Surface Area Of Biochar Research Articles

Malachite green adsorption from aqueous solutions onto biochar derived from sheep manure: adsorption kinetics, isotherm, thermodynamic, and mechanism

The adsorption of Malachite Green (MG) from aqueous solution was achieved using biochar derived from sheep manure pyrolyzed at 450 °C. Sheep manure biochar was characterized before and after adsorption of MG by SEM and FTIR. In addition, surface area measurement was performed by BET surface area and pore analyzer. The influence of contact time, pH, dose, temperature, and initial MG concentrations on the adsorption of MG onto sheep manure biochar (SMB) was investigated in experiments. Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich isotherm models were used to analyze the data. Results assumed best fitting model is Langmuir isotherm model (R 2 value 0.99). Mean free adsorption energy (E) was obtained 94.71 kJ mol−1, R L value was between 0.013 and 0.14. That indicates monolayer, favorable, and physisorption adsorption, as well as an endothermic adsorption process. Maximum uptake value from Langmuir model obtained 208.33 mg g−1. Surface area of SM biochar was 11.731 m2 g−1. NOVELTY STATEMENT This study is the first study on the adsorption of malachite green dye substance on sheep manure derived biochar. A natural and cheap adsorbent with high dye removal, such as 208,33 mg g−1. A guiding study for the conversion of agricultural waste into products with highly added value.

Removal of Cr(VI) from aqueous solution by biochar derived from rice husk

In this work, biochar produced from Indonesian rice husks. Then used as adsorbent of Cr(VI) in aqueous solution. The XRD pattern of biochar showed the characterization pattern at 23º (002) reflection, appearance of silicate oxide, and the carbon vibrations. The surface area and SEM morphologies confirmed that after pyrolysis treatment the surface of rice husk has changed. The surface area of biochar increased after thermal treatment. The adsorption study of Cr(VI) by biochar demonstrate 2nd-order reaction, and Langmuir isotherm models. The maximum adsorption capacity of biochar derived rice husk to adsorb Cr(VI) is 161.290 mg/g, and biochar showed the good potential as reuseable adsorbent to remove heavy metal in aqueous solution.

Effects of different pretreatment methods on biochar properties from pyrolysis of corn stover

To explore the effects of pretreatment methods including drying, vacuum freezing drying (VFD), pelleting, and ultrasonic vibration-assisted pelleting (UV-AP) on corn stover and biochar properties, the physicochemical and morphological changes of biomass before and after pretreatment were examined, and the effects of different pretreatment methods on biochar properties were investigated. The results showed that different pretreatment methods have a significant effect on the surface and internal structure of biochar. The highest and lowest specific surface area, micropore area, and total pore volume of biochar were 25.84 m2/g, 9.27 m2/g, 0.53 cm3/g, and 17.33 m2/g, 4.39 m2/g, 0.29 cm3/g, respectively. FTIR analysis showed that the functional group of pretreated corn stover was similar to those of biochar. Ultimate analysis indicated that both pretreatment methods and the highest treatment temperature had a significant effect on biochar compositions. The order of carbon content of biochar derived from different pretreatment methods was drying > VFD > UV-AP > pelleting. The biochar yield, enhancement factor, and energy yield were significant affected by pretreatment methods. By contrast, the biochar pH was alkaline and not significantly affected by pretreatment methods. These findings provide a reliable route to choose pretreatment methods for producing biochar with desired properties, which could be a guide for industrial application.

Sustainable valorization of sugarcane leaves for succinic acid and biochar production

The leaves of sugarcane (Saccharum officinarum) are agricultural waste that is burnt before harvesting. This project aims to find an alternative way to increase the value of sugarcane leaves and decrease air pollution by using the leaves as raw material to produce succinic acid and biochar. Reducing sugars were extracted from the leaves by H2SO4 hydrolysis. The sugars were then fermented by Yarrowia lipolytica TBRC 4417 to produce succinic acid. The solid residue was used as the raw material for biochar production by pyrolysis. The effects of pyrolysis temperature (350, 400, and 450℃) and nitrogen gas flow rate (5, 10, and 15 Lmin-1) on the specific surface area of biochar were determined. The adsorption capacity of mixed nitrogen, phosphorus, and potassium compound solution at various concentrations by biochar was also investigated. The hydrolysis condition was at 1%v/v of H2SO4, 100 gL-1 of sugarcane leaves, and hydrolysis time of 60 min. The hydrolysate yielded sugar monomers at a concentration of ca. 13.00 gL-1 of xylose and 2.00 gL-1 of glucose. The fermentation process of extracted reducing sugar from sugarcane leaves by Yarrowia lipolytica TBRC 4417 was studied at 30℃ for 84 h. with 120 rpm shaking. It was found that Yarrowia lipolytica TBRC 4417 produced succinic acid in glucose, mixed glucose and xylose, and extracted reducing sugars. The maximum succinic acid yield of 0.061 g succinic acid /g sugar consumption was obtained. For biochar production, the maximum specific surface area of 301.19 m2g-1 was found at a pyrolysis temperature of 400℃ and the N2 gas flow rate of 10 Lmin-1. The maximum adsorption capacity of the mixed solution was 28.45 wt%. The adsorption capacity of biochar was N>P>K at a total concentration of 100 mgL-1. This study demonstrates the agricultural waste's potential value as a useful feedstock for the biological generation of succinic acid and biochar.

Production of activated biochar via a self-blowing strategy-supported sulfidated nanoscale zerovalent iron with enhanced reactivity and stability for Cr(VI) reduction

Biochar-supported nanoscale zero-valent iron (nZVI) has been unitized for the reduction of Cr(VI). However, the low specific surface area of biochar and the surface oxidation of nZVI limit its contaminant removal efficiency. In this study, activated biochar (ABC) was prepared through a self-blowing strategy and was used as a supporter for sulfidated nZVI (S-nZVI@ABC). The results revealed that S-nZVI@ABC had a significantly increased specific surface area (414 m2 g−1) as compared to S-nZVI supported on commercial biochar (S-nZVI@BC, 62 m2 g−1), and the S-nZVI particles were evenly dispersed. Compared with S-nZVI@BC, the reactivity S-nZVI on ABC increased by 23%. The removal efficiency of Cr(VI) by S-nZVI@ABC was also much higher than the content removed by nZVI, nZVI@ABC. The removal efficiency was nearly doubled when the S/Fe was increased from 0 to 0.5. Higher dosage, lower pH value and Cr(VI) concentration led to an increased Cr(VI) removal efficiency. The retention rate of Cr(VI) removal efficiency was higher than 90% after 10 days of aging. S-nZVI@ABC also showed good reusability in the recycling experiment. The removal process of Cr(VI) was classified as an endothermic process and fitted with the Langmuir adsorption isotherm. Multiple interaction mechanisms including reduction, precipitation, and adsorption were involved in the removal of Cr(VI) by S-nZVI@ABC.

Porous biochar derived from tea saponin for supercapacitor electrode: Effect of preparation technique

Biochar is widely employed as an electrode of supercapacitor. In this work, one-step pyrolysis and chemical activation method were introduced to prepare porous biochars from tea saponin (TS). The performance differences of biochars prepared by two methods were studied. On this basis, further researches were carried out to explore the influence of the mass ratio of KOH/pre-carbonized precursor on the structure and electrochemical performance of the biochars. All samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results revealed that KOH could effectively increase the specific surface area of biochar. The specific area of ACTS-1.0 prepared with a KOH/pre-carbonized precursor mass ratio of 1:1, is up to 1550.03 cm2/g with a pore volume of 0.9076 cm3/g, and the structure was highly amorphous and disordered. The FT-IR and XPS results showed that there are various functional groups on the ACTS-1.0 biochar surface. These structural and compositional advantages lead to a higher specific capacitance (278 F/g) of ACTS-1.0 in an aqueous electrolyte and a high energy density of 27.01 Wh/kg at an organic electrolyte. Meanwhile, the as-prepared ACTS-1.0 has excellent cycling stability over 10,000 cycles in various electrolytes.

New Separation Material Obtained from Waste Rapeseed Cake for Copper(II) and Zinc(II) Removal from the Industrial Wastewater.

Rapeseed cake biochar was produced by pyrolysis at 973.15 K for 2 h, in anoxic conditions. Porous structure, specific surface area and die composition of waste rapeseed cake were studied. The specific surface area of rapeseed cake biochar was 166.99 m2·g−1, which exceeded most other biochars reported, which made it an attractive material during wastewater treatment. The SEM study of the material demonstrated a large number of pores formed on the cell wall, with a pore volume Vp = 0.08 cm3·g−1. The results indicate lower aromaticity and increased polarity of the tested material. The observed H/C ratio of 0.29 is similar for activated carbons. Furthermore, sorption properties of the obtained carbon material in relation to copper(II), zinc(II) and arsenic(III) ions were also studied. Moreover, the impact of parameters such as: sorption time, temperature, adsorbate concentration, sorbent mass and solution pH on the efficiency of the adsorption process of the studied cations was also examined. Sorption studies revealed that the sorbent can be successfully used for the separation of Cu(II) and Zn(II) from technological wastewaters. Rapeseed cake biochar exhibits superior Cu(II) adsorption capacity (52.2 mg·g−1) with a short equilibrium time (6 h). The experimental data collected show a high selectivity of the obtained carbon material relative to copper(II) and zinc(II) ions in the presence of arsenic(III) ions.

Enhanced heavy metals sorption by modified biochars derived from pig manure

To enhance the sorption efficiency of heavy metals by modified biochar, biochars derived from pig manure at different pyrolyzing temperatures (300 °C, 500 °C and 700 °C) were oxidized and thiolated using H2O2 and 3-mercaptopropyltrimethoxysilane, respectively. The physicochemical properties of biochars and sorption kinetics, isotherms, and mechanisms for Pb and Cd were studied. Oxidation and thiolation decreased the aromaticity and ash content, and increased the polarity and the specific surface area and pore volume of biochars. Oxidation introduced oxygen-containing functional groups into biochars, and the oxidation reaction took place at CC bonds. The thiolation of oxidized biochar prepared at moderate-temperature had the highest sulfur content (4.43%) due to that this biochar was rich in oxygen-containing groups, which can act as the active sites for thiol groups loading. Sorption capacity of biochars for heavy metals increased by 2.58–4.22 times with the increase of pyrolyzing temperature, except the original biochar prepared at moderate-temperature, which had the highest Pb sorption capacity. The distribution coefficient of heavy metals onto modified biochars was enhanced by up to 85.4%. Oxidization treatment was more suitable for immobilization of low concentrations of Cd onto low- and moderate-temperatures biochars, while thiolation treatment was more suitable for immobilization of high concentrations of heavy metals. The sorption of heavy metals by biochars occurred via cation exchange, precipitation, cation-π EDA interactions and complexation. The contribution percentage of complexing with functional groups increased after modification. The results suggest that oxidization and thiolation treatments of animal manure biochars are promising methods for the treatment of heavy metals polluted environment.

Porous biochar purification method from coconut shell by alkali roasting followed by leaching and its application as a lithium primary battery

The electrochemical performance of coconut shells biochar can be improved as a Lithium primary battery by increasing its purity. Biochar was synthesized by pyrolysis under N2 atmospheric conditions at a temperature of 500°C for 5 hours. The methods to purify biochar were the alkaline roasting method to reduce silica content and the leaching method at room temperature using 10% w/w H2SO4 to reduce metal oxide content. The used alkaline substance was 45% w/w NaOH solution under process temperature, which varied between 200-350°C with increasing the pressure. Energy-dispersive X-ray results show that biochar’s carbon purity increased from 90.18% w/w to 97.41% w/w at the alkaline roasting temperature of 300°C. The surface area of biochar is also increased from 782,112 m2/gram to 1218,646 m2/gram at the same temperature. Electro Impedance Spectroscopy test shows charge transfer and semi-infinite diffusion, which can be explained by the diffusion of Li+ ions from LiClO4 solution to purified biochar at the cathode. The charge transfer resistance value in purified biochar is less than in biochar that has not been purified. The discharge performance test shows that lithium primary batteries’ capacity increases along with biochar purity. The highest capacity of biochar is 126.21 mAh/gram at 300°C.

Synthesis and Characterization of Adsorbent Biochar/MnFe2O4 Composite from Agricultural Residue for Wastewater Treatment

Agriculture residue is produced every year in millions of tons worldwide and can be used as cheaper and environmentally friendly adsorbent. Herein, the biochar was synthesized by pyrolysis from coconut hull, corncob, rice husk, peanut hull and wheat straw. Total organic carbon was determined by standard TC-IC method, i.e., for Wheat Straw was found 20% highest among others agricultural residue and selected for biochar/MnFe2O4 composite synthesis. FTIR spectroscopy showed a band at 630 cm−1 that confirms the presence of MnFe2O4. BET surface analysis data showed the average specific surface area of biochar in the range of (4.3–79.389 m2 g−1). The surface area of biochar/MnFe2O4 composite was 149.96 m2 g−1, which was highest of all synthesized biochar’s. Adsorption study was carried out by using a specified amount of biochar for the specified time in a 50 ml wastewater sample of known chemical oxygen demand (COD) value. Biochar/MnFe2O4 adsorbent composite showed greater COD reducing the capacity of 70% than that of biochar produced without the formation of precipitates of MnFe2O4. The combination of various appealing attributes including cost-effective, environmentally friendly, and good COD reducing ability makes adsorbent a good option to be used in industrial applications specifically in the field of water treatment.

The effects of biochars produced in different pyrolsis temperatures from agricultural wastes on cadmium uptake of tobacco plant.

Abiotic stresses caused by cadmium (Cd) contamination in soil retard plant growth and decline the quality of food. Amendment of biochar was reported effective in reduction of mobility, plant uptake and toxicity of Cd in plants. The aim of this study was to investigate the effect of biochar applications produced from corn cob and rice husk at three different pyrolysis temperatures (400, 500 and 600 °C) on Cd uptake of tobacco plants. The results showed that the shoot Cd concentration and content of tobacco plants significantly increased with the application of Cd in increasing doses. The results showed that increasing Cd dosescaused significant increase (P < 0.01) in shoot Cd concentration and content of the tobacco plant at three different pyrolysis temperatures of both corn cob and rice husk biochars. The concentration of Cd was 0.48 mg kg−1 in Cd0 dose of corn cob biochar produced at 500 °C and increased to 61.6 mg kg−1 at Cd5, while Cd concentration increased to 72.3 mg kg−1 with rice husk biochar. Despite the increase in Cd concentrations and content, shoot Cd concentrations and contents were significantly (P < 0.01) reduced with the treatments of corn cob and rice husk biochars produced at different pyrolysis temperatures. The Cd concentration at Cd5 dose in the absence of biochar addition was 90.5 mg kg−1, while Cd concentration at Cd5 dose in 400, 500 and 600 °C treatments of corn cob biochar was reduced to 66.5, 61.6 and 67.3 mg kg−1 respectively, and to 77.0, 72.3 and 70.2 mg kg−1 in rice husk biochar. The results also revealed that corn cob biochar treatments were more effective in reducing Cd uptake of tobacco plants compared to rice husk biochar. Higher specific surface area of corncob biochar compared to rice husk biochar caused to the difference between two biochar sources on Cd uptake of tobacco plants.

Miscanthus biochar value chain - A review

To complete a loop of the Miscanthus value chain including production, phytomanagement, conversion to energy, and bioproducts, the wastes accumulated from these processes have to be returned to the production cycle to provide sustainable use of the feedstock, to reduce costs, and to ensure a zero-waste approach. This can be achieved by converting Miscanthus feedstock into biogas and biochar using pyrolysis and then returning biochar to the production cycle of Miscanthus crop applications in the phytotechnology of trace elements (TEs)-contaminated/marginal lands. These processes are subjects of the current review, which focused on the peculiarities of biochar received from Miscanthus by pyrolysis, its properties, the impact on soil characteristics, the phytoremediation process, biomass yield, and the abundance of soil biodiversity. Results from the literature indicated that the pH, surface area, and porosity of Miscanthus biochar are important in determining its impact on soil characteristics. It was inferred that the most effective Miscanthus biochar was produced with a pyrolysis temperature of about 600 °C with a residence time from about 30 min to an hour. Another important factor that determined the impact of Miscanthus biochar on soil health is the application rate: with its increase, the effect became more essential, and the recommended rate is between 5% and 10%. The influence of Miscanthus biochar on the TEs phytoremediation parameters is less studied, generally Miscanthus biochar produced at higher temperatures and added with higher application rates is more likely to restrict the mobility and availability of TEs by different plants. However, some published results are contradictory to these conclusions and showed absence of significant difference in TEs reduction during application of different Miscanthus biochar doses. The future experimental studies have to focus on determining the impact of a technological pyrolysis regime on Miscanthus biochar properties on TEs-contaminated or marginal land when biochar will be obtained from contaminated rhizomes and waste after the application of phytotechnology. In addition, studies must explore the influence of this biochar on TEs phytoparameters, enhancements in biomass yield, improvements in soil parameters, and the abundance of soil diversity.

Enhanced adsorption of polystyrene nanoplastics (PSNPs) onto oxidized corncob biochar with high pyrolysis temperature

Plastic pollution has become a global threat in the natural environment, and an urgent remedial measure is needed to reduce the negative effects caused by plastic pollutants. In the current study, the effects of pyrolysis temperature (500 °C, 700 °C, and 900 °C) and aging on the adsorption of polystyrene nanoplastics (PSNPs) onto corncob biochar were systematically assessed with kinetic, isotherm, pH-dependent adsorption experiments, FTIR and XPS spectroscopy, and DLVO calculations. The oxidation was done with 5% of HNO3/H2SO4 to simulate long-term oxidative aging of biochar in the environment. The results showed that the specific surface area, hydrophobicity, and aromaticity of biochar increased with pyrolysis temperature, whereas the specific surface area and amounts of oxygen-containing groups increased after oxidation. The adsorption mechanism of PSNPs onto the biochar was explored based on the correlation between biochar properties and adsorption parameters derived from adsorption isotherms. Overall, the adsorption capacity of biochar for PSNPs increased with increased pyrolysis temperature and after aging. While the increase of specific surface area was considered the major factor leading to the increase of the adsorption, the variation in surface properties also played an important role. Pore filling, hydrophobic interaction, and hydrogen bonding may all be involved in PSNPs adsorption to biochar. However, the hydrophobic interaction might be more important for the fresh biochar, whereas hydrogen bonding involving oxygen-containing groups might make a bigger contribution to PSNPs adsorption to oxidized biochar. The pH experiments revealed that PSNPs adsorption decreased in general with the increase of pH, indicating that electrostatic repulsion played a vital role in the PSNPs adsorption process. The results of this study indicate that biochar can be potentially applied to immobilize plastic particles in terrestrial ecosystems such as in soil or groundwater, and the immobilization could be enhanced via artificial oxidation or aging of biochar in the natural environment.

Biochar production by coconut shell gasification in supercritical water and evolution of its porous structure

Biochar produced by pyrolysis is more and more widely applied in industrial and agricultural fields. The properties of biochar depend largely on its pore structure. Supercritical water has special physical and chemical properties, and may result in unique evolution rule of pore structure during the gasification process. In this paper, supercritical water gasification (SCWG) experiment of coconut shell was conducted, and porous structure in biochar was characterized. The results showed that micropores were formed and enlarged during the SCWG process; size of mesopores focused on 12 nm and 41 nm, and its content increased with time. Specific surface area of biochar increased first then decreased, and the peak value reached 279.3 m2/g at 30 min, 78 times higher than that of raw material. As for pore volume, it almost increased continually throughout the gasification process and up to 0.32 m3/g at 60 min, 43 times higher than raw material.

Enhanced adsorption capacity of tetracycline on tea waste biochar with KHCO3 activation from aqueous solution.

Activation is an important pathway that can enhance the adsorption capacity of biochar. In this study, a modified tea waste biochar (MTWBC) was prepared via a two-step pyrolysis approach with KHCO3 activation. Pristine tea waste biochar (TWBC) was also produced as control via one-step pyrolysis without activation. Various characterizations were undertaken to investigate the influence of modification on the morphology, composition, carbon structure, surface area, and functional group of biochar, including scanning electron microscope (SEM), surface area and pore analyzer, element analysis, point of zero charge (pHPZC), X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). After KHCO3 activation treatment, the surface area, total pore volume, and micropore volume of MTWBC reached 1981 m2·g-1, 0.8547 cm3·g-1, and 0.6439 cm3·g-1 which were 7.34-fold, 7.27-fold, and 7.30-fold increases, respectively, compared with TWBC. The aromaticity, hydrophilicity, and polarity of the MTWBC increased after modification. More graphitization with less defective structures occurred in MTWBC after modification. The C-, O-, and N-containing groups in MTWBC also changed after the reaction of KHCO3. The pseudo-second-order and Freundlich models best described the adsorption process on biochar. The maximum adsorption capacity of tetracycline (TC) on MTWBC reached 293.46 mg·g-1, which was 15-fold more than that of TWBC (19.68 mg·g-1). An alkaline environment decreased the TC adsorption on biochars. The presence of Na+, K+, Ca2+, and Mg2+ inhibited TC adsorption onto biochars. The influence of Cu2+ on TC adsorption by biochars depends on its initial concentration. The enhanced adsorption capacity of TC on MTWBC was mainly attributable to the large surface area, the improved pore volume, and more aromatic structure. The adsorption mechanism was based on pore filling and π-π EDA interaction. Therefore, KHCO3 activated biochar has the potential to remove TC from aquatic environments.

Performance of CO2 and Fe-modified lignin char on arsenic (V) removal from water

Biochar was produced by the pyrolysis of Kraft lignin at 600 °C followed by modification with CO2 at 700 and 800 °C and impregnation with FeOx. The physicochemical properties and arsenic (V) adsorption performance of biochar were evaluated. The characteristics of the lignin biochar before and after CO2 modification and FeOx impregnation were analyzed using the following methods: proximate and ultimate analysis, specific surface area (Brunauer–Emmett–Teller (BET) surface area), porosity, scanning electron microscopy and energy dispersive spectroscopy mapping, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The specific surface area and porosity of biochar were improved significantly after CO2 modification. However, impregnation of FeOx in CO2-modified biochar showed a 50%–60% decrease of BET surface area and porosity due to pore blocking of FeOx. The batch adsorption of arsenic (V) showed that FeOx-LC-800 (FeOx impregnation lignin char modified with CO2 at 800 °C) had the highest adsorption efficiency among the biochars tested because of its highest Fe–O intensity and large surface area. The Langmuir adsorption model was suitable for the curve fitting arsenic (V) adsorption. The theoretical equilibrium adsorption amount (qe) was calculated to be 6.8 mg/g using a pseudo-second-order kinetic model.

Porous Biochars Derived from Microalgae Pyrolysis for CO2 Adsorption

In order to slow down the greenhouse warming caused by excessive CO₂ emissions and effectively exploit the byproducts produced during the biofuel production process, N-doped porous biochars derived from the byproducts of microalgae (chlorella and spirulina) pyrolysis by combining urea and KOH modification were synthesized in this article to remove CO₂ in simulated flue gas. The physicochemical properties of the microalgae porous biochars were investigated via characterization tools, involving pH, Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). CO₂ adsorption kinetics, thermodynamics, and CO₂ adsorption performance were also studied. Results reveal that the functional groups and specific surface areas of microalgae biochars are substantially increased via urea and KOH modification, and nitrogen-containing functional groups (mainly involving N–H, C–N, etc.) are major adsorption sites for CO₂ adsorption. The key control step for CO₂ adsorption is external mass transfer, and the CO₂ adsorption process over the microalgae porous biochars is mainly physical adsorption. Moreover, the chlorella-based porous biochars CNK-2 and spirulina-based porous biochars SNK-2 have optimal CO₂ removal performances, and their maximum adsorption capacities, respectively, reach 3.44 and 3.09 mmol/g at 25 °C. The results of regeneration studies demonstrate that, after 10 regeneration experiments, CNK-2 and SNK-2 still possess high CO₂ sorption performances (reaching 3.09 and 2.78 mmol/g, respectively), exhibiting good regeneration potential.

Physiochemical characterization of agricultural waste biochars for partial cement replacement

PurposeThe purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes.Design/methodology/approachBiochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests.FindingsAccelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement.Research limitations/implicationsWhile biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future.Practical implicationsCarbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs.Social implicationsReductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities.Originality/valueEmpirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.

Waste Plastics Complement Biochar: Innovative Approach in Curbing Toxicants (KCN/NaCN) in N-Containing Biochar

Alkaline metal cyanide (MCN) such as KCN or NaCN in N-containing biochar is a new obstacle for sustainable use of biochar. However, plastic waste can be utilized for solving these highly toxic substances MCN. In this work, plastic performed outstandingly in MCN elimination by preventing its parent formation (MOCN, e.g., KOCN) via complexation of alkaline metals and N. The CN– content in biochar was completely inhibited by co-pyrolysis with specific plastics from ∼30 000 to ∼0 mg/kg. Polyvinyl chloride, polytetrafluoroethylene, and triphenyl phosphate, which contain heteroatoms such as Cl, F, and P, can seize K atoms from biomass, resulting in the production of KCl, KF, K3PO4, and KPO3 instead of the KOCN (precursor of KCN). Furthermore, owing to the lack of ligand metal, N tended to dope into the biochar skeleton. Both reactions affected by plastic significantly led to the failure of MCN formation. After MCN controlled, an increase in N content and aromaticity and a decrease in the surface area of biochar were simultaneously observed. Unquestionably, biochar has become more environmentally friendly after MCN inhibition by plastic, as confirmed by the bio-assessment of the resultant biochar.

Biochar with large specific surface area recruits N2O-reducing microbes and mitigate N2O emission

Bacteria and archaea colonizing on biochar have been reported to possess nitrogen-metabolizing abilities. A larger specific surface area of biochar may enhance the activities of nitrous oxide (N2O)-reducing microbes, thereby mitigating N2O emission; however, the underlying mechanisms remain unclear. A 56-day incubation assay was performed with five treatments: no addition, urea only, and addition of three types of biochars (with different specific surface areas: 1193, 2023, and 2773 m2 g−1) combined with urea. N2O emission increased with the specific surface area of biochar up to 2023 m2 g−1 and decreased thereafter by 37% as compared with the urea only addition. By increasing soil pH, C/N ratio, nitrogen availability, and cation exchange capacity, the biochar with the largest specific surface area decreased soil N2O emission by affecting the diversity, abundance, and composition of total bacteria and N2O-producing microbial communities. A larger specific surface area of biochar correlated with a higher abundance of nitrogen-fixing (nifH), -nitrifying (amoA), and -denitrifying (nirK, nirS, and nosZ) genes. An increased abundance of ammonia-oxidizing bacteria and archaea, in the biochar with a smaller specific surface area, resulted in higher N2O emission. As the abundance of nosZ increased, the addition of the biochar with the largest specific surface area resulted in a higher ratio of nosZ/(amoA + nirS + nirK), leading to decreased N2O emission. Furthermore, the abundance of nifH, amoA, nirK, and nosZ on biochar (extraction from soil after 56-day incubation) was positively correlated with that in soil. Thus, the relative specific surface area of biochar should be taken into consideration when using it in agriculture, as our results show that biochars with larger specific surface areas decrease N2O emission by recruiting N2O-reducing microbes and upregulating the abundance of nitrogen-fixing, -nitrifying, and -denitrifying genes.