Modified Biochar Research Articles

MgO anchored N-doping biochar enhances the bensulfuron-methyl biodegradation by Acinetobacter YH0317: Higher reactive oxygen species level and bacterial viability

Bensulfuron-methyl (BSM) is a typical broad-spectrum sulfonylurea herbicide and the runoff of BSM residues from agricultural regions poses a significant threat to the ecosystem. Here we develop a bacteria-material hybrid system constructed by Acinetobacter YH0317 and Mg(NO3)2 modified biochar (MBC) for efficiently degrading BSM under various conditions including pH and temperature. Results showed that BSM biodegradation efficiency by YH0317&MBC (96.7 %) was significantly higher than YH0317&BC (79.5 %) and YH0317 (43.9 %) at 15 °C after 7 d of incubation. The addition of MBC significantly increased the reactive oxygen species (ROS) level, which was significantly higher than group YH0317. Moreover, the bacterial viability, extracellular polymeric substances (EPS) production, and membrane permeability of YH0317 were also enhanced with the addition of MBC. The electron paramagnetic resonance (EPR) and quenching experiments revealed that singlet oxygen (1O2) was the dominant active substance produced by MBC. The YH0317&MBC could effectively remove the BSM, and reduce the oxidative stress to soybean, which was beneficial to the growth of soybean through hydroponic experiment. This study establishes a microorganism-material system that efficiently removes BSM in aquatic environments and emphasizes the importance of ROS in pollution removal by the hybrid system.

Synergistic scavenging of sulfamethoxazole and hexavalent chromium in groundwater sample induced by iron-char composites activated persulfate triggering dominant electron transfer process

Effectively scavenging combined pollutants in complex water matrix via dominant electron transfer pathway using modified zero-valent iron (ZVI) remains challenging. Herein, novel iron-based catalysts were synthesized using ball milling and pre-oxidation modified biochar (MOBC), which featured abundant pore structure and oxygen-rich functional moieties to support nZVI in activating persulfate (PS). The most suitable catalytic system achieved ultrafast simultaneous removal of 89.0 % of sulfamethoxazole (SMX) and nearly 100 % of hexavalent chromium (Cr(VI)) within 5 min (with nearly complete removal of SMZ and Cr(VI) in 60 min). By serving as an electron shuttle, MOBC700 could accelerate electron transfer from SMX to PS adsorbed on the nZVI1.0@MOBC700 for SMX decomposition, with reactive oxygen species (ROSs) also contributing. Moreover, nZVI facilitated the reduction of Cr(VI) adsorbed on nZVI1.0@MOBC700 through electron transfer. The dissolved Fe(II) generated via PS activation and Cr(VI) reduction further facilitated Cr(VI) removal from the solution, while the gradual consumption of excess Fe(II) ensured continued ROSs-mediated degradation of SMX. Additionally, the system also demonstrated resistance to interference from NO3-, CO32-, and humic acid, and was effective in remediating four different water samples. Overall, this study presents a promising method for designing iron-char composites to address combined antibiotic and heavy metal contamination in groundwater samples via dominant electron transfer process.

Sulfur Modified Biochar Supported Ferrous Sulfide Composite for the Immobilization of Cadmium in Contaminated Soil

Sulfur Modified Biochar Supported Ferrous Sulfide Composite for the Immobilization of Cadmium in Contaminated Soil

Green catalyst innovation: Enhanced Fischer-Tropsch synthesis using potassium-promoted cobalt catalysts supported on pyrolyzed peanut shells and Cladophora Glomerata modified biochars

This paper explores pyrolysis potential for effective modified biochar (MB) production, serving as a green and novel carbon-based catalyst support in Fischer-Tropsch to olefins synthesis. For this purpose, the MB produced from the pyrolysis of pre-treated Peanut shell (PS) and Cladophora glomerata algae (CG) was used as a high porosity support for cobalt catalyst synthesis. The impregnation technique was applied to prepare the cobalt catalysts, and the catalysts were promoted with potassium. Various methods examine catalysts physico-chemical properties. After 10 h of reduction at 400 °C, the catalysts' activity and selectivity were studied in a fixed-bed reactor. TEM images show that the metal particles are suitably distributed on the porous surface of the modified biochars. The majority of the particles were between 5 and 15 nm in size. Also, TPR results indicate a suitable metal dispersion of about 10% and good catalyst reducibility have been achieved. The cobalt catalysts produced on MBs of CG and PS exhibited FT rates of 0.245 and 0.223 (g HC/g cat.h), with CO conversion rates of 50.25% and 45.68% in each case. Finally, K-promoted cobalt catalysts supported on MBs of CG and PS showed the α-olefins selectivities of 38.67% and 35.49% for C2-C13 hydrocarbons, respectively.

Mechanism of Cd Adsorption by Sulphur Modified Biochar and Its Application in Cd-Contaminated Soil

Mechanism of Cd Adsorption by Sulphur Modified Biochar and Its Application in Cd-Contaminated Soil

The Impact of Phosphate Solubilizing Bacteria Modified Biochar on Maize Seedling Growth and Rhizosphere Phosphate Availability

The Impact of Phosphate Solubilizing Bacteria Modified Biochar on Maize Seedling Growth and Rhizosphere Phosphate Availability

Activated persulfate by the synergistic electro-activation and bimetals cathode (MBC@CF) leads to highly efficient degradation of tetracycline

This study established an efficient coupled activation persulfate (PMS) process with a bimetallic modified biochar (MBC)-loaded cathode (MBC@CF) as the main body to remove tetracycline (TC) by electric field-enhanced catalytic cathodic activation of PMS (E-MBC@CF-PMS). The synergistic effect of electrocatalytic co-activation in the E-MBC@CF-PMS system (5.54) was two to three times higher than the electrically activated (2.39) / electro-catalytic (2.03) systems. The fundamental reason is that the presence of electric field enhances the efficient activation of PMS at sites like C = O and Metal-N-C (M−N−C) on the catalytic cathode surface and makes it easier for the vital element Mn+ in the ligand structure to regenerate. 1O2 generated during electrocatalytic co-activation and electron transfer was demonstrated to dominate in the efficient removal of pollutants using free radical quenching and electron spin resonance. This study offers a fresh idea to encourage the effective and practical activation of PMS.

Adsorption recovery of phosphorus in contaminated water by calcium modified biochar derived from spent coffee grounds

Phosphate recovery from water is essential for reducing water eutrophication and alleviating the phosphorus resource crisis. In this study, spent coffee grounds and CaCl2 were used as raw materials and a modifier, respectively, to create a novel calcium modified biochar (MBC) for removing phosphorus from water. The modified biochar (MBC) was the best at removing phosphorous when the modifier concentration was 1.5 M with theoretically maximum adsorption capacity of 70.26 mg/g. MBC also performed well in the wide pH range of 3–11 under different phosphorus concentration gradients, with phosphorus removal efficiency of more than 50 %. According to kinetic analysis, the adsorption process at low phosphorus concentrations (50–100 mg/L) can be more properly described by the pseudo-first-order model, while the pseudo-second-order model best describes the adsorption process at high concentrations (200–600 mg/L). The thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. Characterization results revealed that surface precipitation, complexation, and ligand exchange were the dominant mechanisms of phosphorus adsorption. MBC has great potential to recover phosphorus from wastewater.

Management of agricultural waste to manufacture biochar: An alternative reinforcing filler for carbon black in nitrile butadiene rubber composites

The carbon black (CB) used in rubber manufacturing and the unsafe disposal of agricultural waste are one of the causes of environmental pollution. Indeed, the production of one ton of CB produces about 2.4 tons of carbon dioxide. The conversion of these agricultural wastes into biochar (Bi) and using them as a reinforcing material is one of the trends that achieve sustainability and promote environmentally sound. Herein, the modified biochar (MBi) was obtained by chemo-mechanical treatment utilizing stearic acid for Bi which was produced from the pyrolysis of citrus trees to enhance its dispersion in nitrile butadiene rubber (NBR) composite. In addition, the present study scrutinized the influence of synergism between the MBi and CB as a filler in the NBR composites. The characterization of as-prepared samples was carried out by tracing the surface morphology, particle size analyzer, and identification of chemical bonds, as well as rheological, mechanical, aging, and electrical conductivity properties. The rheological studies showed that the optimum vulcanization time (tc90) did not significantly prolong for MBi-filled composites, which sequentially higher the benefits of the study by reducing energy consumed and thus, the process cost. In addition, the surface morphology and the mechanical data have distinguished that MBi particles were well-distributed along the matrix, as revealed by the tensile properties of the final composites. The electrical conductivity results manifested that MBi did not adversely affect the enhancement of conductivity. Whereas, the permittivity was increased due to the interfacial polarization between the filler and rubber matrix. In conclusion, the innovative filled-MBi elastomer composite would pave the way for an eco-friendly product that is valid for various applications.

Exploring biochar and fishpond sediments potential to change soil phosphorus fractions and availability.

Phosphorus (P) availability in soil is paradoxical, with a significant portion of applied P accumulating in the soil, potentially affecting plant production. The impact of biochar (BR) and fishpond sediments (FPS) as fertilizers on P fixation remains unclear. This study aimed to determine the optimal ratio of BR, modified biochar (MBR), and FPS as fertilizer replacements. A pot experiment with maize evaluated the transformation of P into inorganic (Pi) and organic (Po) fractions and their contribution to P uptake. Different percentages of FPS, BR, and MBR were applied as treatments (T1-T7), T1 [(0.0)], T2 [FPS (25.0%)], T3 [FPS (25.0%) + BR (1%)], T [FPS (25%) +MBR (3%)], T5 [FPS (35%)], T6 [FPS (35%) +BR (1%)], and T7 [FPS (35%) + MBR (1%)]. Using the modified Hedley method and the Tiessen and Moir fractionation scheme, P fractions were determined. Results showed that various rates of MBR, BR, and FPS significantly increased labile and moderately labile P fractions (NaHCO3-Pi, NaHCO3-Po, HClD-Pi, and HClC-Pi) and residual P fractions compared with the control (T1). Positive correlations were observed between P uptake, phosphatase enzyme activity, and NaHCO3-Pi. Maximum P uptake and phosphatase activity were observed in T6 and T7 treatments. The addition of BR, MBR, and FPS increased Po fractions. Unlike the decline in NaOH-Po fraction, NaHCO3-Po and HClc-Po fractions increased. All Pi fractions, particularly apatite (HClD-Pi), increased across the T1-T7 treatments. HClD-Pi was the largest contributor to total P (40.7%) and can convert into accessible P over time. The T5 treatment showed a 0.88% rise in residual P. HClD-Pi and residual P fractions positively correlated with P uptake, phosphatase activity, NaOH-Pi, and NaOH-Po moderately available fractions. Regression analysis revealed that higher concentrations of metals such as Ca, Zn, and Cr significantly decreased labile organic and inorganic P fractions (NaHCO3-Pi, R 2=0.13, 0.36, 0.09) and their availability (NaHCO3-Po, R 2=0.01, 0.03, 0.25). Excessive solo BR amendments did not consistently increase P availability, but optimal simple and MBR increased residual P contents in moderately labile and labile forms (including NaOH-Pi, NaHCO3-Pi, and HClD-Pi). Overall, our findings suggest that the co-addition of BR and FPS can enhance soil P availability via increasing the activity of phosphatase enzyme, thereby enhancing plant P uptake and use efficiency, which eventually maintains the provision of ecosystem functions and services.

Study on Adsorption of Phosphate in Water Environment by Mg–Al Modified Biochar

Excessive release of phosphate has gained prominence as a pivotal contributor to water contamination. Biochar, known for its abundant surface acreage and unparalleled adsorptive prowess, has been widely employed in aqueous remediation. Within the scope of this investigation, unprocessed biochar was derived from Chaetomorpha valida via pyrolysis methodologies involving temperatures ranging from 320 °C, 460 °C, 620 °C, and 860 °C, respectively. Mg-BC620, Al-BC620, and Mg–Al-BC620 were prepared using the co-precipitation method at the optimal temperature to maximize the resource utilization of Chaetomorpha valida. The physicochemical attributes of altered biochars were evaluated employing X-ray diffractometry and other analytical techniques. The influence of different factors on phosphate’s adsorptive aptitude of altered biochar was investigated, and the adsorptive behavior and mechanism of biochar were studied using diverse kinetics of adsorption and assortment of isotherm models. The outcomes revealed that the optimal pyrolysis temperature was 620 °C, and the altered biochar displayed a strikingly elevated affinity for phosphate sorption, outperforming the unaltered biochar. Among the modified biochars, Mg–Al-BC620 outperformed the rest, boasting an astonishing eradication rate of 94.92% when dosed at 8 g/L, maintaining a pH equilibrium of 7 in the solution, while confronting an inceptive phosphate density of 150 mg/L. The utmost threshold of adsorption proficiency predicted by the Langmuir equation was 228.130 mg/g, which was 88.56 times that of BC620. This modified biochar exhibits a strong affinity for phosphate and excellent adsorption selectivity, providing a promising avenue for the resource utilization of Chaetomorpha valida and has broad application prospects for scavenging phosphate in aqueous mediums.

Nutrient Recovery from Poultry Wastewater by Modified Biochar: An Optimization Study

In this work, we proposed and tested a method for utilizing agricultural waste and alum sludge as an effective adsorbent to treat poultry wastewater. The product was also targeted to be used as fertilizer for agriculture. Modified biochar was produced from crop residues, sludge from a water treatment plant, and magnesium salt. The produced biochar was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller analysis, and X-ray diffraction. The adsorption of ammonia and phosphate in both synthetic and actual poultry wastewater by the produced biochar was conducted. The effect of experimental conditions such as N to P ratio, initial concentrations of ammonium and phosphate, pH, and the amount of biochar on the adsorption capacity for ammonia and phosphate were also investigated. The results from the experiment showed that the best adsorption capacities were 60.64 mgNH4+-N/g and 66.24 mgPO43--P/g, which were produced at the optimum conditions of N to P ratio of 1.25, initial concentration of 90 mg/L, pH 6, and biochar mass of 0.105 g. These results create an opportunity for the effective production of slow-release fertilizer from crop residues and alum sludge for ecological agriculture in the future.

The simultaneous high-effective removal of As(III) and Cd by a modified biochar derived from rice straw

The highly-effective removal of arsenic (As) and cadmium (Cd) at the same time has always been a hot and challenging topic in the world. This experiment was designed to study the removal efficiency and mechanisms of the potassium permanganate (KMnO4) modified biochar (MBC) on As(III) and Cd. The results indicated that the maximum sorption capacities of As and Cd by MBC were 141.1 and 224.4 mg/g in As(III)-Cd coexisting solution at pH 7, which were significantly higher than that in a single As(III) or Cd solution (75.0 and 122.1 mg/g, respectively). The formation of type-A ternary complex (MBC-Cd-As) and type-B ternary complex (MBC-As-Cd) in high Cd concentration (>150 mg/L) were the predominant synergy mechanisms for MBC to remove As and Cd, respectively. Moreover, the Cd reacted mainly electrostatic adsorption and π-π interactions with the aromatic complexes on the MBC surface. The As mainly reacted with the MnO2 and the oxidation of As(III) to As(V) was also accompanied by the sorption by MBC. In general, MBC is a highly-effective material to remove As(III) and Cd simultaneously from contaminated water.

Pretreatment of Biogas Slurry by Modified Biochars to Promote High-Value Treatment of Wastewater by Microalgae

High concentrations of contaminants such as ammonia nitrogen and organic matter in full-strength wastewater severely inhibit the growth of microalgae, contributing to lower biomass accumulation and contaminant removal efficiency. To overcome this limitation, modified biochars prepared from pine sawdust and sugarcane bagasse were used in this study as an adsorbent–desorbent for the pretreatment of wastewater to promote the growth of microalgae. The results showed that the two modification methods (acid/alkaline modification and magnesium salt modification) used in the experiment could increase the abundance of oxygen-containing functional groups. Moreover, magnesium salt modification could effectively improve the pore structure of biochar surfaces and increase the specific surface areas. Compared with the pristine biochars, the adsorption performance of the modified biochar was found to be significantly higher for nutrients in wastewater. The adsorption capacity of the acid/alkaline-modified pine sawdust biochar reached 8.5 and 16.49 mg∙g−1 for ammonia nitrogen and total organic carbon in wastewater, respectively. The magnesium salt modified pine sawdust biochar achieved a more comprehensive nutrients adsorption capacity of 15.68, 14.39, and 3.68 mg∙L−1 for ammonia nitrogen, total organic carbon, and total phosphorus, respectively. The mechanism of ammonia nitrogen adsorption was mainly the complexation of surface -OH functional groups, while the adsorption mechanism for phosphate was mainly the complexation of -OH and Mg-O functional groups and the chemical precipitation of MgO or Mg(OH)2 attached to the surface.

Citric acid modified biochar application at a low dosage can synchronically mitigate the nitrogenous gas pollutants emission from rice paddy soils

Raw biochar with high pH possibly stimulated ammonia (NH3) volatilization in the agricultural soil. We hypothesized that the modified biochar (MBC) with low pH can synchronically decrease the NH3 and nitrous oxide (N2O) losses. We performed a two-year experiment to clarify how citric acid MBC influence the NH3 volatilization and N2O emission as well as the underlying mechanisms. Two typical paddy soils, i.e., Hydragric Anthrosol and Haplic Acrisol, receiving equal urea N with 240 kg ha−1 but varied rates of MBC with 0, 5, 10, and 20 t ha−1 (named Urea, Urea + MBC5, Urea + MBC10, and Urea + MBC20, respectively) were studied. The results showed that MBC-amended treatments effectively mitigated the NH3 volatilization from Hydragric Anthrosol and Haplic Acrisol by 29.6%–57.9% and 30.5%–62.4% in 2017, and by 16.5%–21.0% and 24.5%–35.0% in 2018, respectively, compared to Urea treatment. In addition, significantly lower N2O emissions with averaged 38.3% and 43.1% in 2017, and 51.7% and 26.7% were recorded under Hydragric Anthrosol and Haplic Acrisol, respectively, following the MBC application (P < 0.05). Increased MBC addition performed higher efficacy on mitigating NH3 volatilization, particularly in the first rice season, while this “dosage effect” was not found for N2O reduction. Lowered pH in overlying water, enhanced adsorption of NH4+-N and its nitrification rate likely contributed to the lower NH3 volatilization as result of MBC addition. The nirS and nosZ gene copies were not changed by MBC, while the nirK gene copies were decreased as result of MBC amendment by 8.3%–25.2% under Hydragric Anthrosol and by 21.8%–24.9% under Haplic Acrisol. Consequent lower ratio of nirK/(nirS + nosZ) explained the mitigation effect of MBC on N2O emission. In conclusion, the present two-year study recommends that MBC applied at a low dosage can perform positive effect on controlling the nitrogenous gas pollutants from paddy soil.

Alginate-modified biochar derived from rice husk waste for improvement uptake performance of lead in wastewater

In this work, alginate-modified biochar derived from rice husk waste was synthesized using a simple process. The modified biochar (MBC) and rice husk biochar (RhBC) were investigated for removing Pb (II) ions in wastewater. The BET result displayed significantly improved specific surface area of MBC up to 120 m2/g along with a total pore volume of 0.653 cm3/g. FTIR spectrums presented the higher oxygen-contained functional groups of MBC as compared to RhBC, resulting in increasing adsorption capacity of Pb (II). MBC had higher adsorption capacity (112.3 mg/g) and faster removal rate (0.0081 g mg−1 min−1) than those of RhBC (41.2 mg/g and 0.00025 g mg−1 min−1). Modified RhBC can remove more than 99% of Pb (II) from wastewater and it could be utilized for three cycles with a removal performance of over 90%. In addition, the Pb adsorption mechanism by using MBC was proposed and the practical application of MBC for the treatment of wastewater in Vietnam was discussed.

Fabrication of Nano Iron Oxide-Modified Biochar from Co-Hydrothermal Carbonization of Microalgae and Fe(II) Salt for Efficient Removal of Rhodamine B.

Dye adsorption by magnetic modified biochar has now received growing interest due to its excellent adsorption performance and facile separation for recycling. In this study, nano iron oxide–modified biochar was fabricated via the successive hydrothermal-pyrolyzing method using Chlorella vulgaris (Cv) and FeSO4·7H2O as raw materials, and its adsorption on Rhodamine B (RhB) in aqueous solution was studied. Multiple techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) were employed to comprehensively characterize the structure, morphology and physicochemical properties of the adsorbent. The as-synthesized nano iron oxide–modified biochar (CBC-Fe(II)) exhibited a large surface area (527.6 m2/g) and high magnetic saturation value (13.7 emu/g) to facilitate magnetic separation. Compared with CBC and CBC-Fe(III), CBC-Fe(II) exhibited superior adsorption ability towards RhB in aqueous solution, with a maximum adsorption capacity of 286.4 mg/g. The adsorption process of RhB onto CBC-Fe(II) was well described by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating monolayer chemisorption behaviors for the adsorption system. Facile preparation, great adsorption performance and magnetic recovery properties endow CBC-Fe(II) to be a promising adsorbent for dye removal.

Reactive blue 19 adsorption behaviors of magnesium hydroxide modified biochar derived from the traditional Chinese medical residual

This study examined the reactive blue 19 (RB-19) adsorption behaviors of magnesium hydroxide modified biochar (MBC) derived from the traditional Chinese medical residual. The obtained MBC was characterized using Scanning Electron Microscope (SEM), Fourier Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET). The static adsorption experiment was carried out to investigate the adsorption properties. The results indicated that pH 4 was best for the adsorption removal of RB-19 in the pH range of 4–9. Compared with the pseudo-first-order model and Elovich model, the pseudo-second-order equation was best to describe the adsorption process (R2 > 0.995). The Langmuir model was better than the Freundlich model to fit the experimental data (R2 > 0.990). The intra-particle diffusion model showed that film diffusion and intra-particle diffusion were involved in the adsorption process. Thermodynamic parameters showed that the RB-19 adsorption by MBC was spontaneous and endothermic. The adsorption mechanism might include electrostatic interaction, pore filling, and hydrogen bond, and the MBC was a promising adsorbent.

Heavy Metal Remediation from Contaminated Soil Using Biochars and Modified Biochars: A Review

From the beginning of the industrial revolution, metal refining industries using the pyrometallurgical process are generating remarkable emissions of heavy metals. As the main objective of these pollutants, a great number of soils are now contaminated over extensive areas depending on exposure level, and duration, and pose a major risk to human health worldwide. Biochar, a co-product of the pyrolysis process, can be used to nourish soil health, and remediate heavy metals. They are nowadays modified to enhance the sorption capacity of biochar and immobilization of heavy metals. Immobilization, as an in-situ application method, is a cost-effective method for environmental remediation of heavy metals in the soils. The research statistics on biochar and modified biochar influences on heavy metal remediation from the soil are scarce. Therefore, the purposes of this review are (1) to combine modification processes of biochar (2) to offer possible mechanisms associated with the reduction of heavy metals (iii) to combine the available data on the positive effects of biochars and modified biochars on heavy metal remediation(iv) identify researchable priorities.

Effects of Earthworms/Biochar on Bacterial Diversity and Community in As-contaminated Red Soil

Cerium-manganese modified biochar (MBC) combined with earthworms (Eisenia foetida) can immobilize arsenic (As) in red soils. In this study, high-throughput sequencing technology was used to explore the combined effects of MBC and E. foetida on bacterial diversity and community structure in As-contaminated red soils. The results showed that the single earthworm treatment had the highest diversity index, whereas the diversity index decreased in the single biochar or MBC treatment, indicating that earthworms can boost the growth of bacteria in the soil, and the addition of biochar/MBC all decreased the bacterial diversity of soils. When biochar/MBC was combined with earthworms, the diversity index increased to some degree. In terms of bacterial community structure, the relative abundance of Proteobacteria and Bacteroidetes increased significantly in each treatment, especially for MBC-earthworm treated soil, in which the relative abundance was increased by 17.08% and 329.47% for Proteobacteria and Bacteroidetes, respectively, compared to that in the control (CK). Otherwise, those abundances were decreased by 19.18% and 48.76%, respectively, for Acidobacteria and Chloroflexi. Correlation analysis results showed that the soil water-soluble As (WSAs) was negatively correlated with the relative abundances of Proteobacteria and Bacteroides (P<0.05) but was positively correlated with Acidobacteria and Chloroflexi (P<0.05), which indicated that with the decrease in WSAs in soils, the bacteria of Proteobacteria and Bacteroides reproduced rapidly, whereas the Acidobacteria and Chloroflexi were inhibited. Moreover, different treatments induced selective changes in the bacterial community, in which earthworms significantly promoted the proliferation of γ-Proteobacteria, Flavobacteriales, Aeromonadales, and Variovorax and earthworms improved the immobilization effect of As by promoting the growth of these bacteria.