Biochar In Order Research Articles

Evaluation of bamboo derived biochar as anode catalyst in microbial fuel cell for xylan degradation utilizing microbial co-culture

This study aimed to examine the microbial degradation of xylan through Bacillus sp. isolated from wastewater. Co-culture of Bacillus licheniformis strain and MTCC-8104 strain of Shewanella putrefaciens were employed in a microbial fuel cell (MFC) to facilitate energy production simultaneous xylan degradation under optimum conditions. Electrochemical properties of MFC and degradation analysis were used to validate xylan degradation throughout various experimental parameters. Degradation of the optimal xylan concentration using co-culture, resulting in a power density of 7.8 W/m3, the anode surface was modified with bamboo-derived biochar in order to increase power density under the same operational condition. Under optimum circumstances, increasing the anode's surface area boosted electron transport and electro-active biofilm growth, resulting in a higher power density of 12.9 W/m3. Co-culture of hydrolyzing and electro-active bacteria was found beneficial for xylan degradation and anode modifications enhance power output while microbial degradation.

Long Endurance Site-Specific Management of Biochar Applications Using Unmanned Aircraft Vehicle and Unmanned Ground Vehicle

Agricultural activities emit an increasing amount of carbon into the atmosphere, causing climate change. Carbon sequestration is one of the carbon-neutral technologies for reducing carbon emissions by spraying biochar in needed places, such as fertilizer places. It is critical to monitor carbon emissions and the use of biochar in order to properly manage carbon emissions. Prior methods, such as traditional soil or manure sample collection and semiautomatic analysis, are expensive and time-consuming, and they cannot make decisions in real time. We propose long-term, site-specific biochar application management using unmanned aircraft vehicles and unmanned ground vehicles equipped with proximity radar sensing. Our system takes the strategy that a UAV will land on a moving UGV to acquire long-range information with a reliable backup. Meanwhile, the UGV has many payload options to supply the UAV's sensing and actuation missions. We evaluated our system by using a simulated mission approach that contains the analysis of the controller for the landing sequence, and real-world vision-based landing marker tracking. Results show that our system achieves robustness landing control sequence and the error altitude calculation based on computer vision is less than ± 0.02 m on average.

The Impact of Biochar Used in Repairs to Historical Buildings on Public Health.

The subject matter of this manuscript concerns the analysis and identification of microorganisms that pose a threat to human health and, in particular, mold fungi occurring in historical buildings. Surfaces infected by fungal spores pose a threat to the structure and the health of both visitors to historical buildings and professionals working in them. Research was undertaken to fill in the defects in building partitions with a supplementary layer of biochar in order to eliminate, or partially reduce, the possibility of contamination with and development of harmful mold fungi. In the designed cement mixture, biochar was used as a filler, the task of which was to eliminate the causes that lead to the development of harmful mold fungi. Microbiological analyses of the surface of walls and air in selected buildings were carried out before and after the application of supplementary biochar layers. The inhibitory properties of the material used against the presence and growth of mold fungi were observed. The average number of microorganisms isolated on the tested partitions decreased by between 70 and 100%. As a consequence, the use of this material significantly influenced the air quality of the rooms, which is important for protecting the health of people at work, as well as those visiting historical buildings.

ADSORPTION STUDIES OF RHODAMINE B DYE FROM AQUEOUS SOLUTION USING ALKALINE MODIFIED BIOCHAR & NON MODIFIED BIOCHAR OBTAINED FROM THE PYROLYSIS OF MUNICIPAL SOLID WASTE

The aim of this research is to use Municipal Solid Waste (MSW) prepared from the pyrolysis at 450 ⁰C for the removal of cationic dye (Rhodamine B) in aqueous solution. The effects of contact time and reaction temperature were studied in a batch setup. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were used to characterize the modified Biochar and non modified Biochar in order to predict the morphological properties and structural modification respectively. It was found that initial dye concentration (10mg/L), adsorbent dosage (0.3g) and contact time (100minutes) were found to give the highest removal of dye from the adsorbents. Subsequently, it was observed that an increase in the reaction parameters showed an increasing trend for the removal of dye. SEM analysis showed distinct morphology for the fresh and spent adsorbent which was linked to potential clogging resulting from uptake of pore sites by the dyes. The adsorption isotherms showed that the adsorption equilibrium data obeys Langmuir adsorption Isotherm with the maximum monolayer adsorption capacity of 20.30 mg/g and 20.23 mg/g and Pseudo Second Order kinetic model best described the experimental findings for the two adsorbents used in the study. Moreover, thermodynamic study reveals that the adsorption is a spontaneous and exothermic process

Effects of various pyrolysis conditions and feedstock compositions on the physicochemical characteristics of cow manure-derived biochar

Pyrolysis, as a thermal decomposition process and environment-friendly technology, can be used for the safe treatment of cow manure. In this paper, the effects of pyrolysis conditions on the properties of biochar derived from different types of cow manure (i.e., fresh cow manure, flushing cow manure, and anaerobic fermentation residues) were studied using slow pyrolysis methods. The properties of feedstocks, thermal decomposition, and biochar were analyzed using elemental analysis, coarse fiber determination, TG–FTIR, ICP–MS, FTIR, XRD, and SEM–EDS. Results showed that the cow manure-derived feedstocks were rich in total organic C (>37%) and had no heavy metal risk. According to the results of TG–FTIR, pyrolysis produced more residual solids, CO, CH4, and NH3 and less CO2 than combustion. The factors affecting alkalinity, calorific value, adsorption capacity, and surface functional group properties of cow manure-derived biochar in order of effectiveness were as follows: pyrolysis temperature > manure characteristics > heating rate > residence time. In general, increasing the temperature from 300 °C to 700 °C increased the pH (8.05–11.74) and C content (45.75%–49.64%) of fresh cow manure biochar and decreased the yield (62.17%–39.82%), nutrient content (N + P + K = 6.90%–5.64%), iodine adsorption capacity (269–96 mg g−1), aromaticity, and polarity. The biochar derived from flushing cow manure and anaerobic fermentation residues had similar C content (>48%), alkalinity (pH > 10), calorific value (>20000 J g−1), stability, and polarity. Fresh cow manure biochar had higher nutrient recovery (6.6%) and iodine adsorption capacity (215 mg g−1) than others. Compared with flushing cow manure and anaerobic fermentation residues, the pyrolysis of fresh cow manure reduced nutrient loss and treatment energy consumption. This study provides a good basis for the optimization of the pyrolysis process of three typical kinds of cow manures in dairy farms.

Method of biochar application affects growth, yield and nutrient uptake of cowpea

Abstract Biochar produced from pyrolysis of organic materials has been found to improve plant growth by improving the physical and chemical characteristics of the soil as well as enhancing the sequestration of carbon dioxide that would release into the atmosphere through the decomposition of organic residues. However, there is scanty information on the methods used to apply biochar in order to optimize the benefits of biochar use for agricultural production. In view of this, a field study was carried out at the experimental field of CSIR – Soil Research Institute, Kumasi, to assess the effect of method of biochar application on the growth, yield and nutrient uptake of cowpea (Vigna unguiculata) in a moderately acidic sandy Ferric Acrisol. The experiment was set up using a Randomized Complete Block Design with three replications. The treatments imposed were as follows: control, broadcasting, spot and ring methods of application. The parameters assessed included growth and yield data as well as nitrogen and phosphorus uptake in shoots and grains. The data collected were subjected to analysis of variance using Genstat 12th edition. The results showed that the spot and ring methods of application significantly enhanced height, girth, nodule number and dry weight, shoot biomass and grain yield as well as nitrogen and phosphorus contents in shoots and grains when compared with the broadcasting method and control. This study therefore recommends the spot and ring methods of biochar application for adoption in cowpea production for enhanced growth, yield and nitrogen and phosphorus uptake.

Nutrient Loaded Biochar Doubled Biomass Production in Juvenile Maize Plants (Zea mays L.)

Biochars have long been associated with elevating plant productivity. An increasing number of studies, however, report that char application might also impair plant nutrient availability and reduce yields. In particular, char accompanying compounds as well as a hypothesized immobilization of nitrogen have been identified as playing a significant role in possibly diminishing plant productivity following char application. Herein, we tested the fertilizing effects of modified biochars in order to derive knowledge required to develop tailor-made chars, which predictably affect plant nutrition. Slow-pyrolysis maize cob biochar was modified by washing with either ethanol or hydrochloric acid to remove ash and organic compounds or by loading it with nutrient-rich residues in the form of digestate from the bioenergy sector. Maize plants were grown for 35 days on biochar-amended sand. We analyzed both substrate properties (pH, total carbon, and nitrogen, available magnesium and potassium) and plant functional traits (biomass, leaf area, root to shoot ratio, specific leaf area). Our results suggest that total plant biomass production remained unaffected by the application of biochar and its washed forms. Contrastingly, nutrient-loaded biochar induced a significant increase in productivity at similar nutrient levels due to improved plant nutrient uptake. Further research is required to understand the role of biochar modifications that facilitated improvements in plant productivity.

Evaluating the effect of different biochar application sizes on methane emission reduction from rice cultivation

Application of biochar to the soil has been reported as one of the mitigation technologies of CH4 emission from rice cultivation due to its unique characteristics of high porosity and surface area. The application of small particle size of biochar is rich in surface area that may enhance the mitigation potential. Rice cultivation and soil incubation experiments were conducted to evaluate the effect of two groups of biochar particle size on CH4 emission and production in order to show the mitigation potential. This experiment consists of three treatments including no biochar (CT), small particle size (0.5-2 mm) biochar (SB), and large particle size (2-4 mm) biochar (LB). Both biochar sizes were amended at 10 t ha−1 equivalent rate and all treatments were applied chemical fertilizer at 100 kg N ha−1 equivalent rate. The results demonstrated that SB and LB reduced cumulative CH4 emission by 24.0% and 17.1% and cumulative CH4 production by 24.6% and 15.0% as compared to CT, respectively. Our results showed that SB achieved higher mitigation potential than LB by an average of 8.47%, although it was not significant. The mitigation of both biochar sizes was supported by the significant change of soil methanogens and methanotrophs abundances. The suppression of methanogens abundance and the stimulation of methanotrophs abundance indicated in the ratio of mcrA to pmoA was significantly reduced in SB (68.0%) which higher than in LB (56.3%) as compared to CT. Both application sizes also increased soil oxidation capacity through soil Eh increase which no difference between SB and LB. In term of grain yield, SB and LB were not different and both did not show the significant change as relative to CT. The application of small size biochar in this study affected more mitigation potential of CH4 emission as compared to larger size, therefore there is a need of further study on typical size of biochar in order to recommend the most mitigation potential of biochar application.

BIOCARVÃO DO BIOSSÓLIDO DA ESTAÇÃO DE TRATAMENTO DE ESGOTO DE PRESIDENTE PRUDENTE-SP

Biosolidis a material rich in organic matter and other nutrients of agronomic importance such as nitrogen and phosphorus. Its end is almost always in landfills. Therefore, its transformation into biochar by the pyrolysis process would be a way to associate its inherent benefits to biochar, enabling a more appropriate final destination. Given this work the objective was to produce biochar in order to evaluate the viability of use in agriculture. The biochar was produced on a laboratory scale at different temperatures and therefore the characterization of the final product was performed. As a result, the material has proven to be rich in organic matter as temperature increases, thinning the material and increasing the specific surface making the alkaline pH serving as carbon sequestration. Thus, with the constant concern of sewage sludge 47Colloquium Exactarum, v. 11, n4, Out-Dez. 2019, p.46 –61. DOI: 10.5747/ce.2019.v11.n4.e296production, biochar proved to be more efficient than pure sewage sludge for agricultural application.

A novel clean production approach to utilize crop waste residues as co-diet for mealworm (Tenebrio molitor) biomass production with biochar as byproduct for heavy metal removal

Proper management of waste crop residues has been an environmental concern for years. Yellow mealworms (larvae of Tenebrio molitor Linnaeus, 1758) are major insect protein source. In comparison with normal feed wheat bran (WB), we tested five common lignocellulose-rich crop residues as feedstock to rear mealworms, including wheat straw (WS), rice straw (RS), rice bran (RB), rice husk (RH), and corn straw (CS). We then used egested frass for the production of biochar in order to achieve clean production. Except for WS and RH, the crop residues supported mealworms’ life activity and growth with consumption of the residues by 90% or higher and degraded lignin, hemicellulose and cellulose over 32 day period. The sequence of degradability of the feedstocks is RS > RB > CS > WS > RH. Egested frass was converted to biochar which was tested for metal removal including Pb(II), Cd(II), Cu(II), Zn(II), and Cr(VI). Biochar via pyrolysis at 600 °C from RS fed frass (FRSBC) showed the best adsorption performance. The adsorption isotherm fits the Langmuir model, and kinetic analysis fits the Pseudo-Second Order Reaction. The heavy metal adsorption process was well-described using the Intra-Particle Diffusion model. Complexation, cation exchange, precipitation, reduction, deposition, and chelation dominated the adsorption of the metals onto FRSBC. The results indicated that crop residues (WS, RS, RB, and CS) can be utilized as supplementary feedstock along with biochar generated from egested frass to rear mealworms and achieve clean production while generating high-quality bioadsorbent for environment remediation and soil conditioning.

Combining the microbial calcite precipitation process with biochar in order to improve nickel remediation

Microbially induced calcite precipitation (MICP) is a promising technology in the remediation of heavy metals, while biochar is a valuable adsorbent for its removal. In the present study, biochar was added to the MICP process to investigate its effect on the remediation of nickel (Ni). The MICP process immobilized 89% and 66% of Ni2+ at initial concentrations of 50 and 100 mg L−1, respectively. However, biochar had an inhibitory effect on the calcite produced by Bacillus cereus NS4 and suppressed the Ni remediation. The mechanism of suppression by biochar was elucidated by scanning electron microscopy-energy dispersion spectrophotometry, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. Biochar caused weakening of the adsorption bonds responsible for carbonate formation led to dissociation of the carbonate structure. This is the first study to combine biochar with the MICP process and provides reference data for better understanding of the mechanism of suppression of carbonate precipitation by biochar.

Poultry manure and sugarcane straw biochars modified with MgCl2 for phosphorus adsorption

Increases in agricultural productivity associated to the crescent use of finite reserves of phosphorus improved the demand for ways to recycle and reuse this nutrient. Biochars, after doping processes, seem to be an alternative to mitigate the large use of P reserves. Sugarcane straw and poultry manure were submerged in an MgCl2 solution in a 1:10 solid/liquid ratio and subsequently pyrolyzed at 350 and 650 °C producing biochar. Increasing concentrations of P were agitated with biochars in order to obtain the maximum adsorption capacity of P with the aid of Langmuir and Freudelich isotherm. MPAC was extracted, successively, with H2SO4 (0.5 mol L−1), NaHCO3 (0.5 mol l−1 a pH 8.5) and H2O, until no P was detected in the solution. Biochars without the addition of Mg did not have the ability to adsorb P but had this property developed after the doping process. The poultry manure biochar presented higher MPAC (250.8 and 163.6 mg g−1 of P at 350 and 650 °C, respectively) than that of sugarcane straw (17.7 and 17.6 mg g−1 of P at 350 and 650 °C, respectively). The pyrolysis temperature changed significantly the MPAC values for the poultry manure biochar, with an increase in the adsorbed P binding energy for both biochars. H2SO4 showed the best extraction power, desorbing, with a lower number of extractions, the greater amount of the adsorbed P. These materials doped with Mg and subjected to pyrolysis have characteristics that allow their use in P adsorption from eutrophic and wastewaters and therefore its use as a slow release phosphate fertilizer, indicating to be competitive in quality and quantity with available soluble chemical sources in the market.

Adsorption-assisted decontamination of Hg(ii) from aqueous solution by multi-functionalized corncob-derived biochar.

Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(ii) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (–COOH) on pre-oxidized biochar (BC–COOH). The maximum Hg(ii) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g−1, which was almost twice as that for pristine biochar (BC, 7.1 mg g−1). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual –COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(ii) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(ii) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.

Use of biochar as peat substitute for growing substrates of Euphorbia × lomi potted plants

Biochar from conifers wood was used in soilless culture as growing substrate alternative to peat for ornamental crops. Potted plants of Euphorbia × lomi Rauh cv. ‘Ilaria’ were grown with different mixtures (v:v) of brown peat and biochar in order to evaluate main physical and chemical characteristics of this biomaterial as well as its effect on plant growth, ornamental characteristics and nutrients uptake. Biochar addition to peat increased pH, EC and K content of the growing substrates, as well as air content and bulk density. Biochar content of substrates significantly affected plant growth and biomass partitioning: higher number of shoots and leaves, leaf area and leaf dry weight were recorded in plants grown in 40% peat-60% biochar, with respect to plants grown in 100% peat and secondarily in 100% biochar. Leaf chlorophyll content was higher in plants grown in 60% and 80% biochar, while biomass water use efficiency was higher with 60% biochar. Plant uptake of K and Ca increased as biochar content of the substrates increased. Hence, a growing substrate containing 40% brown peat and 60% conifers wood biochar was identified as the more suitable mixture allowing to have a high-quality production of Euphorbia × lomi potted plants.

The Effect of Low-Temperature Conversion of Plant Materials on the Chemical Composition and Ecotoxicity of Biochars

The chemical composition of biochars varies considerably depending on the chemical composition of biomass used for its production and conditions of the thermal conversion process. In the context of chemical composition, biochars are different from other types of organic matter in that they contain many more aromatic carbon compounds. The aims of this study were as follows: (1) to investigate the effect of pyrolysis process of plant material on the concentrations of macroelements, trace elements and polycyclic aromatic hydrocarbons (PAHs) in the biochars; (2) to evaluate the ecotoxicity of the biochars; (3) to integrate chemical and toxicity properties of biochars in order to assess their safe utilisation as fertiliser materials. It was found that the elemental composition, the contents of macronutrients and trace elements in biochars were determined by the type of converted biomass. In the case of contents of volatile elements, such as nitrogen and sulphur, the process conditions were of great importance. Among the analysed trace elements, only the cadmium content exceeded the limit value for premium class biochars. The process of thermal conversion of organic materials did not cause mobilisation of available forms of most of the studied trace elements. In the course of the study, it was found that the extracts from wheat straw biochar (WSB) were low-toxic, while the extracts from biochars derived from rape straw (RSB), Miscanthus straw (MSB), sawdust (SB), bark (BB) and leaves of trees (LTB) were highly toxic to V. fischeri. Based on the response of the test organism, the analysed biochars were arranged in the following order: WSB < BB < RSB < LTB < MSB < SB. The highest total content of PAHs (∑ 16 PAHs) was determined in rape straw biochar, and the lowest, in sawdust biochar. The studies revealed a negative correlation between the content of most of PAHs and inhibition of Vibrio fischeri luminescence.Graphical

Adsorption of ammonium on biochar prepared from giant reed

Giant reed was used as precursor for making biochar in order for the adsorption of NH4 (+)-N from aqueous solution. And the adsorption of the product to NH4 (+)-N was examined. The surface features of biochar were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), and X-ray diffraction (XRD). XRD patterns showed several peaks and correspond to the high amount of crystalline material. The crystals contain KCl, K2O, CaO, MgO, and SiO and possess high surface area which enhances adsorption. The influence of different parameters such as initial concentration, adsorption time, pH, and ionic strength has been carried out. The adsorption could reach equilibrium through 24h reaction and had the best adsorption amount at the solution pH values from 7 to 9. The cation has great influence on the adsorption of NH4 (+)-N, whereas the anion exerted a weaker effect. The adsorption followed pseudo-first-order and pseudo-second-order models. And the intraparticle diffusion and desorption studies further elucidated that the mechanism of adsorption on the product was ion exchange. The product equilibrium data was well described by the Langmuir and Freundlich model. The maximum adsorption capacities were 1.490mg/g. Biochar derived from giant reed at 500°C was suggested as a promising adsorbent for the removal of NH4 (+)-N from slightly polluted wastewater.

Effect of barley straw biochar application on greenhouse gas emissions from upland soil for Chinese cabbage cultivation in short-term laboratory experiments

Chinese cabbage was cultivated in upland soil with the addition of biochar in order to investigate the potential for reduction of greenhouse gas emissions. Barley straw biochar (BSB) was introduced in a Wagner pot (1/5000a) in amounts of 0 (BSB0, control), 100 (BSB100), 300 (BSB300), and 500 (BSB500) kg 10a-1. After the addition of BSB into the upland soil, carbon dioxide (CO2) emission increased while methane (CH4) and nitrous oxide (N2O) emissions decreased. The highest CO2 flux was measured for the BSB500 sample, (84.6 g m-2) followed by BSB300, BSB100, and BSB0 in decreasing order. Relative to those of control, the total CH4 flux and N2O flux for the BSB500 treatment were lower by 31.6% and 26.1%, respectively. The global warming potential (GWP) of the treatment without biochar was 281.4 g CO2 m-2 and those for treatments with biochar were in the range from 194.1 to 224.9 g CO2 m-2. Therefore, introducing BSB into upland soil to cultivate Chinese cabbages can reduce the global warming potential.

Recovery and electrochemical performance in lithium secondary batteries of biochar derived from rice straw.

Renewable biomass has attracted great attention for the production of biooil, biogas, and biochar, a carbon residual applicable for carbon sequestration and environmental remediation. Rice straw is one of the most common biomasses among agricultural wastes in South Korea. As part of our advanced and environmentally friendly research, we applied biochar derived from rice straw as the anode material for lithium-ion batteries (LIBs). Porous carbons with a high surface area were prepared from rice straw. Such porous carbons have exhibited particularly large reversible capacity and hence proven to be a candidate anode material for high-rate and high-capacity LIBs. Rice straw-derived biochars were synthesized at four different temperatures: 400, 550, 700, and 900 °C. The surface was modified by using HCl and H2O2 on the 550 °C biochar in order to increase the surface area. The resulting biochar was characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The surface area was measured by Brunauer-Emmett-Teller (BET) method. The electrochemical characterizations were investigated by galvanostatic charge-discharge (CD) curves, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). All samples exhibited reversible capacities of below 200 mAh g(-1). The surface-modified biochars exhibited improved cycle performance. Surface modification using HCl showed better cycle performance than H2O2. However, the capacities of the treated 550 °C biochar were similar to those of non-surface-modified biochar.

Ca and Fe modified biochars as adsorbents of arsenic and chromium in aqueous solutions

This work investigated the production of Ca and Fe modified biochars in order to use them for the removal of arsenic As(V) and chromium Cr(VI) from aqueous solutions. Rice husk was impregnated with CaO at an impregnation ratio 0.114, while both rice husk and the organic fraction of municipal solid wastes were impregnated with Fe0 and Fe3+ at impregnation ratios 0.114 and 0.23. The modified biochars exhibited high As(V) removal capacity (>95%), except for the case of rice husk impregnated with Fe0, whose removal capacity reached only 58%. All modified biochars exhibited much better As(V) removal capacity compared to the non-impregnated biochars. However, the Cr(VI) removal rates were not as high as the As(V) ones. The maximum Cr(VI) removal was observed in the case of rice husk biochar impregnated with 2.3% w/w Fe3+, whereas the majority of impregnation agents examined did not manage to enhance the biochars' Cr(VI) removal ability. The equilibrium study showed that the Freundlich model can adequately describe the sorption process for the majority of samples examined. Analysis of the amount of Fe present in the equilibrium solutions suggested that the main mechanisms of As(V) and Cr(VI) removal were possibly metal precipitation and electrostatic interactions between the modified biochars and the adsorbate.

Sorption of copper (II) and sulphate to different biochars before and after composting with farmyard manure

Biochar application has been suggested for reducing toxic levels of metals in contaminated soils and enhancing nutrient retention in agro‐ecosystems. We studied sorption of copper (Cu(II)) and sulphate‐sulphur (SO4‐S) to charcoal, gasification coke and flash‐pyrolysis biochar in order to relate sorption to char properties. Furthermore, we investigated the effect of composting of charcoal and gasification coke on sorptive properties. Langmuir sorption affinity coefficients for Cu(II) for non‐composted biochars increased in the order flash‐pyrolysis char &lt; charcoal &lt; gasification coke. The sorption capacity for Cu(II) of the chars decreased in the order gasification coke (629 mg kg−1) &gt; flash‐pyrolysis char (196 mg kg−1) &gt; charcoal (56 mg kg−1). Composting significantly increased the sorption affinity coefficient approximately by a factor of 5 for charcoal (up to 1.1 l mg−1) and by a factor of 3–4 for gasification coke (up to 3.2 l mg−1). Whereas Cu(II) sorption to gasification coke (composted or not) was largely irreversible, sorption to flash‐pyrolysis char and charcoal showed higher reversibility. Relationships between Cu(II) sorption and biochar properties such as cation exchange capacity, specific surface area or aromaticity suggest that sorption was largely determined by complexation with organic matter. Sorption of SO4‐S was negligible by non‐composted and composted biochars. Composted gasification coke might be suited to reducing toxic Cu(II) concentrations in contaminated soils. Composted charcoal can potentially improve Cu(II) retention in a plant available form in acidic, sandy soils with small organic matter contents. Transient effects of biochars on soil pH can over‐ride the influence of sorption to biochars on concentrations of trace elements in soil solution and their availability to plants.