. It provides scientific basis for the development and application of biochar in the remediation of heavy metal pollution in agricultural soil in China.

Biochar as a potential soil remediation agent for heavy metals in agriculture

Biochar is one of the most concerned research hotspots at present, which is a stable and carbon-rich solid produced by pyrolysis of organic biomass under anoxic conditions. Biochar has abundant pore structure, functional groups, aromatic hydrocarbons and other characteristics, which enable it to improve soil physical and chemical properties, increase nutrient content, and regulate soil microbial community structure. In recent years, with the continuous research on biochar, the role of biochar in the remediation of heavy metal pollution has been further studied. The physical adsorption, ion exchange, electrostatic attraction, complexation reaction, mineral precipitation, redox and other functions of biochar are the main factors for repairing heavy metal ions. In addition, immobilization is the primary goal of biochar remediation of heavy metals in agricultural soils, because it can greatly reduce the risk of human health caused by heavy metals entering the food chain. This paper reviewed the current knowledge of biochar and its function in agricultural heavy metal soil. Based on the background of heavy metal pollution in agricultural soil in China, the possible remediation mechanism of biochar was discussed. It provides scientific basis for the development and application of biochar in the remediation of heavy metal pollution in agricultural soil in China.

Marked Changes in Biochar's Ability to Directly Immobilize Cd in Soil: Implication for Biochar Remediation of Cd Contaminated Soil

To investigate the change in biochar’s ability to directly immobilize Cd in soil，a successive wheat cultivation with experiment was conducted. Three biochar with different Cd adsorption mechanisms were added into soils and a mesh bag was used to separate the soil particles (> 1 μm) from biochar. The results showed that the ash contents and anionic contents (CO3 2- and PO4 3-) of the biochar decreased with the cultivation time, while the oxygen-containing functional groups content and CEC of the biochar increased. Resultly, the Cd concentration on biochar decreased, while unstable Cd species (acid soluble and reducible fraction of Cd) on biochar increased with successive cultivation. Correspondingly, the ability of biochar to inhibit Cd accumulation in wheat decreased. The results of this study illustrated that the ability of biochar to directly immobilize Cd in soil is not permanent, it gradually decreases with aging in soil. The adsorption mechanism of Cd on biochar changed from precipitation to complexation and ion exchange processes could be the main reason.

Development of biochar and activated carbon from cigarettes wastes and their applications in Pb2+ adsorption

This study aimed to transform tobacco from illegal cigarettes into high-efficiency and low-cost adsorbents, and test them in the remediation of lead-contaminated water resources. Biochar and activated carbon were produced by thermal activation technique (originated material CT Biochar) and by thermal, chemical and physical activation techniques (originated material CT ZnCl2 + CO2). Firstly, the materials were characterized by chemical analysis (pHPZC, SEM, FT-IR, BET and BJH). After this, they were submitted to adsorption tests, and to studies aiming the reuse of the adsorbents. The tobacco adsorbents have a surface with tubular structure and spongy aspects, surface functional groups such as alkane, aldehyde, hydroxyl, carboxylic acid, carbonate, alcohol and ether. CT Biochar has a surface area of ​​83.60 m2 g−1 and CT ZnCl2 + CO2 of 46.97 m2 g−1. The optimal Pb2+ adsorption conditions are: solution at pH 5.0, adsorbent dose of 4 g L−1, and time to reach equilibrium of 45 min (CT Biochar) and 10 min (CT ZnCl2 + CO2). The best adjustments were found for pseudo-second order and Langmuir. It was observed that adsorption of Pb2+ occurs in monolayer, and it is predominantly chemical. Estimates regarding costs showed that the production of CT ZnCl2 + CO2 is 0.412 US$ Kg−1, and for CT Biochar is 0.243 US$ Kg−1. Finally, this study provides support for future studies using activated carbons and biochar in remediation of different contaminants, including the use of the adsorbents in larger scales of application, such as wastewater treatment plants.

Remediation of heavy-metal-contaminated soils by biochar: a review

Biochar has seized interest because of its significant effect on the remediation of heavy-metal-contaminated soil. Based on research achievements of biochar remediation of heavy-metal-contaminated ...

Can Addition of Biochar and Zeolite to a Contaminated Calcareous Soil Mitigate the Pb-toxicity Effects on Spinach (Spinacia Oleracea L.) Growth?

ABSTRACT Recently, the use of biochar for remediation of agricultural soils polluted with heavy metals to reduce their toxicity for plants has been expanded. This study aims to evaluate the impact of biochars and zeolite on the biochemical composition of spinach (Spinacia oleracea L.) grown in a Pb-contaminated calcareous soil under greenhouse conditions as completely randomized design. The first factor consists of biochars (without biochar application (CL), green compost (GB), municipal solid waste (MB) and poultry manure (PB) each at 3% (w/w)), and the second factor included zeolite levels (without zeolite application (Z0), 2% (w/w) (Z1) and 4% (w/w) (Z2)). With increasing the zeolite levels, shoot dry matter (3.1 fold), content of chlorophyll a (33.3%), chlorophyll b (37.0%), carotenoids (30.1%), and nutrients uptake (Zn (3 fold), Cu (3.3 fold), Fe (3 fold), Mn (3.7 fold), P (2.9 fold) and K (3.2 fold)) by spinach were significantly enhanced while the enzymes activity (catalase and peroxidase) and Pb concentration (2.9 fold) were reduced significantly. Among the biochars, the MB treatment was the best due to the highest increase in shoot dry matter (57.4%) and nutrients uptake (Zn, Cu, Fe, Mn, P and K) compared to the control. However, it had the lowest Pb concentration and catalase enzyme. Finally, it could be concluded that addition of biochar and zeolite to Pb-polluted calcareous soils can mitigate the Pb-toxicity effects on spinach growth through the reduction of Pb concentration, activity of antioxidant enzymes, and enhancement of the nutrients absorption.