Impact of varying dissolved organic carbon load on sediment phosphorus release and its periodic mechanisms.

Phosphorus (P) release from sediment poses a severe challenge for eutrophication management in the aquatic environment. The dissolved organic carbon (DOC) concentrations in riverine ecosystems have shown an increasing trend due to intensified climate change and anthropogenic activities, while their impact on sediment P cycling remains unclear. To investigate the effects of different DOC loads on sediment P release and the underlying mechanisms, we conducted a two-month experiment in 15 plexiglass tanks, with five gradient-increasing target DOC concentrations set according to reality: control (S0), 5 mg/L (S5), 10 mg/L (S10), 15 mg/L (S15), and 20 mg/L (S20). The results demonstrated that: i) DOC enrichment promoted the sediment P mobilization and release, with the underlying mechanisms exhibited periodic characteristics. ii) reduced dissolved oxygen (DO) concentration and stimulated alkaline phosphatase activity (APA) were likely the primary and sustained facilitating mechanisms. While after the termination of DOC load, elevated pH level was also considered a contributing factor when chlorophyll a (Chl a) ranged between 5.9 µg/L and 7.7 µg/L iii) ultimate concentration of total P (TP) in the overlying water depended on DOC load. After DOC addition was terminated, decreased TP concentrations were observed when DOC concentration was in the range of 5-15 mg/L, which may be attributed to the direct uptake of P by phytoplankton counteracting the minor promotion of P release induced by anoxic conditions. However, when DOC concentrations exceeded 15-20 mg/L, there were notable increments in TP concentrations. Our findings provide further insight into the response mechanisms of sediment P release to the increasing organic C load in natural ecosystems. The impact of broader C forms or C loads on sediment P cycling needs to be fully elucidated and even quantified in future studies, especially through large-scale field investigations to further clarify the coupled roles between C and P.

Novel chitosan-ethylene glycol hydrogel for the removal of aqueous perfluorooctanoic acid.

It is urgent to explore an effective removal method for perfluorooctanoic acid (PFOA) due to its recalcitrant nature. In this study, a novel chitosan-based hydrogel (CEGH) was prepared with a simple method using chitosan and ethylene glycol through a repeated freezing-thawing procedure. The adsorption of PFOA anions to CEGH agreed well to the Freundlich-Langmuir model with a maximum adsorption capacity as high as 1275.9 mg/g, which is higher than reported values of most adsorbents for PFOA. The adsorption was influenced by experimental conditions. Experimental results showed that the main removal mechanism was the ionic hydrogen bond interaction between carbonyl groups (COO-) of PFOA and protonated amine (NH+) of the CEGH adsorbent. Therefore, CEGH is a very attractive adsorbent that can be used to remove PFOA from water in the future.

Adsorption of nitrate onto biochar derived from agricultural residuals.

To develop low-cost adsorbents for aqueous nitrate, biochars were prepared from three types of agricultural residuals at different pyrolysis temperatures (300 °C, 450 °C, and 600 °C). The corncob biochar produced at 600 °C (CC600) was the best nitrate adsorbent of all the tested biochars. Characterization results showed that CC600 had good thermal stability, porous structure, and abundant surface functional groups. Findings from batch adsorption experiments demonstrated that CC600 showed relatively fast adsorption kinetics to nitrate in aqueous solutions. In addition, the Langmuir adsorption capacity of CC600 to nitrate was 14.46 mg/g, comparable to that of other biochar-based adsorbents. Therefore, CC600 showed promising potential to be used as a low-cost adsorbent for the treatment of nitrate in water.

Constructed wetland using corncob charcoal substrate: pollutants removal and intensification.

To investigate the feasibility of using corncob charcoal substrate in constructed wetlands, four laboratory-scale vertical flow constructed wetlands (VFCWs) were built. Effluent pollutant (chemical oxygen demand (COD), NH4+-N, total phosphorus (TP)) concentrations during the experiment were determined to reveal pollutant removal mechanisms and efficiencies at different stages. In the stable stage, a VFCW using clay ceramisite substrate under aeration attained higher COD (95.1%), and NH4+-N (95.1%) removal efficiencies than a VFCW using corncob charcoal substrate (91.5% COD, 91.3% NH4+-N) under aeration, but lower TP removal efficiency (clay ceramisite 32.0% and corncob charcoal 40.0%). The VFCW with raw corncob substrate showed stronger COD emissions (maximum concentration 3,108 mg/L) than the corncob charcoal substrate (COD was lower than influent). The VFCW using corncob charcoal substrate performed much better than the VFCW using clay ceramisite substrate under aeration when the C/N ratio was low (C/N = 1.5, TN removal efficiency 36.89%, 4.1% respectively). These results suggest that corncob charcoal is a potential substrate in VFCWs under aeration with a unique self -supplying carbon source property in the denitrification process.

Performance of trichlorfon degradation by a novel Bacillus tequilensis strain PA F-3 and its proposed biodegradation pathway.

The novel trichlorfon (TCF)-degrading bacterium PA F-3, identified as Bacillus tequilensis, was isolated from pesticide-polluted soils by using an effective screening and domesticating procedure. The TCF biodegradation pathways of PA F-3 were also systematically elucidated. As revealed by high-performance liquid chromatography, the TCF residues in the mineral salt medium demonstrated that PA F-3 can utilize TCF as its sole carbon source and reach the highest degradation of 71.1 % at an initial TCF concentration of 200 mg/L within 5 days. The TCF degradation conditions were optimized using response surface methodology as follows: temperature, 28 °C; inoculum amount, 4 %; and initial TCF concentration, 125 mg/L. Biodegradation treatments supplemented with exogenous carbon sources and yeast extract markedly increased the microbial dry weights and TCF-degrading performance of PA F-3, respectively. Meanwhile, five metabolic products of TCF were identified through gas chromatography/mass spectrometry, and a biodegradation pathway was proposed. Results indicated that deoxidation and dehydration (including the cleavage of the P-C phosphonate bond and the C-O bond) were the preferred metabolic reactions of TCF in this TCF-degrading bacterium.

Enhancing lead adsorption capacity prediction in biochar: a comparative study of machine learning models and parameter optimization.

Machine learning models for predicting lead adsorption in biochar, based on preparation features, are currently lacking in the environmental field. Existing conventional models suffer from accuracy limitations. This study addresses these challenges by developing back-propagation neural network (BPNN) and random forest (RF) models using selected features: preparation temperature (T), specific surface area (BET), relative carbon content (C), molar ratios of hydrogen to carbon (H/C), oxygen to carbon (O/C), nitrogen to carbon (N/C), and cation exchange capacity (CEC). The RF model outperforms BPNN, improving R2 by 10%. Additional features and particle swarm optimization enhance the RF model's accuracy, resulting in an 8.3% improvement in R2, a decrease in RMSE by up to 56.1%, and a 55.7% reduction in MAE. The importance ranking of features places CEC > C > BET > O/C > H/C > N/C > T, highlighting the significance of CEC in lead adsorption. Strengthening the complexation effect may improve lead removal in biochar. This study contributes valuable insights for predicting and optimizing lead adsorption in biochar, addressing the accuracy gap in existing models. It lays the foundation for future investigations and the development of effective biochar-based solutions for sustainable lead removal in water remediation.

Nickel-loaded shrimp shell biochar enhances batch anaerobic digestion of food waste.

This study evaluated the effectiveness of shrimp shell biochar (SBC) and nickel (Ni) loaded SBC in increasing methane yield during anaerobic digestion of food waste. The results indicated that the methane yields of control (without SBC), SBC, SBC loaded with the low concentration of Ni, and SBC loaded with the high concentration of Ni were 81.8, 116.1, 134.7, and 99.2 mL/(g·VS), respectively. SBC promoted the efficiency and stability of the whole anaerobic digestion process including hydrolysis, volatile fatty acid conversion and methanogenesis. While the invigorating effect of loaded Ni at the low concentration of 0.88 mg/g was mainly concentrated in methanogenesis, the inhibition effect of the high Ni concentration was comprehensive. SBC helped Methanosarcina proliferation, and low concentration Ni promoted the number and activity of Methanosarcina and Methanosaeta. The results show that biochar loaded with a low level of trace elements such as Ni can promote the anaerobic digestion process.

Biomineralization of lead in wastewater: Bacterial reutilization and metal recovery.

Biomineralization has not been widely applied due to the lack of bacterial reusability, which needs to be investigated urgently. In this study, we found Lysinibacillus could immobilize Pb2+ at initial pH ≥ 2.0. Lead ion recovery and cell reutilization could be achieved efficiently at pH = 1.0 (c(HNO3) = 0.1 mol/L). Besides, the strong chelating agent EDTA-2Na (c(EDTA-2Na)= 0.1 mol/L) was used for comparison. The oxidative damaging effect of cells could be reduced by both eluents. Mechanism analysis was conducted through zeta potential measurement, 3D-EEM, cyclic voltammetry, FE-EPMA, XRD, FTIR, and XPS. After the cells were eluted by HNO3, the enzyme activity enhanced and the removal efficiency increased continuously. Cells were used to remove Pb2+ repeatedly, and regular-shaped Pb3(PO4)2 crystals were always formed. After the cells were eluted by EDTA-2Na, cells were more prone to redox reaction and were induced to produce mercaptan (R-SH). The active hydrogen in R-SH could react with peroxide free radicals. New free radicals were formed after the R-SH was stripped of hydrogen, and finally, PbS stable mineral was formed. This research provides a new strategy to realize bacterial reutilization, which is a breakthrough in the field of biomineralization.

Metabolic and Physiological Changes in the Roots of Two Oat Cultivars in Response to Complex Saline-Alkali Stress.

Saline-alkali stress is a major abiotic stress factor in agricultural productivity. Oat (Avena sativa L.) is a saline-alkali tolerant crop species. However, molecular mechanisms of saline-alkali tolerance in oats remain unclear. To understand the physiological and molecular mechanisms underlying seedling saline-alkali tolerance in oats, the phenotypic and metabolic responses of two oat cultivars, Baiyan7 (BY, tolerant cultivar) and Yizhangyan4 (YZY, sensitive cultivar), were characterized under saline-alkali stress conditions. Compared with YZY, BY showed better adaptability to saline-alkali stress. A total of 151 and 96 differential metabolites induced by saline-alkali stress were identified in roots of BY and YZY, respectively. More detailed analyses indicated that enhancements of energy metabolism and accumulations of organic acids were the active strategies of oat roots, in response to complex saline-alkali stress. The BY utilized sugars via sugar consumption more effectively, while amino acids strengthened metabolism and upregulated lignin and might be the positive responses of BY roots to saline-alkali stress, which led to a higher osmotic adjustment of solute concentrations and cell growth. The YZY mainly used soluble sugars and flavonoids combined with sugars to form glycosides, as osmotic regulatory substances or antioxidant substances, to cope with saline-alkali stress. The analyses of different metabolites of roots of tolerant and sensitive cultivars provided an important theoretical basis for understanding the mechanisms of saline-alkali tolerance and increased our knowledge of plant metabolism regulation under stress. Meanwhile, some related metabolites, such as proline, betaine, and p-coumaryl alcohol, can also be used as candidates for screening saline-alkali tolerant oat cultivars.

Mitigation of organic fouling of ultrafiltration membrane by high-temperature crayfish shell biochar: Performance and mechanisms.

The paper applied crayfish shell (CFS) biochar to the mitigation of ultrafiltration (UF) membrane fouling induced by humic acid (HA) and sodium alginate (SA). Results indicated that the high adsorption capacity of CFS800 to HA made it effective in alleviating the irreversible membrane fouling induced by HA, and the cross-linking reaction between the hydroxyl calcium components on CFS800 and SA reduced the reversible membrane fouling induced by SA rapidly. Further analysis showed that the "hydrogel flocs" generated by the cross-linking reaction would accumulate on the surface of the substrate membrane and form an amorphous hydrogel layer to intercept the subsequent foulant and purify the water quality further. Meanwhile, the mitigation performance of CFS800 was twice more than that of commercial powder activated carbon (PAC), and the dosage was the main factor affecting its practical application performance and thus could be considered as a promising material in alleviating membrane fouling induced by HA and SA. More importantly, the findings of the present study gave a new sight towards the application of biochar.

Continuous and efficient immobilization of heavy metals by phosphate-mineralized bacterial consortium.

Traditional sewage treatment technology cannot remove heavy metals, which needs to be improved urgently. Lysinibacillus with the function of bio-mineralization was screened and loaded on granular sludge to form a phosphate-mineralized bacterial consortium, which demonstrated the ability of self-regulating pH and automatic solid-liquid separation. Heavy metals could be fixed on the bacterial consortium to produce stable and harmless phosphate minerals. The highest removal efficiency of Pb(Ⅱ), Cd(Ⅱ), and Ni(Ⅱ) were 97.9%, 70%, and 40%, respectively. Organic matter and other metal ions in actual polluted water had little effect on the Pb(Ⅱ) removal efficiency. Mechanism analysis was conducted through 3D-EEM, XRD, SEM-EDS, XPS, FTIR, and high-throughput sequencing analyses. The bacterial consortium was a multi-species coexistence system, but Lysinibacillus played a major role in removing Pb(Ⅱ). C-O and O-H bonds of tyrosine and phosphorous organics were broken by enzyme catalysis and the metal-oxygen bond (Pb-O) was formed. Mineral crystals in the reactor accumulated, transforming from the initial phase non-crystalline structure to the metaphase Pb3(PO4)2 and eventually to the Pb5(PO4)3OH. This research obtained a promising technique for immobilizing Pb(Ⅱ) or other hazardous metals continuously and efficiently.

Kinetics, isotherm and chemical speciation analysis of Hg(â ¡) adsorption over oxygen-containing MXene adsorbent.

A facile method was used to prepare two-dimensional MXene for the treatment of heavy metal ions in wastewater. The adsorbent has good selectivity for the adsorption of Hg (Ⅱ) in mixed divalent cationic metal solutions due to a large number of oxygen-containing functional groups on the surface of the material. The adsorption of mercury was tested using mercuric chloride and mercury nitrate solutions. The Langmuir maximum adsorption capacity of the adsorbent at a pH of 5.0 and a temperature of 30 °C is 1057.3 mg/g (mercuric nitrate) and 773.29 mg/g (mercuric chloride), respectively. The adsorbent also maintains a high adsorption capacity at low pH (pH = 2.0). The removal rate of mercury-containing wastewater within 100 mg/L is nearly 100%. The chemical species of Hg-containing ions at different pH and temperatures was studied. It was found that the adsorbent could maintain a high adsorption capacity for different forms of Hg-containing ions.

Cadmium removal by MgCl2 modified biochar derived from crayfish shell waste: Batch adsorption, response surface analysis and fixed bed filtration.

Cadmium (Cd) pollution is regarded as a disturbing environmental problem due to its serious risks to the water body and human health. The removal of cadmium from wastewater is thus crucial to avoid its harmful effects on the ecosystem. This study comprehensively investigated Cd(II) adsorption onto MgCl2 modified biochar (MgC600) and results showed that the adsorption capacity of MgC600 was more than twice of that of pristine biochar due to its enhanced ion exchange ability. Response surface analysis revealed that reaction time played a crucial role in the Cd(II) adsorption, followed by initial concentration and solution pH. Moreover, the optimal adsorption conditions and capacity were precisely given by the quadratic regression model and thus proved that the model can be applied to predict the operation conditions of Cd(II) adsorption. Finally, a new model defined as BJP model [Formula: see text] was proposed and proved to be more suitable for the fixed bed filtration process. Overall, our findings provide a promising material in treatment of Cd(II)-rich wastewater and give a clear picture of its application. More importantly, the newly developed BJP model can accurately describe the fixed bed filtration process and further promote its application in wastewater treatment.

Removal of lead from acidic wastewater by bio-mineralized bacteria with pH self-regulation.

Microorganisms with the function of bio-mineralization were isolated from a soil. They were identified as urease-producing bacteria and phosphate-solubilizing bacteria. These two kinds of bacteria belong to the eosinophilic bacteria, which regulated the pH of solution and removed Pb2+ the best at the initial solution pH of 4. The Pb2+ removal mechanism was further explored using various techniques including zeta potential measurement, three-dimensional fluorescence, FTIR, XRD, and TEM-EDS. The results showed that extracellular adsorption, intracellular accumulation and bio-mineralization occurred at the same time and converted to each other. The extracellular adsorption of urease-producing bacteria was through electrostatic adsorption and gradually decomposed urea to produce PbCO3 minerals. The extracellular adsorption of phosphate-solubilizing bacteria was controlled by extracellular polymeric substances (EPS) and rapidly formation of Pb3(PO4)2 stable minerals. In addition, the stabilities of Lead minerals of the two strains were compared. The results showed that the precipitates of phosphate-solubilizing bacteria were more stable. While phosphate-solubilizing bacteria have some advantages, both strains can play important roles in bio-mineralization of HMs in acidic wastewater.

Crayfish shell biochar modified with magnesium chloride and its effect on lead removal in aqueous solution.

In this study, crayfish shell was pyrolyzed at 600 °C to obtain an unmodified biochar (CS600). MgCl2 was used as a modifier to pretreat crayfish shell to produce a modified biochar (CS600-MgCl2) under the same pyrolysis conditions. The two biochars were characterized for physicochemical properties and evaluated for lead (Pb2+) sorption ability to determine the modification mechanism. Mono-element batch adsorption experiments were conducted to compare the sorption performances of CS600 and CS600-MgCl2 to Pb2+ in aqueous solutions. All the experiments were carried out at pH of 7. According to the Freundlich-Langmuir model, CS600-MgCl2 had a higher adsorption capacity (152.3 mg/g) than CS600 (134.3 mg/g). FTIR, SEM, XRD, BET, and ICP analyses were applied to inform the interpretation of the mechanism. CS600 was calcium-rich and mainly removed Pb2+ through the ion exchange mechanism by replacing Ca2+ in the biochar. The increased Pb2+ adsorption capacity of CS600-MgCl2 was mainly due to the enlarged specific surface area and the formation of Mg3(OH)5Cl·4H2O on the modified biochar. Findings of this study suggest that both CS600 and CS600-MgCl2 can be used to remove heavy metal ions from wastewater and MgCl2 can improve the sorption performance of biochar.

Enhanced alginate-based microsphere with the pore-forming agent for efficient removal of Cu(â ¡).

In order to increase the adsorption properties of sodium alginate gel beads, a series of SA@PF-beads (sodium alginate-based beads with different amount of pore-forming agent) were prepared with calcium carbonate as the pore forming agent. The experimental results showed that the adsorption capacity of Cu(Ⅱ) increased by at least two times (from 13.69 mg/g to 33.88 mg/g, treated with SA@PF-0 and SA@PF-2.0, respectively) with proper amount of calcium carbonate added, which is economical and effective. In the experiment, SEM was used to measure the morphology of gel beads with different amount of pore-forming agent. FTIR and XPS were used to analyze the variation of functional groups and bond energies in the adsorption process. Adsorption isotherms and kinetics were conducted and showed that the adsorption process was consistent with Langmuir model and Elovich kinetic model. The maximum Langmuir adsorption 229.746 mg/g. The effects of pH, temperature and solid-liquid ratio on adsorption capacity were also investigated. In brief, calcium carbonate is an efficient and convenient pore-forming agent, which can be used to improve the adsorption properties of alginate gel materials.

Biodegradable chitosan-ethylene glycol hydrogel effectively adsorbs nitrate in water.

Nitrate, existing as inorganic anions in water, possesses high water-solubility and has caused lots of contaminations around the world. It is thus extremely urgent to develop an effective method to effectively remove nitrate from water in a sustainable way. In this study, chitosan-ethylene glycol hydrogel (CEGH) was synthesized using the repeated freezing-thawing procedure. A range of batch sorption experiments were conducted to evaluate CEGH as a nitrate sorbent. The adsorption isotherms of nitrate onto CEGH followed the Langmuir model with coefficient of determination of 0.98 and a maximum Langmuir adsorption capacity of 49.04 mg/g, which is higher than that of other adsorbents. The adsorption of nitrate onto CEGH was affected by pH value and temperature. The results indicate that the main removal mechanism was polarity of CEGH molecules given by functional group O-H and N-H and hydrogen bond interaction between CEGH and nitrate molecules under acidic conditions. Therefore, CEGH, a biodegradable carbon-rich adsorbent, can be widely applied to remove nitrate in wastewater treatment and water body remediation.

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We examined the effects of a combination of slow-release urea (PCU) and common urea (PU) applied at different soil depths (0-30 cm soil layer) on inorganic nitrogen content, enzyme activity, and crop yield during two years (2017-2018) in a field experiment. There were eight treatments: CK (without N fertilizer); PU1(common urea applied at 5-10 cm deep soil layer); PU2(common urea applied at 5-10 cm deep soil layer, 60% seed fertilizer + 40% topdressing); PU3(20% common urea at 5-10 cm soil depth, 30% common urea at 15-20 cm soil depth, 50% common urea at 25-30 cm soil depth); PCU1(20% total nitrogen application rate at 5-10 cm soil depth, 30% total nitrogen application rate at 15-20 cm soil depth, 50% total nitrogen application rate at 25-30 cm soil depth), the N fertilizer at 5-10 cm was common urea, but, at 15-20 and 25-30 cm, it was a combination of PCU and PU at ratios of 3:7 and 3:7; PCU2 was as PCU1 but the ratio of PCU and PU was 5:5 at 15-20 cm and 5:5 at 25-30 cm; in PCU3, the ratio of PCU and PU was 3:7 at 15-20 cm and 5:5 at 25-30 cm; in PCU4, the ratio of PCU and PU was 5:5 at 15-20 cm and 3:7 at 25-30 cm. The results showed that PU1 could meet nitrogen demand at the 0-10 cm layer in the early growth stage compared with CK. PU2 and PU3 could meet nitrogen demand for 10-30 cm soil layer in the early stage of maize development. The combined application of slow release urea and common urea could meet nitrogen demand for the whole growth period of maize. In the filling and maturing period, combined application of slow release and common urea significantly increased not only NO3--N, NH4+-N, and alkali-hydrolyzed nitrogen contents but also urease and protease activities in the 10-20 cm and 20-30 cm soil layers compared with PU1-PU3. Compared with PU3, maize yield increased by 2.3%-24.6% and 1.3%-16.5% in the PCU1-PCU4 treatments in 2017 and 2018, respectively. PCU4 had the highest yield, with 13899 and 12439 kg·hm-2, respectively. Therefore, the combined application of slow-release and common urea at different soil layers could meet nitrogen demand in the early growth stage of maize and increase the content of inorganic nitrogen and enzyme activities in the 10-30 cm soil layers in the later growth period, which promoted the growth and increased the yield of maize. Among all the treatments PCU4 treatment was the most effective.

Persulfate activation by two-dimensional MoS2 confining single Fe atoms: Performance, mechanism and DFT calculations.

Developing efficient catalysts for persulfate (PS) activation is important for the potential application of sulfate-radical-based advanced oxidation process. Herein, we demonstrate single iron atoms confined in MoS2 nanosheets with dual catalytic sites and synergistic catalysis as highly reactive and stable catalysts for efficient catalytic oxidation of recalcitrant organic pollutants via activation of PS. The dual reaction sites and the interaction between Fe and Mo greatly enhance the catalytic performance for PS activation. The radical scavenger experiments and electron paramagnetic resonance results confirm and SO4- rather than HO is responsible for aniline degradation. The high catalytic performance of Fe0.36Mo0.64S2 was interpreted by density functional theory (DFT) calculations via strong metal-support interactions and the low formal oxidation state of Fe in FexMo1-xS2. FexMo1-xS2/PS system can effectively remove various persistent organic pollutants and works well in a real water environment. Also, FexMo1-xS2 can efficiently activate peroxymonosulfate, sulfite and H2O2, suggesting its potential practical applications under various circumstances.

Study on the influence of surface potential on the nitrate adsorption capacity of metal modified biochar.

Carbon materials, as effective adsorbents to numerous aqueous cationic contaminants, have been hardly applied to remove anions in wastewater. In this work, different modifying agents were used to modify corncob biochars (CC) and the surface potentials of these modified biochars were determined. Based on the findings, modification principle was determined to reveal the relationship between surface potentials of the biochars and their nitrate adsorption capacities. The surface potential was dominated by the metal cations and multivalent cations led to even positive zeta potential. The formation of metal oxide not only led to the augment in surface area but also increase the surface charge. FeCl3-modified biochar (Fe-CC) with the highest positive surface charge was utilized to remove anions (nitrate) from aqueous solutions. Characterization results confirm that Fe2O3 structure were successfully formed on biochar surface. This led to the formation of iron nitrate hydrate (Fe(NO3)3·9H2O), which enabled higher nitrate adsorption performance than that of pristine biochar. Batch experiments showed that nitrate adsorption on the Fe-CC was stable and almost independent of experimental pH and temperature. Based on the Langmuir model results, the maximum nitrate adsorption capacity of Fe-CC was 32.33 mg/g. Coexisting anions had negative influence on the adsorption performance. Findings of this work suggest that the modified biochar can be used in wastewater treatment to remove anions such as nitrate. Graphic abstract ᅟ.