Biochar Concentration Research Articles

Induced changes of pyrolysis temperature on the physicochemical traits of sewage sludge and on the potential ecological risks

Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS and SSB450 were in the moderate and considerable contamination ranges, respectively. For all pyrolysis temperature biochar Cd was the highest metal contributor to the PERI. Despite this, the potential ecological risk index of the SS and SSBs was graded as low.

Comparative study of biochar prepared from cow dung and sewage sludge and its application as an adsorbent for organic pollutants removal in water

AbstractIn this research, the synthesis of biochar from cow dung and sewage sludge and its application for the removal of organic contaminants using methylene blue (MB) as the model molecule was evaluated. Experiments were performed using different concentrations of adsorbent and MB and were optimized by a response surface methodology (RSM). Dynamic models were adjusted to the experimental data and the regeneration of the bed was studied. The results showed that the optimal conditions to favor the adsorption of MB, in a fixed bed and making a comparison between the two biochar sources, were those where an adsorbent biochar concentration of 5 g and initial MB concentration of 10 mg L−1 were used. The biochar prepared from cow dung presented the best adsorption conditions. Under these conditions, the breaking time was 172.73 min. The models of Thomas, Bohart–Adams, and Yoon–Nelson were applied for the study in fixed‐bed columns and it was observed that the models were adjusted satisfactorily. Regeneration was possible for three different cycles, slightly diminishing the performance of the bed with elution of HNO3. These results indicate that MB bed fixed adsorption on cow dung biochar is viable and suitable for water treatment.

Biochar: a low-cost adsorbent of Methylene Blue from aqueous solutions

Removal of Methylene Blue (MB) from aqueous solutions by compost-biochar and plant biomass-biochar mixtures is investigated under batch conditions to determine the adsorption capacity of biocarbons under variable parameters (initial Methylene Blue and biochar concentrations, temperature, pH of the solution). The experimental data have been computed using Freundlich adsorption isotherms. The adsorption percentage onto the biocarbons is shown to correlate linearly with the adsorbent quantity and concentration, MB-biochar contact time and pH. The results from the adsorption process are well correlated with the Freundlich model: R2 > 0.989 for compost-biochar and R2 > 0.977 for biomass-biochar. Biocarbons have been shown to be an effective and low-cost material for the removal of dye and colourisation from an aqueous solution.

Recovery of valuable metals from spent mobile phone printed circuit boards using biochar in indirect bioleaching

Improving the bioleaching efficiency of metals from spent mobile phone printed circuit boards (PCBs) in a short time has been of major interest in recent years. In this paper, a novel cheap catalyst (oak wood biochar) was used to improve the copper and nickel bioleaching efficiency from spent mobile phone PCBs. The biochar was derived from oak wood through slow pyrolysis at a low temperature of 500 °C for 1h. The results of RSM optimization indicated that the optimum conditions to maximize copper and nickel recovery were 1.6 g/L biochar and 16 g/L pulp density. The findings indicated that compared to without the presence of biochar, the leach yields of copper and nickel were high. As much as 98% of copper and 82% of nickel were leached by indirect bioleaching under optimum conditions. The better performance in the presence of biochar is due to both galvanic interactions between biochar and solid waste. The biochemical characterization of bioleaching solution suggested that the high concentration of biochar (> 1.6 g/L) led to copper absorption by functional groups on the surface of biochar. Compared to chemical leaching, the bioleaching has better performance. Under optimum conditions, the copper and nickel recovery by indirect bioleaching was 36% and 64% more than that by chemical leaching. Also, it is found that biochar has a positive effect on the chemical leaching process. Therefore, in this paper, the function of biochar was elaborated not only in bio-hydrometallurgy but also in the hydrometallurgy process.

Corn stover biochar increased edible safety of spinach by reducing the migration of mercury from soil to spinach

Mercury (Hg) is toxic and can affect human health through soil entering food chain. Spinach absorb easily heavy metals. Corn stover biochar can improve soil structure and physicochemical property. This study wanted to establish a Hg-corn stover biochar-soil-spinach model including 1 control group (without HgCl2 and corn stover biochar) and 24 treatment groups (with HgCl2 or/and corn stover biochar). Hg concentration was 0, 1, 2, 4, and 6 mg kg−1, respectively. Corn stover biochar contents were 0%, 1%, 3%, 5%, and 7% w/w, respectively. The results showed that residual Hg concentrations was the largest and water soluble and exchangeable Hg as well as carbonate bound Hg concentrations were the lowest among five Hg forms. Hg concentrations in four Hg treatment groups were higher than the control group in dose-dependent manner. The deposition of 6 mg kg−1 Hg was the highest. Corn stover biochar decreased Hg migration from soil to leaching solution and spinach, and passivation effect of 7% concentration of corn stover biochar was the best. Besides, corn stover biochar relieved the increase of methyl Hg caused by Hg in soil. Moreover, Hg concentration in roots was the highest and Hg concentration in stems was the lowest in spinach. Furthermore, Hg absorbed by roots was more than the sum of Hg absorbed by stems and leaves. In addition, we also found that the measured soil Hg concentrations were coincided with the predicted soil Hg concentrations under 1, 2, and 4 mg kg−1 Hg concentrations, except 2 mg kg−1 Hg at 7% C. Under 6 mg kg−1 Hg concentration, measured soil Hg concentrations was lower than that of the predicted soil Hg concentrations. Taken together, our findings indicated that corn stover biochar can increase edible safety of spinach by immobilizing Hg in soil and be used as an organic amendment.

Can biochar regulate the fate of heavy metals (Cu and Zn) resistant bacteria community during the poultry manure composting?

In this study, the influence of coconut shell biochar addition (CSB) on heavy metals (Cu and Zn) resistance bacterial fate and there correlation with physicochemical parameters were evaluated during poultry manure composting. High-throughput sequencing was carried out on five treatments, namely T1−T5, where T2 to T5 were supplemented with 2.5%, 5%, 7.5% and 10% CSB, while T1 was used as control for the comparison. The results of HMRB indicated that the relative abundance of major potential bacterial host altered were Firmicutes (52.88–14.32%), Actinobacteria (35.20–4.99%), Bacteroidetes (0.05–15.07%) and Proteobacteria (0.01–20.28%) with elevated biochar concentration (0%−10%). Beta and alpha diversity as well as network analysis illustrated composting micro-environmental ecology with exogenous additive biochar to remarkably affect the dominant resistant bacterial community distribution by adjusting the interacting between driving environmental parameters with potential host bacterial in composting. Ultimately, the amendment of 7.5% CSB into poultry manure composting was able to significantly reduce the HMRB abundance, improve the composting efficiency and end product quality.

Study on valorization of coconut (Cocos nucifera) husk into biochar for soil amendment and its effect on sorghum (Sorghum bicolor)

Biochar is one of the significant soil amendments. A lot of research has already done in the field of biochar. But very few studies have mentioned the effect of pyrolysis temperature on the plant growth. To the best of our knowledge we have not yet come across any systematic study elaborating the effect of various pyrolysis temperature of coconut husk biochar on seed germination and plant growth. Therefore, the experiment was conducted during 2019 to 20 at Institute of Chemical Technology, Mumbai, India to explore the effect of coconut husk biochar produced at various pyrolysis temperatures (300, 400, 500 and 600°C) individually and along with the nitrogen fertilizer (urea) on the growth of sorghum. Maximum biochar yield of 54.67 % was obtained at 300°C. The ash content, pH, and EC (electrical conductivity) of biochar significantly increased with increasing pyrolysis temperature, maximum ash content (31.4 %), pH (9.9) and EC (2.48 mS/cm) were observed at 600°C pyrolysis temperature. Bulk density and nitrogen concentration of biochar reduced with increasing pyrolysis temperature. Highest nitrogen concentration of 0.62% was detected in biochar produced at 300°C. Surface area of the biochar increased with an increase in the pyrolysis temperature giving a surface area of 213.91 m2/g at 600 °C pyrolysis temperature. The germination percentage was adversely affected by the use of biochar and nitrogen fertilizer combination treatment. Maximum shoot and root biomass of sorghum were obtained with the use of biochar produced at 300°C. Similarly, plant height, leaf area and stem diameter were significantly high in the treatment containing biochar obtained at 300°C pyrolysis temperature. Nevertheless, combining biochar and nitrogen fertilizer had no synergic and summative effect on sorghum growth. The findings of the present study thus demonstrate that biochar obtained at low pyrolysis temperature can be a practical approach to enhance crop biomass growth and possibly yield.

Use of biochar by sheep: impacts on diet selection, digestibility, and performance.

The objective of this study was to determine the influence of biochar obtained from exothermic production of lodgepole pine (Pinus contorta) and quaking aspen (Populus tremuloides) on sheep performance and diet digestibility and on preference for a ration enriched with this carbon-based material. Twenty-four lambs were housed in individual pens and assigned to one of three treatment groups (eight animals per group), where they received: 1) a 60:40 ration of alfalfa:barley (Control), 2) an isoenergetic and isonitrogenous ration with alfalfa, barley, and 2% biochar (BC), and 3) a simultaneous offer of the Control and BC rations (Choice). Lambs were exposed to two consecutive feeding periods (Period 1: 13 d and Period 2: 21 d), representing time intervals where the evolution of intake, animal performance, and rumen parameters were assessed; in vivo digestibility was determined during the last 5 d of the study. Ration intake did not differ among groups of lambs (P > 0.10), although during some days in Period 2, intake was greater for the BC and Choice groups than for the Control group (P < 0.05). Lambs in Choice had a lower preference for BC than for the Control ration (Period 1: P < 0.05; Period 2: P < 0.10), although they incorporated a substantial amount of BC (39 and 40%, for Periods 1 and 2, respectively) into their diets. No differences in body weight gains (ADG) or gain-to-feed ratios were found among groups of animals (P > 0.10), although dry matter digestibility and digestible dry matter intake was greater for lambs in the BC group than for lambs in Control group (P < 0.05). The ruminal concentration of the volatile acid acetate in Period 2 was greater for BC than for Choice (P < 0.05). During the same period, the concentration of valerate and ruminal pH values were greater in BC than in Control (P < 0.05). Thus, the addition of biochar to grain-based diets enhanced diet digestibility and influenced some ruminal parameters in lambs. Nevertheless, these positive effects were not reflected in significant improvements on ADG or feed conversion efficiencies. Lambs offered choices between Control and BC rations formed a diet with concentrations of biochar of ~1.2%, suggesting that these animals would tolerate such levels without reductions in ration palatability.

Poly(lactic acid) bio-composites containing biochar particles: Effects of fillers and plasticizer on crystallization and thermal properties

Biochar has emerged as a filler material for bio-degradable composites with favorable thermal and mechanical properties. Therefore, biochar is used in poly (lactic acid) (PLA) and PLA/thermoplastic starch (TPS) based composites. The crystallization and thermo-analytical properties of these blends with increasing amounts (20 to 50 wt%) of biochar are investigated. In the thermogravimetric analysis, the PLA/char composites’ onset degradation temperature and temperature of maximum weight loss decrease with increasing biochar concentrations (320 to 275 °C and 380 to 350 °C, respectively). Contrastingly, in the PLA/TPS/char composites, the impact of the biochar is shielded by the TPS. The unaltered glass transition demonstrates that biochar does not act as a plasticizer in any of the composites, while TPS does. Biochar acts as a nucleation agent, but hinders further crystal growth at high concentrations, as confirmed by isothermal crystallization and infrared spectroscopy. The TPS smoothens the PLA/biochar interface, leading to an obstructed nucleation effect of biochar, proven by differential scanning calorimetry, infrared spectroscopy, and scanning electron microscopy. This work demonstrates the shielding effect TPS has on biochar and can help to understand further and optimize the production and biodegradability of these composites.

The potential fertilizer value of Namibian beach-cast seaweed (Laminaria pallida and Gracilariopsis funicularis) biochar as a nutrient source in organic agriculture

Biochar has been reported as an efficient tool for carbon sequestration and soil quality improvement, though most research has evaluated the quality of biochar from terrestrial based materials. The study evaluated the macro; micro nutrients and heavy metal concentrations of biochar from seaweeds from Namibian coast. Seaweed species Laminaria pallida and Gracilariopsis funicularis were pyrolysed at different temperatures i.e. control (uncharred); 200; 400; 600 and 800 °C in order to determine the chemical and physical properties of the biochar produced. There were significant interactions (P < 0.05) between temperature and seaweed species on most parameters measured. A pyrolysis temperature of 400 °C resulted in an almost 50% reduction in biochar yield, with higher temperatures resulting in even more yield loss whilst producing biochar with higher alkaline pH above 7 and high EC above 20 mS/cm. G. funicularis biochar resulted in the highest macro element content with total C 38.3%; N 4.3% and P 6.3 g/kg, whilst L. pallida biochar had the highest contents of cations of 16.2 g/kg Ca; 6.4 g/kg Mg; 151 g/kg K and 45 g/kg Na. Higher pyrolysis temperatures did not result in consistent changes in total heavy metal content, with only Cd content being above the maximum permissible limits for biochar of 3.9 mg/kg. Generally, a pyrolysis temperature of 400°C was observed to give biochar with the best quality in terms of macro elements, pH and total C. G. funicularis biochar showed significantly higher nutrient concentrations, therefore has great potential in soil quality improvement.

Effect of terminal temperature on the morphology and potentially toxic metals concentrations of biochars derived from paper and kitchen waste

This study investigated the morphology and potentially toxic metal concentrations of paper waste-based biochar (PB) and kitchen waste-based biochar (KB) obtained at 500 and 700 °C. The morphology and potentially toxic metals (Cr, Mn, Cu, Cd, Pb, Zn, Ag, and Ba) concentrations in the biochars were determined by SEM and FT-IR analysis. The Cr, Mn, Cu, and Cd concentrations in PB were low, while the Ba content was relatively high at 0.1 mg∙kg−1. An increase in the terminal temperature led to an increase in the concentrations of Fe/Mn oxide-bound potentially toxic metals of PB, and a decrease in the concentrations of organic matter-bound potentially toxic metals. The Fe/Mn oxide-bound Cr, Mn, Cu, Pb, and Zn concentrations of KB decreased with an increase in the terminal temperature. Therefore, increasing the terminal temperature could reduce the bioavailability of potentially toxic metals in PB and KB. The environmental risk of the different biochars when used for soil remediation was assessed by the potential ecological risk index (RI), and a case study of a Tibetan soil was also conducted. The potentially toxic metal concentrations leached from both PB and KB were lower than the relevant standards. The findings showed that both PB and KB can be safely used for soil remediation.

Incorporation of biochar and nanomaterials to assist remediation of heavy metals in soil using plant species

Abstract Remediation of heavy metal-contaminated soils brings a techno-economical challenge for researchers and decision makers. The main purpose of this research is to study the co-application of nanoscale zerovalent iron (nZVI) and biochar (BC) to support remediation of cadmium contaminated soil using plant species. Plant seeds were exposed to various concentrations of nZVI and BC in the heavy metal-contaminated soil. Zero-valent iron nanoparticles were prepared using borohydride reduction method. Fresh urban yard trimmings were used to prepare BC at high pyrolytic temperature. Co-application of nZVI and BC enhanced plant germination and biomass establishment in contaminated soil. Concentration of cadmium in plant tissues increased with nZVI concentration, while application of BC enhanced immobilization of Cd in the soil. Inhibitory effect of the applied doses of nZVI on contaminant uptake by plants was not observed in this research. Integrated use of nZVI and BC significantly increased accumulation capacity of T. repens for cadmium with the greatest accumulation capacity of 1077.9 μ g per pot achieved in “300 mg/kg nZVI+2.5% BC” treatment (P

Sustainable and eco-friendly approach for phosphorus recovery from wastewater by hydrothermally carbonized microalgae: Study on spent bio-char as fertilizer

This study focuses on phosphorus recovery from simulated aqueous environment by hydrothermally carbonized microalgae biomass. A detailed study on parameters influencing adsorption such as time (10–60 min), temperature (10–60 °C), agitation speed (50–250 rpm) and bio-char concentration (0.3–1.5 g/L) was carried out. Batch studies showed a maximum 90 % phosphorus removal for a concentration of bio-char of 1.5 g/L, agitation speed of 150 rpm, temperature of 60 °C and at 60 min. The adsorption experimental data fitted well with Pseudo-first order kinetics and Langmuir isotherm models with correlation coefficient (R2) value of 0.99 and 0.97 respectively. According to Langmuir model, phosphorus and ammoniacal nitrogen adsorption capacity of bio-char was 2505 and 6.7 × e4 mg/g with least error. To avoid leaching of ammonia and phosphorus to atmosphere, the spent bio-char was activated with ammonia and phosphorus solubilizing bacteria and tested as fertilizer. Pot experiments performed with tomato plant showed that spent bio-char is an excellent fertilizer and comparable to commercial di-ammonium phosphate (DAP). The plants cultivated with spent bio-char fertilizer have reached an average height of 22 ± 0.5 cm and their chlorophyll contents were 24.5 ± 0.42 mg/g. This study provides a proof of concept and it can be extended to real time wastewater in future. This study is an example of sustainable approach towards recovery of valuable phosphorus from aqueous environment and using it as fertile soil amendment.

The role of rice husk biochar addition in anaerobic digestion for sweet sorghum under high loading condition

Biochar is a carbon rich product made from the biomass pyrolysis process. Recently, biochar addition in anaerobic digestion processes has attracted attention for its possible functions to act as pH stabilizing agent, microbial carrier, and interspecies electron transfer. In this study, the effects of rice husk biochar addition in sorghum anaerobic digestion were investigated in batch tests. Under high F/M (food to microorganism) ratio conditions, obvious pH decreases and volatile fatty acids (VFA) accumulation was observed. Addition of 15 g/L biochar was found effective to increase the sorghum maximum methane production rate by 25 % and shorten the lag phase time by 44 %. Further biochar concentration increase showed little effects. Alkalinity increase brought by biochar addition contributed to the performance enhancement. Moreover, the promotive effects of biochar addition on degradation of acetic acid, propionic and butyric acid were not obvious under neutral pH conditions.

Applying a new pomelo peel derived biochar in microbial fell cell for enhancing sulfonamide antibiotics removal in swine wastewater

A sequential anode-cathode double-chamber microbial fuel cell (MFC) is a promising system for simultaneously removing contaminants, recovering nutrients and producing energy from swine wastewater. To improve sulfonamide antibiotics (SMs)’s removal in the continuous operating of MFC, one new pomelo peel-derived biochar was applied in the anode chamber in this study. Results demonstrated that SMs can be absorbed onto the heterogeneous surfaces of biochar through pore-filling and π-π EDA interaction. Adding biochar to a certain concentration (500 mg/L) could enhance the efficiency in removing sulfamethoxazole, sulfadiazine and sulfamethazine to 82.44–88.15%, 53.40–77.53% and 61.12–80.68%, respectively. Moreover, electricity production, COD and nutrients removal were improved by increasing the concentration of biochar. Hence, it is proved that adding biochar in MFC could effectively improve the performance of MFC in treating swine wastewater containing SMs.

Activation of persulfate by biochar from spent malt rootlets for the degradation of trimethoprim in the presence of inorganic ions

AbstractBACKGROUNDAntibiotics such as trimethoprim (TMP) are used in large quantities and recent studies show that TMP is not eliminated completely in wastewater from municipal treatment plants. Advanced oxidation processes (AOPs), especially sulfate radical‐based AOPs, are highly reactive in the presence of a catalyst. Biochar, a green and low‐cost carbon material, is an excellent catalyst to degrade persistent pollutants. In this work, the degradation of TMP is studied using biochar from spent malt rootlets.RESULTSThe biochar has a specific surface area of 62 m2 g–1, point of zero charge 6.8, contains aromatics and is rich in –OH surface groups. The effect of sodium persulfate (SPS) (100–500 mg L–1), TMP (150–500 μg L–1), biochar (BC) concentration (45–180 mg L–1), solution pH (4–9) and water quality on degradation was investigated. The degradation rate increased with increasing SPS and BC concentration, decreasing TMP concentration and water matrix complexity, but remained insensitive to pH changes. Seven transformation products were identified and quantified, including hydroxylated and oxidized keto derivatives, and reaction pathways/mechanisms are proposed. The BC activation was coupled with low‐frequency ultrasound (20 kHz), which plays a synergistic role in degradation, but not when coupled with simulated solar irradiation.CONCLUSIONThe occurrence of various ions in bottle water (BW) impact negatively TMP degradation and so does the existence of organic matter in treated wastewaters. The studied reaction seems to be a surface process where the biochar serves as a platform to generate sulfate and –OH radicals, as well as an electron transfer mediator. © 2020 Society of Chemical Industry

Degradation of sulfamethoxazole with persulfate using spent coffee grounds biochar as activator

In the present study, biochar from spent coffee grounds was synthesized via pyrolysis at 850 °C for 1 h, characterized and employed as catalyst for the degradation of sulfamethoxazole (SMX) by persulfate activation. A variety of techniques, such as physisorption of N2, scanning electron microscopy, Fourier transform infrared spectroscopy, X–ray diffraction, thermogravimetric analysis, and potentiometric mass titration, were employed for biochar characterization. The biochar has a surface area of 492 m2/g, its point of zero charge is 6.9, while mineral deposits are limited.SMX degradation experiments were performed mainly in ultrapure water (UPW) at persulfate concentrations between 100 and 1000 mg/L, biochar concentrations between 50 and 200 mg/L, SMX concentrations between 500 and 2000 μg/L and initial solution pH between 3 and 10. Real matrices, besides UPW, were also tested, namely bottled water (BW) and treated wastewater (WW), while synthetic solutions were prepared spiking UPW with bicarbonate, chloride, humic acid or alcohols. Almost complete removal of SMX can be achieved using 200 mg/L biochar and 1000 mg/L sodium persulfate (SPS) within 75 min. The presence of biochar is important for the degradation process, while the activity of the biochar increases linearly with SPS concentration. Degradation follows a pseudo–order kinetic model and the rate increases with increasing biochar concentration and decreasing SMX concentration. Although SMX adsorption onto the biochar surface is favored at acidic conditions, degradation proceeds equally fast regardless of the initial solution pH. Reactions in either real matrix are slower, resulting in 55% SMX removal in 60 min for WW. Bicarbonate causes severe inhibition as only 45% of SMX can be removed within 75 min in UPW. The addition of alcohol slightly inhibits degradation suggesting that the reaction pathway is either under electron transfer control or due to the generation of surface oxygen radicals with higher oxidation potential than the homogeneously produced radicals.

Biocidal Activity of Fast Pyrolysis Biochar against Escherichia coli O157:H7 in Soil Varies Based on Production Temperature or Age of Biochar

Soils in which fresh produce is grown can become contaminated with foodborne pathogens and are sometimes then abandoned or removed from production. The application of biochar has been proposed as a method of bioremediating such pathogen-contaminated soils. The objectives of the present study were to evaluate three fast-pyrolysis-generated biochars (FPBC; pyrolyzed in house at 450, 500, and 600°C in a newly designed pyrolysis reactor) and 10 United Kingdom Biochar Research Center (UKBRC) standard slow-pyrolysis biochars to determine their effects on the viability of four surrogate strains of Escherichia coli O157:H7 in soil. A previously validated biocidal FPBC that was aged for 2 years was also tested with E. coli to determine changes in antibacterial efficacy over time. Although neither the UKBRC slow-pyrolysis biochars or the 450 and 500°C FPBC from the new reactor were antimicrobial, the 600°C biochar was biocidal (P < 0.05); E. coli populations were significantly reduced at 3 and 3.5% biochar concentrations (reductions of 5.34 and 5.84 log CFU/g, respectively) compared with 0.0 to 2.0% biochar concentrations. The aged 500°C FPBC from the older reactor, which was previously validated as antimicrobial, lost efficacy after aging for 2 years. These results indicate that the biocidal activity of FPBC varies based on production temperature and/or age.

The use of biochar for controlling acid mine drainage through the inhibition of chalcopyrite biodissolution

Although chalcopyrite biodissolution plays an important role in the formation of acid mine drainage (AMD), the control of AMD through inhibiting the biodissolution of chalcopyrite has not been studied until now. In order to fill this knowledge gap, a novel method for inhibiting chalcopyrite biodissolution using biochar was proposed and verified. The effects of biochar pyrolysis temperature and biochar concentration on the inhibition of chalcopyrite biodissolution in the presence of Acidithiobacillus ferrooxidans (A. ferrooxidans) were studied. The results indicate that biochar significantly inhibited chalcopyrite biodissolution, thus reducing the number of copper and iron ions and quantity of acid released. In turn, this suggests that AMD generation was suppressed under these conditions. Biochar pyrolyzed at 300 °C (Biochar-300 °C) was the most effective at inhibiting chalcopyrite biodissolution and reduced its biodissolution rate by 17.7%. A suitable concentration of biochar-300 °C enhanced its inhibition of chalcopyrite biodissolution. The optimal concentration of biochar-300 °C for inhibiting chalcopyrite biodissolution was 3 g/L. Biodissolution results, cyclic voltammetry, mineral surface morphology, mineralogical phase, and elemental composition analyses reveal that biochar inhibited the biodissolution of chalcopyrite by promoting the formation of passivation layer (jarosite and Sn2−/S0) and adsorbing bacteria.

Sonochemical degradation of propylparaben in the presence of agro-industrial biochar

Abstract The degradation of propylparaben (PP) by 20 kHz ultrasound irradiation in the presence of biochar was investigated. The biochar was produced from rice husk and characterized exhaustively by several techniques. It contains high percentage of stable, amorphous carbon with a considerable number of aromatic moieties and about 60 % of ash content, exhibits a specific surface area of 70.6 m2/g and has a slightly basic surface with a pzc around 8. Batch experiments were performed with a horn-type sonicator, mainly in ultrapure water (UPW), while actual matrices such as bottled water, groundwater and treated wastewater were also tested to assess the effect of water constituents on degradation. The simultaneous use of ultrasound and biochar had a synergistic effect on PP degradation relative to the individual processes, i.e. silent adsorption and irradiation without biochar, resulting in about 60 % synergy. The pseudo-first order rate increased with increasing power density and biochar concentration (up to a certain value) and decreasing temperature and PP concentration, while basic or acidic conditions retarded degradation. Higher PP concentrations resulted in lower rate constants, thus pointing out that the production of radicals was the rate-determining step. Reactions in actual matrices were slower than in UPW (i.e. up to ten times) and this was ascribed to the various inorganic (i.e. bicarbonate, chloride) and organic (i.e. humic acid analogues) water constituents.