Rice Straw-derived Biochar Research Articles

Amino/MnO2 combined modified biochar for enhancing Pb2+ and Cd2+ removal and mechanisms from aqueous solution

Heavy metals from aqueous solutions tend to pose toxicity to the environment, hence it is urgent to treat this pollution. Current studies have exhibited the adsorption capacity of original biochar for Pb2+ and Cd2+ in water, while effective methods were lacking to enhance its adsorption capacity and alleviate competitive adsorption. In this study, MnO2 and amino group combined modification was proposed to improve the Pb2+ and Cd2+ adsorption capacity of rice straw-derived biochar (MNBC) in water. The adsorption performances and mechanisms of MNBC were obtained from batch experiments, several characterizations, and DFT calculation. The results found that modified methods rose the variety of functional groups variety and improved the pore structure of biochar. Maximum removal rates for Pb2+ and Cd2+ were 96.18 % and 64.26 % and still reached 87.6 % and 54.4 % after four cycles in single Pb2+ or Cd2+ system. Cation exchange as well as electrostatic attraction might the main adsorption mechanism in the Pb2+ and Cd2+ adsorption process. In binary system, theoretical calculation exhibited that electron cloud neared Pb was more possible to transfer with adsorbent than that of Cd, which was accordance to the results of competitive adsorption. The p orbital of O atom in MnO2 and N orbital atom in amino groups could hybridize with d orbital of Cd and Pb, which effectively reduced the effect of competitive adsorption. Overall, this study proved removal prospect of MNBC for Pb2+ and Cd2+ and its highly efficient and stable in application.

Biochar Application Improved Sludge-Amended Landscape Soil Fertility Index but with No Added Benefit in Plant Growth

Co-application of sewage sludge (SS) with biochar in landscape/forestry soil is a common strategy for enhancing soil fertility and reducing the bioavailability of potential toxic elements (PTEs) derived from SS, such as Cd, Pb, Cu, Zn, and Ni. However, due to variability of biochar quality and uncertainties in responses of different plant species, whether the co-application benefits the landscape/forestry plant system remains elusive. Here, we tested the effectiveness of three types of biochar (SS-derived biochar (SB), rice straw-derived biochar (RB), and litter-derived biochar (LB)), which were added to soil amended with SS at 50% (w/w) at rates of 1.5%, 3%, and 4.5% as growth media for the landscape plant Aglaonema modestum (A. modestum). We analyzed the substrate’s physicochemical properties and assessed the alleviation of phytotoxicity by biochar application. A significant increase in the fertility index of substrate was observed in all the treatments with biochar addition. The addition of biochar reduced the potential mobility of PTEs while increasing their residual fraction in media. Nonetheless, it has been found that the addition of biochar has ineffective or even negative effects on A. modestum growth (height, biomass, root length) and nutrient absorption. Importantly, the reduction in root biomass and the increased activity of root antioxidant enzymes (SOD, POD, CAT, and MDA) indicate contamination stress of biochar on the roots of A. modestum. Toxic elements of concern—namely Cu, Cd, and Pb—were not significantly higher in tissues of A. modestum saplings planted in biochar-SS-amended soil. However, elevated levels of other elements that may pose toxicity concerns, such as Ni and Zn, increased in tissues at high biochar dosages. Based on the Entropy–Weight TOPSIS method, it was further confirmed that compared to the treatment without biochar, all treatments except for 3.0% LB application resulted in poorer A. modestum comprehensive growth. Our results emphasize the need for detailed research on the response of specific plants to biochar in specific environments, including plant adaptability and the unexplored toxicity of biochar, to understand the large variations and mechanisms behind these ineffective or negative effects before the large-scale co-utilization of SS and biochar in landscape/forestry soils.

Mitigating methane emissions and global warming potential while increasing rice yield using biochar derived from leftover rice straw in a tropical paddy soil

The sustainable management of leftover rice straw through biochar production to mitigate CH4 emissions and enhance rice yield remains uncertain and undefined. Therefore, we evaluated the effects of using biochar derived from rice straw left on fields after harvest on greenhouse gas emissions, global warming potential (GWP), and rice yield in the paddy field. The experiment included three treatments: chemical fertilizer (CF), rice straw (RS, 10 t ha−1) + CF, and rice straw-derived biochar (BC, 3 t ha−1 based on the amount of product remaining after pyrolysis) + CF. Compared with CF, BC + CF significantly reduced cumulative CH4 and CO2 emissions, net GWP, and greenhouse gas emission intensity by 42.9%, 37.4%, 39.5%, and 67.8%, respectively. In contrast, RS + CF significantly increased cumulative CH4 emissions and net GWP by 119.3% and 13.8%, respectively. The reduced CH4 emissions were mainly caused by the addition of BC + CF, which did not increase the levels of dissolved organic carbon and microbial biomass carbon, consequently resulting in reduced archaeal abundance, unlike those observed in RS + CF. The BC + CF also enhanced soil total organic carbon content and rice grain yield. This study indicated that using biochar derived from leftover rice straw mitigates greenhouse gas emissions and improves rice productivity in tropical paddy soil.

In situ growth of MIL-100(Fe) onto the rice straw-derived biochar for efficient adsorption of gaseous ammonia

Ammonia (NH3) is the primary odor-causing substance in compost waste gas, which can cause irreversible damage to the environment and humans, and is also a significant contributor to the formation of PM2.5. In this study, a novel composite adsorbent (MIL-100/RSB) for efficient adsorption of NH3 was fabricated by in situ growth of MIL-100(Fe) onto biochar derived from waste rice straw through hydrothermal synthesis. The resulting optimized MIL-100/RSB-0.5-700-0.4 (where 0.5 represented the mass ratio of K2CO3 activator to rice straw, 700 denoted pyrolysis temperature and 0.4 corresponded to the mass ratio of Fe-MOFs to biochar) was acquired by rationally adjusting the activation ratio, pyrolysis temperature and loading amounts of Fe-MOFs. The MIL-100/RSB-0.5-700-0.4 delivered a superior NH3 adsorption capability of 6.7 mmol/g at 298 K and 100 kPa with a rapid adsorption kinetics (achieving about 96 % of equilibrium sorption capacity after 30 min). In contrast, the inactivated biochar (carbonization without activator) only exhibited a much lower adsorption capacity at approximately 1.85 mmol of NH3/g. Additionally, the MIL-100/RSB showed favorable regeneration ability, retaining 3.62 mmol/g after undergoing six regeneration cycles. The adsorption mechanism of MIL-100/RSB was found to involve both physical and chemical adsorption process. Therefore, the as-prepared MIL-100/RSB composite offers a potentially promising carbon-based adsorbent for practical applications in the NH3 capture field.

Combined effects of microcystin-LR and rice straw-derived biochar on the hepatic antioxidant capacity of zebrafish: Insights from LC-MS/MS-based metabolomics analysis

Microcystin-LR (MC-LR) produced by cyanobacteria blooms poses a serious risk to aquatic organisms. Rice straw-derived biochar (BC) is gradually being utilized as an effective adsorbent to remove water pollutants. In the present study, the combined toxicity of MC-LR and BC on hepatic antioxidant capacity and metabolic phenotype of zebrafish (Danio rerio) were conducted due to the increasing concern of eutrophication in aquatic environments. Female zebrafish were exposed to solutions of MC-LR (10 μg/L) and BC (100 μg/L) individually and in combination for 30 days. The results indicated that sub-chronic MC-LR exposure induced oxidative stress and metabolic disorders, with a significant elevation of several amino acids, glucose as well as unsaturated fatty acids. Metabolic pathway analysis showed that the ascorbate and aldarate metabolism and biosynthesis of unsaturated fatty acids were affected under MC-LR stress. Significantly increased MDA levels along with significantly decreased CAT and GPx activities were observed in the MC-LR group. Nevertheless, MDA levels, antioxidant enzyme activities, and the relevant gene expressions (cat1, nrf2a, HO-1, keap1a) returned to baseline in the co-exposure group. These findings revealed that MC-LR resulted in metabolic disorders of protein, sugar, and lipid related to energy production, and BC could relieve MC-LR-induced metabolic disorder and oxidative stress in the liver of zebrafish. However, the potential risk of BC-induced metabolic disorder should not be neglected. Our present results highlight the potential of BC as a tool for mitigating the negative impacts of MC-LR on aquatic organisms in blooms-contaminated water.

Efficient removal of phytochrome using rice straw-derived biochar: Adsorption performance, mechanisms, and practical applications

Rice straw derived biochar was fabricated and applied as a purification agent. The adsorption kinetics, isotherms, and thermodynamics for adsorbates were determined using the biochar. Adsorption kinetics and isotherms were best fitted by the pseudo-second order and Langmuir models. Biochar could effectively remove chlorophyll in 9 different solutions. Biochar was employed as a clean-up reagent for 149 pesticides detection, which revealed that biochar had a higher phytochrome removal capacity than graphitized carbon black and 123 pesticides had satisfactory recovery values. The biochar was prepared into a sample pad by electrospinning and was then used for online sample clean-up in a test strip, and it showed high ability of removing phytochrome and improving detection sensitivity. Thus, biochar could be applied as a purification agent to remove pigmentation, making it a promising candidate not only for sample pretreatment but also in the fields of food, agriculture and environment.

PFAS removal from water by adsorption with alginate-encapsulated plant albumin and rice straw-derived biochar

Adsorption using conventional activated carbon is considered an effective and practical method for per- and polyfluoroalkyl substances (PFAS) removal from contaminated water. However, this application can be limited by long equilibrium times, poor performance in adsorbing short-chain PFAS, and compromised adsorption in the presence of other organic compounds. In this work, rice straw-derived biochar and albumin extracted from Moringa oleifera seeds were compared after encapsulation into alginate beads which were then investigated for removing two PFAS compounds, PFOS (long-chain) and PFBS (short-chain), from aqueous solutions. The effect of albumin and biochar concentrations and the influence of different pre-treatment conditions of biochar production on PFAS removal efficiency were investigated. The batch test results showed a high removal efficiency for PFOS with 1.5 g L−1 of either albumin-alginate beads (up to 87 %) or biochar-alginate composite beads (up to 99 %) for <16 h. While PFBS removal by albumin-alginate composite beads was low (10 %), the diammonium phosphate treated biochar–alginate beads achieved nearly 40 % in <48 h, outperforming some previously reported natural material-based adsorbents that were tested under similar experimental conditions. Adsorption with biochar-alginate beads appeared not to be pH dependent, and the presence of NOM (natural organic matter) did not greatly reduce the removal of either PFOS or PFBS. Hydrophobic sorption was shown to dominate over the electrostatic interaction in the PFAS adsorption. Overall, the potential of the rice straw-derived biochar-alginate beads for the remediation of PFAS in aqueous systems was demonstrated.

Adsorption of antibiotic, heavy metal and antibiotic plasmid by a wet-state silicon-rich biochar/ferrihydrite composite to inhibit antibiotic resistance gene proliferation/transformation

Decreasing bioaccessible antibiotics, heavy metals, and antibiotic resistance genes (ARGs) in soil by adsorption is an attractive, but unrealized, approach for ARG risk reduction. This approach has the potential to reduce the (co)selection pressure from antibiotics and heavy metals on bacteria and ARG horizontal gene transformation to pathogens. Here, a wet-state silicon-rich biochar/ferrihydrite composite (SiC–Fe(W)) synthesized by loading ferrihydrite onto rice straw-derived biochar was examined for i) adsorption of oxytetracycline and Cu2+ to reduce (co)selection pressure and ii) adsorption of extracellular antibiotic resistance plasmid pBR322 (containing tetA and blaTEM-1) to inhibit ARG transformation. SiC–Fe(W) gained the adsorption priority of biochar (for Cu2+) and wet-state ferrihydrite (for oxytetracycline and pBR322) and showed adsorptive enhancement (for Cu2+ and oxytetracycline) from a more wrinkled and exposed surface from biochar silica-dispersed ferrihydrite and a more negatively charged biochar, and the adsorption capacity for SiC–Fe(W) was 17–135 times that of soil. Correspondingly, 10 g/kg SiC–Fe(W) amendment increased the soil adsorption coefficient Kd by 31%–1417% and reduced the selection pressure from dissolved oxytetracycline, co-selection pressure from dissolved Cu2+, and transformation frequency of pBR322 (assessed with Escherichia coli). The development of Fe–O–Si bonds on silicon-rich biochar in alkaline enhanced ferrihydrite stability and adsorption capacity (for oxytetracycline), presenting a new potential strategy of biochar/ferrihydrite composite synthesis for adsorptive inhibition of ARG proliferation and transformation in ARG pollution control.

Biochar as an enhancer of the stability, mesoporous structure and oxytetracycline adsorption capacity of ferrihydrite: Role of the silicon component

The char component of biochar can act as an electron shuttle and redox agent to accelerate the transformation of ferrihydrite, but how the silicon component of biochar affects ferrihydrite transformation and pollutant removal remains unclear. In this paper, infrared spectroscopy, electron microscopy, transformation experiments and batch sorption experiments were conducted to examine a 2-line ferrihydrite formed by alkaline precipitation of Fe3+ on a rice straw-derived biochar. Fe-O-Si bonds were developed between the precipitated ferrihydrite particles and biochar silicon component, increasing mesopore volume (for mesopores with diameters of 10–100 nm) and surface area of ferrihydrite as the Fe-O-Si formation probably alleviated the aggregation of ferrihydrite particles. The Fe-O-Si bonding-contributed interactions blocked the transformation to goethite for ferrihydrite precipitated on biochar in a 30-day ageing and a 5-day Fe2+ catalysis ageing. Moreover, there was an increase of oxytetracycline adsorption capacity onto ferrihydrite-loaded biochar, which reached amazingly 3460 mg/g at the maximum, due to the Fe-O-Si bonding-contributed increase of surface area and oxytetracycline coordination sites. Ferrihydrite-loaded biochar as a soil amendment enhanced oxytetracycline adsorption and reduced the bacterial toxicity of dissolved oxytetracycline better than ferrihydrite did. These results provide new perspectives for the role of biochar (especially its silicon component) as an iron-based material carrier and a soil additive in the environmental effects of iron (hydr) oxides in water and soil.

Straw is more effective than biochar in mobilizing soil organic phosphorus mineralization in saline-alkali paddy soil

Fertilizer management can alter the availability and biological cycle of soil phosphorus (P). The objective of this study was to explore the relationship among soil P availability, organic phosphorus (Po) mineralization and soil bacteria characteristics under organic and inorganic fertilization in saline-alkali paddy soil. Four treatments were designed, namely no fertilizer (Control), mineral fertilizer (NPK), mineral fertilizer with rice straw (NPKS) or rice straw-derived biochar (NPKB). Compared with NPK treatment, straw and biochar addition greatly increased P uptake by rice while decreased soil organic P/total P ratio. The contents of soil available P (AP) and alkaline phosphatase (ALP) in NPKS treatment were higher than those in NPKB treatment. This was most likely due to the higher abundance of Streptomyces in NPKS treatment than that in NPKB treatment, which was known as a potential Po mineralizer. NPKS and NPKB treatments significantly increased diversity and abundance of phoD-harboring bacteria but have no significant effect on the total bacteria. Based on SEM analysis, the composition of phoD-harboring bacteria community was more important in ALP activity than the increased phoD-harboring bacterial abundance and diversity. Soil dissolved organic carbon (DOC) content and DOC: AP ratio were the key factors affecting the formation of total bacterial and phoD-harboring bacterial community, which were significantly increased in NPKS treatment. Compared with biochar application, straw was more efficient in increasing the abundance of some phoD-harboring bacteria, which preferred carbohydrate-rich environments, thereby improving the availability of P and its potential biological transformation in saline-alkali paddy soil.

Long-Term Successive Seasonal Application of Rice Straw-Derived Biochar Improves the Acidity and Fertility of Red Soil in Southern China

Soil acidity is a crop production problem of increasing concern in acid red soil. The potential of biochar as a soil amendment/for soil acid management in agricultural fields is a recently recognized yet underutilized technology. Related evidence is currently limited to short-term indoor experiments with one-time BC applications and no crop cultivation, yet the degree to which soil acidity may be impacted by the biochar aging process on long-time scale remains unclear. To evaluate the effects of successive seasonal applications of rice straw-derived biochar (BC) on acidity and fertility of soil, a five-year outdoor column trial was conducted using wheat-millet rotated acidic upland soils from the south of China. BC was applied to the top 0–15 cm of soil at the rates of 0 (BC0), 2.25 (BCL), and 22.5 (BCM) Mg ha−1 with an identical dose of NPK fertilizers at the beginning of each crop season. Our results showed that the wheat-millet biomass yield gradually decreased over five rotation cycles in BC0 without BC application. In contrast, after five rotations, BCM led to an increase in the total wheat/millet grain yield by 138%, and the straw yield increased by 253% compared to the control. The cumulative above-ground nutrient uptake of P, K, Ca, Na, and Mg in BCM also increased by 139%, 171%, 129%, 182%, and 71%, respectively, compared to that in the control. This positive effect was attributed to the increase in soil pH (3.29 units), cation exchange capacity (5.66 cmol kg−1), soil available P (241%), K (513%), Ca (245%), Mg (265%), exchange base (3.36 cmol kg−1), base saturation percentage (65.7%), and decrease in the exchangeable acidity, especially exchangeable Al3+ content (&lt;0.1 cmol kg−1). Our results demonstrated that rice straw-derived BC application to soil at 22.5 t ha−1 was found to be highly consistent in decreasing soil acidity and reducing soluble and exchangeable Al3+, indicating its higher ameliorating capacity in the south of China in the long run.

Development of Rice Straw-derived Biochar-Bentonite Composite and its Application for in situ Sequestration of Ammonium and Phosphate Ions in the Degraded Mine Soil.

Nutrient pollution has a diverse impact on the environment and human health. The presence of nutrients, such as ammonium and phosphate, is ubiquitous in the environment due to their extensive use in agricultural land and leaching through non-point sources. In this context, biochar-based composites could play an essential role in improving the soil's nutrient retention capacity. The present study aims to develop bentonite-biochar composites (BNT@BC 400 and 600) and utilize them as an ameliorating material in the coal mine degraded soil to reduce the leaching of ammonium and phosphate ions. The bentonite-biochar composite (BNT@BC 400 and 600) was synthesized using the pristine rice straw-derived biochar using the solvothermal method. The biochar was produced at two different pyrolytic temperatures, 400 °C and 600 °C, and denoted as BC 400 and 600, respectively. Hence, the bentonite-biochar composite was denoted as BNT@BC 400 and 600. The BNT@BC 400 and 600 were characterized using the elemental, proximate, SEM, XRD, and FTIR analysis. Subsequently, the BNT@BC composites were evaluated for the adsorptive removal of NH4+ and PO43- ions using batch adsorption and column leaching studies. In the soil columns, the BNT@BC 400 and 600 were mixed with the soil at two different application rates, viz. 1 and 2.5% (w/w). The leaching characteristics data were fitted using three different fixed-bed models to predict the maximum adsorption capacity of the amended soil columns and the dominant mechanism of adsorption. Results indicated that the BNT@BC 600 showed the maximum adsorption capacity of 33.77 and 64.23 mg g-1 for the adsorption of NH4+ and PO43- ions, respectively. The dominant adsorption mechanisms in the aqueous solution were the electrostatic attraction, complexation, ion exchange, and precipitation processes. In the soil columns, the sorption of NH4+ and PO43- ions was governed by diffusive mass transfer and electrostatic interaction. Findings of the study indicated that incorporating the BNT@BC composite in the soil can significantly reduce the leaching of the NH4+ and PO43- ions and increase the overall soil fertility.

Biochar alleviating heavy metals phytotoxicity in sludge-amended soil varies with plant adaptability

Recycling sewage sludge (SS) to soil potentially causes soil heavy metal (HM) pollution and plant phytotoxicity. Biochar plays an important role in alleviating HM phytotoxicity, and responses vary with the feedstocks and usage of biochar. However, the effect of plant adaptability on biochar-mediated alleviation is poorly understood. Here, SS-derived biochar (SB) and rice straw-derived biochar (RB) applied at rates of 1.5% and 3% (W/W, SB1.5, SB3, RB1.5, and RB3) were used to improve the properties of soil amended with SS at 50% (W/W). Alleviation of phytotoxicity by biochar was further analyzed with SS-sensitive plant Monstera deliciosa and SS-resistant plant Ruellia simplex. Results revealed that both SB and RB significantly decreased the soil's bulk density and increased water retention. They also changed soil organic matter content and HMs fractionation. The addition of SB or RB alleviated the SS phytotoxicity, and they significantly promoted the growth and the root morphology and physiological index of M. deliciosa. But for R. simplex, these significant changes only synchronously occurred in SB3 treatment. The alleviation in M. deliciosa was more prominent and more closely connected with soil property changes than in R. simplex. Also, more soil property predictors were observed to play an important role in M. deliciosa growth than in R. simplex growth. These results indicated that biochar alleviating HMs phytotoxicity in SS-amended soil is associated with the changes of soil property. Moreover, the alleviation varies more prominently with plant adaptability than with biochar feedstocks and usage.

Insights into the anaerobic digestion of fecal sludge and food waste in Tanzania

With the increasing demand for renewable energy and environmental protection, biogas technology has attracted considerable attention around the world. Fecal sludge (FS) is rich in organic matter, and it contains high concentrations of excreted pathogens that cause gastro-intestinal infection. In Tanzania, fecal sludge management from on-site sanitation systems poses a threat on environmental safety. This study aimed to assess the feasibility of the use of anaerobic digestion (AD) for the treatment of FS and the production of biogas as renewable energy to achieve multiple benefits in Tanzania. For the experiments, FS and food waste (FW) were used as feedstock, and rice straw-derived biochar (RSB) was added as an additive to improve biogas production. The mesophilic anaerobic digestion resulted in a methane yield of 287.5 ml/g VS for FS + FW co-digestion and 396 ml/g VS for FS + FW + RSB co-digestion. At ambient temperature (20–26°C), the system produced a methane yield of 234 ml/g VS for FS + FW co-digestion and 275 ml/g VS for FS + FW + RSB co-digestion. Three different scenarios (digester with volumes of 4, 100, and 400 m3, respectively) and strategies for FS treatment by AD in Tanzania were proposed and analyzed. These treatments can produce methane volumes of 1.95, 49.5, and 199.5 m3 with pay-back periods of 3, 5, and 15 years and net present values of + 28, +1,337, and +52,351 USD, respectively. The calculations also showed that the heat value from the produced biogas and energy needed to heat the digester at 26–37°C resulted in energy balance values of + 0.012, + 0.53, and + 2.22 GJ/day for the 4, 100, and 400 m3 digester volumes, respectively.

Energy recovery and waste treatment using the co-pyrolysis of biomass waste and polymer.

The pyrolysis of spent coffee grounds (SCG) and polymers was examined as a waste treatment option for energy recovery and carbon sequestration. Rice straw-derived biochar was used as control biochar to evaluate the sorption capacity and energy production capability of SCG-derived biochar. SCG are characterised by high levels of volatile matter, rendering them suitable as an energy source. SCG were converted to biochar, bio-oil, and syngas via pyrolysis, with yields of 22%, 33%, and 45%, respectively. The high heating value (HHV) of the biochar and bio-oil was 20.6 and 22.9 MJ kg-1, respectively, indicating that they could be used as supplementary fuels. Co-pyrolysis with polymers (20 v v%-1) increased the HHV of biochar. Accordingly, the maximum production of CH4 and H2 increased from 0.3 and 0.04 mmol g-1 to 3.4-6.3 and 0.8-1.3 mmol g-1, respectively. Polystyrene most strongly enhanced the yields of CH4 and H2, followed by polypropylene and polyethylene; this order was likely to be in accordance with the number of carbon and hydrogen atoms present in the monomers. Similar to rice straw-derived biochar, the biochar produced from SCG demonstrated a high sorption capacity for 2,4-dinitrotoluene and chromate due to its high carbon content and anion exchange capacity, respectively. Laboratory pot tests revealed that the coffee grounds-derived biochar was able to increase the growth of young radish. Our results suggest that the pyrolysis of SCG and polymer may be a promising option for waste treatment, energy production, and carbon sequestration.

Effects of straw and straw-derived biochar on bacterial diversity in soda saline-alkaline paddy soil

PurposeIn order to provide a scientific basis for the improvement of soda saline-alkaline paddy soil, the pot experiment was performed to explore the effects of rice straw and straw-derived biochar on the diversity of soil bacteria and community structure in soda saline-alkaline soil.MethodsThe experiment was four gradients of straw return (3 (RS1), 7.5 (RS2), 12 (RS3), and 16.5 (RS4) t/hm2) and four gradients of biochar return (3 (RB1), 7.5 (RB2), 12 (RB3), and 16.5 (RB4) t/hm2), using 0 t/hm2 as a control (CK). After 5 consecutive years of measuring straw returns, high-throughput sequencing was used to determine the relative abundance, alpha diversity, and changes in the community structure of soil bacteria.ResultOur results demonstrated that straw return significantly increased the relative abundance of Bacteroidetes, Firmicutes, and Sphingomonas and significantly reduced the relative abundance of Acidobacteria, Actinobacteria, Gemmatimonadetes, Parcubacteria, Anaeromyxobacter, Pontibacter, uncultured_bacterium_f_Draconibacteriaceae, and Bryobacter. Straw-derived biochar return significantly increased the relative abundance of uncultured_bacterium_f_Draconibacteriaceae and significantly reduced the relative abundances of Actinobacteria, Gemmatimonadetes, Thiobacillus, and Anaeromyxobacter, indicating that both straw and its associated biochar return changed the relative abundance of the phyla and genera of some bacteria. Straw return affected bacteria phylum and genus more than straw-derived biochar. With the exception of the 16.5 t/hm2 straw return, which reduced bacterial richness, the treatments did not significantly impact alpha diversity. Compared with straw-derived biochar return, straw return significantly changed the bacterial community structure, and the higher the straw return, the higher the impact on the bacterial community structure. Redundancy analysis (RDA) demonstrated that there was a significant correlation between the physicochemical properties of the soil and the community structure of its bacteria. A Mantel test demonstrated that the content of available phosphorus, available potassium, and organic matter was all important environmental factors affecting community structure.ConclusionWe speculate that straw return regulates the physicochemical properties of the soil, which affects the bacterial community structure.

Ozonation of phenol in the presence of biochar and carbonaceous materials: The effect of surface functional groups and graphitic structure on the formation of reactive oxygen species

To develop a novel oxidation process using ozone and carbonaceous materials for water treatment and groundwater remediation, the effect of carbonaceous materials on the ozonation of phenol was investigated via batch experiments. Anode carbonaceous material (ACM) recovered from spent Li-ion batteries, graphite, granular activated carbon (GAC), and rice straw-derived biochar were evaluated as catalysts to enhance the ozonation of phenol. Compared with direct ozonation (28% removal in 2 h), the addition of carbonaceous materials enhanced the oxidation of phenol by ozone, showing 47%, 45%, 81%, and 74% removal with ACM, graphite, GAC, and biochar, respectively. According to the quenching experiments with chemical reagents and electron paramagnetic resonance analysis, reactive oxygen species, such as hydroxyl radicals (·OH), superoxide radicals (O2·-), and singlet oxygen (1O2), as well as electron transfer in the mediated-reaction, are included in the ozonation of phenol in the presence of carbonaceous materials. The oxygen-containing surface functional groups and graphitic structure are responsible for the reactive oxygen species and electron transfer reactions, respectively. Our results suggest that carbonaceous materials may be effectively used as catalysts to promote the ozonation of recalcitrant contaminants in water.

Alleviation of microcystin-LR-induced hepatic lipidosis and apoptosis in zebrafish by use of rice straw-derived biochar

Microcystin-LR (MC-LR), mainly released by Microcystis aeruginosa, is posing a tremendous risk to aquatic animals and human health. Meanwhile, biochar (BC) is gradually be used as a sustainable adsorbent to immobilize and remove water pollutants. In our study, we for the first time conducted a full-scale investigation on lipid metabolism and its regulation mechanism of female zebrafish (Danio rerio) exposed to 0, 10 μg/L MC-LR, 100 μg/L BC, and 10 μg/L MC-LR+ 100 μg/L BC. The results indicated that sub-chronic MC-LR exposure induced hepatic lipidosis and apoptosis, including the formation of lipid droplets, significantly elevation of hepatic triglyceride (TG) level as well as significant upregulated expression of lipogenesis-related genes (foxo1a, elovl5, pparγ) and pro-apoptotic genes (bax, casp3). Nevertheless, no significant alteration was observed in the single BC group and the combined exposure group, which indicated that BC may solely functioned as an absorbent agent to lower MC-LR bioaccumulation in zebrafish liver and alleviate MC-LR-induced hepatotoxicity. Our findings revealed that the utilization of rice straw-derived BC can adsorb and immobile MC-LR in the water, subsequently alleviated the MC-LR-induced hepatic lipidosis and apoptosis in female zebrafish. On the basis of fish health, it is urgent to explore the feasibility of using environmentally friendly materials like BC to adsorb pollutants in water.

Efficient removal of tetracycline from water by tannic acid-modified rice straw-derived biochar:Kinetics and mechanisms

Rice straw-derived biochar (BC) has the advantage of low cost to remove tetracycline (TC) as a potential adsorbent, but it is limited by its poor adsorption capacity. On this basis, it was modified with tannic acid (TA) by precovering to increase the number of oxygen-containing functional groups. The structure and chemical properties of the modified BC were characterized and the adsorption behavior of TC on the modified BC was tested. The adsorption kinetics and isothermal data indicated that the adsorption performance of TC was improved after modification, and the adsorption capacity reached 308 mg/g, which was better than other congeneric adsorbents. The adsorption mechanism mainly included physical adsorption, electrostatic interaction, hydrogen bonding, and π–π interaction. The results of this study revealed that TA promoted the removal of TC from BC, and it was also beneficial to the rice straw-derived BC as an engineering adsorbent for the removal of TC from water.

Performance evaluation of crop residue and kitchen waste-derived biochar for eco-efficient removal of arsenic from soils of the Indo-Gangetic plain: A step towards sustainable pollution management

Biochar was produced from wheat straw (Triticum aestivum), rice straw (Oryza sativa), and kitchen waste at varying pyrolysis temperatures (300°C–700 °C). The biochars were screened depending on their production and physicochemical properties for the adsorptive removal of arsenic (As). The morphological analysis by Field emission scanning electron microscope revealed a porous biochar surface. Spectroscopic characterization of biochars indicated the co-existence of minerals, carboxyl, carbonyl, amide, and hydroxyl groups, which implies the suitability of biochar to immobilize metal (loid)s from soils. Changes in peaks were observed in Fourier-transform infrared and X-ray diffraction images after As sorption indicating the involvement of chemisorption. The thermogravimetric analysis and a low H/C value derived from the CHNS analyzer confirmed the high stability of biochar. The BET analysis was used to estimate the surface areas of wheat straw (15.8 m2 g-1), rice straw (12.5 m2 g-1), and kitchen waste (2.57 m2 g-1) -derived biochars. Batch sorption studies were performed to optimize experimental parameters for maximum removal of As. Maximum removal of As was observed for wheat straw-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 initial concentration (IC), 7.5 % dose, 25 °C temperature, and 60 min contact time (83.7 ± 0.06 %); in rice straw-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 IC, 7.5 % dose, 25 °C temperature, 90 min contact time (83.6 ± 0.37 %); and in kitchen waste-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 IC, 5 % dose, 25 °C temperature, 60 min contact time (76.7 ± 0.16 %). The sorption model parameters suggested the possibility of chemisorption, physisorption, diffusion, and ion exchange for the removal of As. Therefore, it could be recommended to farmers that instead of disposing or burning straws and waste openly, they could adopt the process of charring to generate livelihood security and mitigation of geogenic contaminants from the soil/water dynamic systems.