Biochar Pyrolysis Temperature Research Articles

Insights into CO2 and N2O emissions driven by applying biochar and nitrogen fertilizers in upland soil

Biochar and soil carbon sequestration hold promise in mitigating global warming by storing carbon in the soil. However, the interaction between biochar properties, soil carbon-nitrogen cycling, and nitrogen fertilizer application's impact on soil carbon-nitrogen balance remains unclear. Herein, we conducted batch experiments to study the effects and mechanisms of rice straw biochar application (produced at 300, 500, and 700 °C) on net greenhouse gas emissions (CO2, N2O, CH4) in upland soils under different forms of nitrogen fertilizers. The findings revealed that (NH4)2SO4 and urea significantly elevated soil carbon dioxide equivalent emissions, ranging from 28 to 61.7 kg CO2e/ha and 8.2 to 37.7 kg CO2e/ha, respectively. Conversely, KNO3 reduced soil CO2e emissions, ranging from 2.2 to 13.6 kg CO2e/ha. However, none of these three nitrogen forms exhibited a significant effect on CH4 emissions. The pyrolysis temperature of biochar was found negatively correlated with soil CO2 and N2O emissions. The alkaline substances present in biochar pyrolyzed at 500–700 °C raise soil pH, increase the ratio of Gram-negative to Gram-positive bacteria, and enhance the relative abundance of Sphingomonadaceae. Moreover, the co-application of KNO3 based nitrogen fertilizer and biochar increases the total carbon/inorganic nitrogen ratio and reduces the relative abundance of Nitrospirae. This series of reactions lead to a significant increase in soil DOC content, meanwhile reduces soil CO2 emissions, and inhibits the nitrification process and decreases the emission of soil N2O. This study provides a scientific basis for the rational application of biochar in soil.

Redox conditions and biochar pyrolysis temperature affecting As and Pb biogeochemical cycles and bacterial community of sediment from mining tailings

Despite the widespread use of biochar for soil and sediment remediation, little is known about the impact of pyrolysis temperature on the biogeochemistry of arsenic (As) and lead (Pb) and microorganisms in sediment under reducing conditions. In this study, we investigated the effects of pyrolysis temperature and the addition of glucose on the release and transformation of As and Pb, as well as their potential effects on the bacterial community in contaminated sediments. The addition of biochar altered the geochemical cycle of As, as it favors specific bacterial groups capable of changing species from As(V) to As(III) through fermentation, sulfate respiration and nitrate reduction. The carbon quality and content of N and S in solution shaped the pH and redox potential in a way that changed the microbial community, favoring Firmicutes and reducing Proteobacteria. This change played a fundamental role in the reductive dissolution of As and Pb minerals. The addition of biochar was the only efficient way to remove Pb, possibly as a function of its sorption and precipitation mechanisms. Such insights could contribute to the production or choice of high-efficiency biochar for the remediation of sediments subjected to redox conditions.

Enhancing boreal forest resilience: A four-year impact of biochar on soil quality and fungal communities

Boreal forests commonly suffer from nutrient deficiency due to restricted biological activity and decomposition. Biochar has been used as a promising strategy to improve soil quality, yet its impacts on forest soil microbes, particularly in cold environment, remains poorly understood. In this study, we investigated the effects of biochar, produced at different pyrolysis temperatures (500 °C and 650 °C) and applied at different amounts (0.5 kg·m−2 and 1.0 kg·m−2), on soil property, soil enzyme activity, and fungal community dynamics in a boreal forest over a span of two to four years. Our results showed that, four-year post-application of biochar produced at 650 °C and applied at 1.0 kg·m−2, significantly increased the relative abundance of Mortierellomycota and enhanced fungal species richness, α-diversity and evenness compared to the control (CK) (P < 0.05). Notably, the abundance of Phialocephala fortinii increased with the application of biochar produced at 500 °C and applied at 0.5 kg·m−2, exhibiting a positively correlation with the carbon cycling-related enzyme β-cellobiosidase. Functionally, distinct fungal gene structures were formed between different biochar pyrolysis temperatures, and between application amounts in four-year post-biochar application (P < 0.05). Additionally, correlation analyses revealed the significance of the duration post-biochar application on the soil properties, soil extracellular enzymes, soil fungal dominant phyla, fungal community and gene structures (P < 0.01). The interaction between biochar pyrolysis temperature and application amount significantly influenced fungal α-diversity (P < 0.01). Overall, these findings provide theoretical insights and practical application for biochar as soil amendment in boreal forest ecosystems.

The Effect of Pyrolysis Temperature of calotropis procera Biochar on Dynamics of Petroleum Hydrocarbons Degradation, Carbon Emission, and Ammonia Volatilization in Artificial Petroleum-Contaminated Soil

AbstractPollution by petroleum hydrocarbons (PHCs) is a current environmental challenge all over the world. Therefore, this study was established to evaluate the impact of calotropis procera biochar (CPB) produced at various pyrolysis temperatures on carbon emission, ammonia volatilization, degradation of PHCs, and properties of artificial petroleum-contaminated soil. An incubation experiment was performed with CPB produced at 400 °C (CPB400) and 650 °C (CPB650). The artificial petroleum-contaminated soil was amended with biochar at doses of 1, 2.5, and 5% along with the unamended soil (control) and incubated for 78 days. The results demonstrate that the CO2-C emission rate in petroleum-contaminated soil increases significantly with all biochar applications compared to the control treatment. Adding CPB400 into the soil, at all doses, decreased cumulative NH3 emission significantly, in comparison with control and CPB650 treatments during all incubation periods. Total PHCs concentration in the soil reduced significantly with CPB400 application at 2.5% compared to the control treatment. CPB400 was more effective in declining total PHCs content in the soil than biochar produced at 650 °C. Available phosphorus and potassium in petroleum-contaminated soil increased significantly under biochar applications compared with the control treatment. Using Calotropis procera biochar produced by low-temperature pyrolysis as an amendment can play a vital role in the remediation of PHCs in polluted soils, it is also a promising way to improve the quality indicators of petroleum-contaminated soil.

Role of biochar pyrolysis temperature on intracellular and extracellular biodegradation of biochar-adsorbed organic compounds

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5–47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8–60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4–92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H2O2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H2O2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation.

Effects of biochar pyrolysis temperature on uranium immobilization in soil remediation: Revealed by 16S rDNA and metabolomic analyses

Uranium-stressed soil caused by nuclear industry development and energy acquisition have attracted extensive attentions for a long time. This study investigated the effects of biochar application with different pyrolysis temperatures (300 ℃, 500 ℃ and 700 ℃) on remediation of uranium-stressed soil. The results showed that higher pyrolysis temperature (700 ℃) was benefit for ryegrass growing and caused a lower uranium accumulation in plants. At the same time, uranium immobilization was more effective at higher biochar pyrolysis temperature. Careful investigations indicated that activities of soil urease and sucrase were promoted, and bacterial diversity was strengthened in C700 group, which may contribute to uranium immobilization. The biochar application could activate metabolic of lipids and amino acids, organic acids and derivatives, and organic oxygen compounds. Nicotinate and nicotinamide metabolism, and Benzoxazinoid biosynthesis were unique metabolic pathways in the C700 group, which could enhance the uranium tolerance from different perspectives. Based on these results, we recommend to use biochar with 700 °C pyrolysis temperature when processing remediation of uranium-stressed soil. This study will facilitate the implementation of biochar screening and provide theoretical helps for remediation of uranium-stressed soil.

Inactivation of harmful cyanobacteria Microcystis aeruginosa by Cu2+ doped corn stalk biochar treated with different pyrolysis temperatures

In this study, biochars (BCs) derived from corn stalk treated at various pyrolysis temperatures (350–950 °C) were prepared and then loaded with Cu2+ to form highly efficient algaecide, i.e. Cu2+-doped BC composites (Cu-BCs). The results showed BCs pyrolyzed at higher temperatures suppressed the growth of Microcystis aeruginosa in the order of BC550 ≫ BC750 > BC950, while BC350 accelerated cell growth due to the release of inorganic nutrients. The difference could be attributed to the physicochemical characteristics, including specific surface area, adsorption capacity of nutrients and the presence of particularly persistent free radicals. Furthermore, Cu-BCs exhibited the improved inactivation performance, but the 72 h growth inhibition rates and reaction activities of Cu-BCs were still influenced by the Cu2+ loading ratio and pyrolysis temperature. These results, reported for the first time, demonstrated the algae inactivation efficiency of pristine BCs, and Cu-BCs were principally manipulated by the biochar pyrolysis temperature.

Biochar enhances microbial degradation of phenol in water: Response surface optimization

The utilization of biochar-immobilized microorganisms is an effective method for eliminating phenol from water. However, the main challenge to the practical implementation of this method is the high susceptibility of bacteria to environmental factors. In this study, biochar was used to reduce microbial susceptibility to high concentrations of phenol. Demineralized biochar obtained at high temperatures (600/800/1000 °C) was used to immobilize phenol-degrading bacteria (PDB) and enhance phenol removal. Biodegradation was inhibited by high concentrations of phenol (>1300 mg/L). In contrast, when microorganisms were combined with biochar, up to 82.4% phenol removal occurred, surpassing the efficacy of phenol degradation by a single microorganism (42%). Characterization techniques such as SEM, XRD, and XPS were used to analyze the properties and immobilization effect of biochar. The addition of biochar altered the dominant species of PDB to include Serratia, Ralstonia and Enterobacter. Response surface analysis indicated that both biochar pyrolysis temperature and experimental temperature significantly influenced the phenol removal rate. Thus, this paper provides methodological guidance for the application of biochar-immobilized microorganisms for phenol wastewater treatment.

Effect of municipal sludge-based biochar produced at different pyrolysis temperatures on humification and oxytetracycline degradation of pig manure composting

This study explored the influence of pyrolysis temperatures on the properties of municipal sludge-based biochar (MSB) and evaluated the impact of MSB on humification and oxytetracycline (OTC, a broad-spectrum antibiotic) degradation in pig manure composting. Three types of MSB were produced from sewage sludge pyrolyzed at 300 °C, 500 °C, and 700 °C, respectively. Results indicated that pyrolysis temperature adjusted the formation sequence of the functional groups in MSB, and higher pyrolysis temperatures enriched the aromaticity of the biochar and augmented the concentrations of humic precursor compounds. The MSB addition to pig manure composting enhanced the peak temperature and prolonged the thermophilic phase. Moreover, the MSB addition significantly increased the HI (humic acid/fulvic acid) values (1.6–2.57) compared with the control (1.28), with a more pronounced effect observed at higher biochar pyrolysis temperatures. Furthermore, the MSB reduced the half-life of OTC degradation (1.47–2.44 d) during composting, accelerating its degradation compared with the control (2.66 d). The study demonstrated that the MSB provided a substantial amount of humic precursor materials into the composting process while also expediting the degradation of organic matter, thereby enhancing the humification process. Moreover, the extended duration of the thermophilic phase accelerated the degradation of OTC and shortened its half-life. Notably, the MSB at 700 °C had the best performance compared with other MSBs.

Review of Photochemical Activity of Dissolved Black Carbon in Aquatic Environments: Primary Influencing Factors and Mechanisms

Dissolved black carbon (DBC), the particular component of black carbon that can be dissolved in the water, which accounts for ~10% of the organic carbon cycle in the earth’s water body, is an essential member of the dissolved organic matter (DOM) pool. In contrast to DOM, DBC has a higher proportion of conjugated benzene rings, which can more efficiently encourage the degradation of organic micropollutants in the aquatic environment or more rapidly generate reactive oxygen species to photodegrade the organic micropollutants. Therefore, it is of great significance to study the changes and mechanisms of DBC photochemical activity affected by different factors in the water environment. Our work reviewed the main influencing factors and mechanisms of the photochemical activity of DBC. It focuses on the methodologies for the quantitative and qualitative investigation of the photochemical activity of DBC, the impact of the biomass source, the pyrolysis temperature of biochar, and the primary water environmental parameters on the photochemical activity of DBC and the indirect photodegradation of pollutants. Based on this, a potential future study of DBC photochemical activity has been prospected.

Effect of Mg-Modified Waste Straw Biochar on the Chemical and Biological Properties of Acidic Soils.

Biochar is important for soil improvement, fertilizer innovation, and greenhouse gas reduction. In this paper, Mg-modified biochar was prepared from rice and corn straw and mixed with soil at a 1% (w/w) addition in an indoor soil simulation experiment to study the effect of Mg-modified biochar on the chemical properties of acidic soil. The results showed that the addition of Mg-modified biochar reduced soil acidity and improved soil fertility. Compared with the control group, the Mg-modified biochar treatment significantly increased the concentrations of available potassium, available phosphorus, total phosphorus, organic carbon and exchangeable calcium and magnesium in the soil, and effectively increased the concentration of total nitrogen. Rice straw Mg-modified biochar treatment was more effective in increasing the soil-available potassium, available phosphorus, total phosphorus and exchangeable magnesium concentration, while corn straw Mg-modified biochar was more effective in increasing the soil organic carbon and exchangeable calcium concentration. In addition, the high pyrolysis temperature of Mg-modified biochar was more effective in promoting the soil-available potassium, available phosphorus and total nitrogen concentration, while the low pyrolysis temperature of Mg-modified biochar was more effective in promoting soil alkaline nitrogen, exchangeable calcium and magnesium.

Poplar Sawdust Biochar Altered Community Composition of Dominant Soil Fungi but Not Bacteria Depending on Pyrolysis Temperature

There is a growing focus on the production of biochar from organic wastes and its forestry use. However, it is unclear how applying biochar pyrolyzed at different temperatures influences both soil bacterial and fungal communities. In this study, two kinds of biochar were pyrolyzed at 350 °C and 600 °C, from poplar sawdust, and then applied as an auxiliary substrate material (15% addition by volume) for the container seedling cultivation of Cyclocarya paliurus, a native timber and medically used tree species, to compare the response of the soil’s microbial traits. The results showed that after 5 months of cultivation, the addition of the biochar application improved the soil’s physical and chemical properties to a certain extent by decreasing its bulk density and increasing its field water-holding capacity, pH and organic carbon content. The soil’s pH and content of organic C, available N and available P were significantly higher in the substrate with the addition of the biochar pyrolyzed at 600 °C (Bioc600) than in that of the substrate with added pyrolyzed biochar at 350 °C (Bioc350). The biochar application also enhanced the soil’s microbial N (MBN) but showed no changes in the MBC/MBN ratio. The biochar application had no effect on the diversity and composition of the soil’s bacterial community, but showed a certain effect on its fungal community composition and had different influences between low and high pyrolysis temperatures. The relative abundance of several of the dominant fungal phyla and genera increased with the addition of biochar due to the increase in the soil’s pH when compared to the CK (no biochar or sawdust addition). When compared with Bioc350, the dominant phylum Basidiomycota and genus Vanrija further increased in abundance with Bioc600. These findings reveal the consistent effects of biochar pyrolysis temperature and demonstrate the different regulatory roles of biochar application in soil bacterial and fungal communities, providing valuable information on how biochar can effectively be used as a substrate for seedling cultivation.

Predicting the speciation of ionizable antibiotic ciprofloxacin by biochars with varying carbonization degrees.

Sorption mechanisms of ionizable organic pollutants by biochars and approaches for the prediction of sorption are still unclear. In this study, batch experiments were conducted to explore the sorption mechanisms of woodchip-derived biochars prepared at 200-700 °C (referred as WC200-WC700) for cationic, zwitterionic and anionic species of ciprofloxacin (referred as CIP+, CIP± and CIP-, respectively). The results revealed that the sorption affinity of WC200 for different CIP species was in the order of CIP± > CIP+ > CIP-, while that of WC300-WC700 remained the order of CIP+ > CIP± > CIP-. WC200 exhibited a strong sorption ability, which could be attributed to hydrogen bonding and electrostatic attraction with CIP+, electrostatic attraction with CIP±, and charge-assisted hydrogen bonding with CIP-. Pore filling and π-π interactions contributed to the sorption of WC300-WC700 for CIP+, CIP± and CIP-. Rising temperature facilitated CIP sorption to WC400 as verified by site energy distribution analysis. Proposed models including the proportion of the three CIP species and sorbent aromaticity index (H/C) can quantitatively predict CIP sorption to biochars with varying carbonization degrees. These findings are vital to elucidating the sorption behaviors of ionizable antibiotics to biochars and exploring potential sorbents for environmental remediation.

Estudo da adsorção de cromo usando biochar proveniente de bagaço de malte: cinética e termodinâmica

ABSTRACT: Brewer’s spent grain (BSG) is a residue from brewery production, that can be reused as adsorbent of heavy metals like Chromium (Cr). In this study, BSG was used as a biochar for Cr adsorption in batch adsorption experiments. The biochar pyrolysis temperature (500, 600 and 700ºC), pyrolysis time (30, 105 and 180 minutes) and zinc chloride concentration (5, 12.5 and 20%) were evaluated and optimized from a fractional factorial design. An equilibrium adsorption capacity of 78.13 mg.g-1 and a yield of 26.42% were achieved using 700ºC, 30 min, 12.5%. This biochar was applied to the adsorption of Cr in aqueous solution, under different stirring speeds (100, 150 and 200 rpm). The higher agitation speed reduced the adsorption capacity of the coal from 90 to 72 mg.L-1. In addition, the Cr adsorption equilibrium was reached before 100 min. The pseudo-first order model best described the Cr adsorption kinetics. The Redlich-Peterson isothermal model best fitted the experimental data, with the parameter g (close to 1) suggesting Langmuir’s assumptions as the most appropriate to describe the adsorption of Cr on the optimized activated carbon.

Meta-Analysis for Quantifying Carbon Sequestration and Greenhouse Gas Emission in Paddy Soils One Year after Biochar Application

The incorporation of biochar into soils has been recognized as a promising method to combat climate change. However, the full carbon reduction potential of biochar in paddy soils is still unclear. To give an overview of the quantified carbon reduction, a meta-analysis model of different carbon emission factors was established, and the life cycle-based carbon reduction of biochar was estimated. After one year of incorporation, biochar significantly increased the total soil carbon (by 27.2%) and rice production (by 11.3%); stimulated methane (CH4) and carbon dioxide (CO2) emissions by 13.6% and 1.41%, respectively, but having insignificant differences with no biochar amendment; and reduced nitrous oxide (N2O) emissions by 25.1%. The soil total carbon increase was mainly related to the biochar rate, whereas CH4 emissions were related to the nitrogen fertilizer application rate. Biochar pyrolysis temperature, soil type, and climate were the main factors to influence the rice yield. The total carbon reduction potential of biochar incorporation in Chinese paddy soils in 2020 ranged from 0.0066 to 2.0 Pg C using a biochar incorporation rate from 2 to 40 t ha−1. This study suggests that biochar application has high potential to reduce carbon emissions, thereby contributing to the carbon neutrality goal, but needs field-scale long-term trials to validate the predictions.

Accelerating Fe2+/Fe3+ cycle via biochar to improve catalytic degradation efficiency of the Fe3+/persulfate oxidation

The sluggish Fe3+/Fe2+ cycle was the rate-limiting step in the Fenton-like reaction, and metal-free carbonaceous materials are considered as emerging alternatives to solve this problem. However, the effect of carbon material properties on the distribution of reactive species remains poorly understood. This study investigated the possibility and mechanism of using biochar to accelerate the Fe3+/Fe2+ cycle to overcome the low efficiency of Fe3+/persulfate (PS) catalytic oxidation of phenanthrene. More importantly, the contribution of reactive species in the reaction systems with the variation of biochar pyrolysis temperatures was quantitatively studied. The results showed that medium-temperature derived biochar (BC500) had the greatest ability to enhance the Fenton-like system compared to the low- and high-temperature (BC350/700), and the first-order rate constant achieved 5.2 and 35.7-fold increase against the biochar/PS and Fe3+/PS systems, respectively. Using electrochemical evidence, sulfoxide probe tests, and steady-state concentration calculations, radicals yields were found to rise and then reduce with decreasing pyrolysis temperature, while the nonradical contribution of Fe(IV) increased to 56.3%. Electron paramagnetic resonance, Boehm titration, and Raman spectroscopy unraveled that the enhanced effect of biochar resulted from itself persistent free radicals, phenolic-OH, and edge defects, which enabled electron transfer between Fe3+ and biochar. Fe2+ was thus continuously generated and effectively activated the PS. This work enables a better understanding of the Fe3+-mediated Fenton-like reaction in the presence of biochar and provides a sustainable green strategy for Fenton chemistry with potential applications.

Converting Hybrid Mechanisms to Electron Transfer Mechanism by Increasing Biochar Pyrolysis Temperature for the Degradation of Sulfamethoxazole in a Sludge Biochar/Periodate System

In this study, sludge biochar was prepared under four pyrolysis temperatures (SBC300, SBC500, SBC700, and SBC900) and then was employed to activate periodate (PI) for the degradation of sulfamethoxazole (SMX). Various characterization methods were employed to investigate the effect of pyrolysis temperature on the physicochemical properties of sludge biochar and the activation capacity of periodate. The SMX adsorption capacity of SBCs and the ability of activating PI to degrade SMX increased with the increasing pyrolysis temperature. The degradation of SMX by the SBCs/PI systems was highly dependent on the initial pH of the solution and the dosage of SBCs. Mechanistic studies indicated that the degradation of SMX by the SBCs/PI system was mainly based on an electron-mediated transfer mechanism. Additionally, the electron transfer capacity of the SBCs affected the defects and the degree of graphitization. The contribution of free radicals to SMX degradation decreases with increasing pyrolysis temperature. Toxicity experiments demonstrated that the toxic elimination of SMX by the SBCs/PI system was enhanced with increasing pyrolysis temperature.

Enhanced 2,4,6-trichlorophenol removal from soil by electrokinetic remediation coupled with biochar in a permeable reactive barrier

Coconut shell biochars prepared from the oxygen free pyrolysis under 300–700 °C were incorporated in the permeable reactive barrier (PRB) for electrokinetic remediation (EK) to remove 2,4,6-trichlorophenol (2,4,6-TCP) from soil. The result indicated the removal of 2,4,6-TCP from the soil under EK was increased by about 2 folds using biochar in PRB than those without biochar PRB. The orthogonal test suggested that the voltage input rather than the pyrolysis temperature of biochar was the major factor governing the removal of TCP during the EK-PRB process. The optimum TCP removal reached over 55% under 2 V cm −1 of voltage, 700 °C pyrolysis temperature and 40 mg L −1 of initial TCP concentration. The roles of biochar during EK remediation were identified as three aspects: accelerating the migration of TCP in soil by enlarging the electroosmotic flow (EOF), enhancing the direct removal of TCP by adsorption, and promoting the electrochemical degradation of TCP. The biochar from high pyrolysis temperature was preferred to be coupled with EK for the removal of organic contaminants owing to its great ability of enhancing EOF as well as pollutant adsorption. • The removal of 2,4,6-trichlorophenol by electrokinetic remediation with biochar was increased by about 2 folds. • Biochar enhanced trichlorophenol migration, adsorption, and degradation in soil. • The optimum removal was obtained at 2 V cm −1 using the biochar from 700 °C.

Walnut shell biochar based sorptive remediation of estrogens polluted simulated wastewater: Characterization, adsorption mechanism and degradation by persistent free radicals

The presence of steroid hormones in aquatic ecosystems is of prevailing concern attributable to their potential for endocrine disruption. Biochar (BC) is capable of liquid organic pollutants removal because of distinctive characteristics. The purpose of this study was to investigate the results of steroid hormone removal by walnut shell biochar produced at pyrolysis temperatures ranging from 400 to 700 °C. Surface assimilation mechanism and degradation behavior of the most important estrogens: estrone (E1), 17 β -estradiol (E2), together with estriol (E3) were unequivocally supported by biochar characterization. The results indicated that the chemosorptive removal of estrogens was directly associated with the pyrolysis temperature of biochar due to completely different surface structure and chemical composition. The following conditions were investigated for maximum surface assimilation of estrogens: biochar at pyrolysis temperature 700 °C, pH 4, biochar dosage of 0.1 mg mL −1 , and estrogen concentration of 2500 μ g L −1 at 25 °C. The experimental data fit well with the Pseudo-second-order and Freundlich isotherm models. Through electron paramagnetic resonance spectrometry (EPR) and gas chromatograph–mass spectrometer (GC–MS) analysis, it was discovered that persistent free radicals contributed to estrogen degradation, and the estrogen degradation pathway was tentatively projected to support the intermediate merchandise. Based on the findings of this study, biochar will doubtless be used for the fast and economical removal of toxicant organic pollutants in water and sewer water. • Biochar was prepared for removing estrogens from wastewater. • The proper reaction conditions were recommended for estrogens removal. • Persistent free radicals contributed to the degradation of estrogens.

Effect of pyrolysis temperature of biochar on Cd, Pb and As bioavailability and bacterial community composition in contaminated paddy soil

To further investigate the effect of pyrolysis temperature on bioavailable Cd, Pb and As, as well as the bacterial community structure in multi-metal(loid) contaminated paddy soil, six types of biochar derived from wood sawdust and peanut shell at 300 °C, 500 °C and 700 °C were prepared and incubated with Cd, Pb and As contaminated paddy soil for 45 days. The results showed that adding biochar decreased bioavailable Cd by 31.3%− 42.9%, Pb by 0.61–56.1%, while bioavailable As changed from 9.68 mg kg−1 to 9.55–10.84 mg kg−1. We found that pyrolysis temperature of biochar had no significant effect on Cd bioavailability while Pb bioavailability decreased obviously with pyrolysis temperature raising. Biochar reduced the proportion of soluble and exchangeable Cd from 45.0% to 11.2–15.4% in comparison with the control, while no significant effect on the speciation of Pb and As. Wood sawdust biochar (WSBs) had more potential in decreasing bioavailable Cd and Pb than peanut shell biochar (PSBs). Although high-temperature biochar resulted a larger increase in bacterial species than low-and mid- temperature biochar, feedstock played a more important role in altering soil bacterial diversity and community composition than pyrolysis temperature. PSBs increased the diversity of soil bacteria through elevating soil dissolved carbon (DOC). Biochar altered soil bacterial community structure mainly by altering the level of soil electricity conductivity, DOC and bioavailable Cd. In addition, applying high-temperature PSBs increased the genus of bacteria that relevant to nitrogen cycling, such as Nitrospira, Nitrosotaleaceae and Candidatus_Nitrosotalea.