Physicochemical Properties Of Biochar Research Articles

Effects of pyrolysis parameters on physicochemical properties of biochar and bio-oil and application in asphalt.

Adoption of renewable energy sources such as biomass has been increasing worldwide. In this study, fast pyrolysis as an acceptable and viable method to get renewable bio-oil and biochar is used. Different temperatures and N2 flow velocities were used in the fast pyrolysis process to evaluate the pyrolysis yield of biochar and bio-oil. The waste wood and pig manure were utilized to prepare biochar and bio-oil. X-ray fluorescence, X-ray diffraction, high-pressure liquid chromatograph, Micro confocal laser Raman spectrometer, Fourier transform infrared spectrometer, and dynamic shear rheometer were used to measure the chemical compositions, structure, and pyrolysis yield of biochar and bio-oil. The obtained results indicate that pyrolysis temperature increases the purity of inorganic oxide in biochar and N2 flow velocity promotes the yield of carbon in biochar. The increase of N2 flow velocity would increase the acid property of bio-oil and damage the products yield of bio-oil. It was also observed that biochar could remarkably alter the fundamental performances of petroleum asphalt including penetration, softening point, ductility, viscosity, and complex modulus. The most important is that the upgraded bio-oil can be used to replace partly or fully the petroleum asphalt which is a promising biomass application.

Green conversion of bamboo chips into high-performance phenol adsorbent and supercapacitor electrodes by simultaneous activation and nitrogen doping

Nitrogen doping is one of the most promising approaches for improving the properties of carbon materials. Here, we reported a simple and effective method for the preparation of nanoporous nitrogen-doped carbonaceous material for liquid phase adsorbents and supercapacitor electrodes. In this method, the target carbonaceous material (biochar) was produced by one-step pyrolysis and activation of bamboo chips under the ammonia atmosphere. Two green activation reagents (K2C2O4 and KHCO3) were introduced into the preparation process simultaneously. The physicochemical properties of biochar were studied by means of SEM, BET, XRD, XPS and so on. The characterization results confirmed that the vascular bundle structure of bamboo can be well preserved by pyrolysis under ammonia atmosphere combined with green activation, and the nitrogen atoms were successfully introduced into the biochar’s skeleton uniformly. The physicochemical properties of biochar can be adjusted suitable for high phenol adsorption and supercapacitor electrodes at different temperatures. Optimum nitrogen-doped biochar showed a high phenol adsorption capacity of 169.5 mg/g at 25 ℃ and exhibited exceptional specific capacitance of 208 F/g at the current density of 1 A/g due to its unique nanoporous structures and surface functional groups. This novel nanoporous nitrogen-doped bamboo chips have great application potential in pollutant removal and energy storage.

Correlation between Physicochemical Properties of Biochar and Improved Interspecies Electron Transfer in Anaerobic Digestion of Whiskey By-Products

Stimulating interspecies electron transfer (IET) by biochars has been demonstrated as an efficient means to enhance anaerobic digestion (AD). However, the enhancing effects vary significantly depending on biochar properties. The correlations between them are not fully understood. Herein, biochars with different physicochemical properties were produced from a whiskey by-product “draff” and applied in the digestion of draff. The biochar produced at 700 °C enhanced biomethane yield by 5%, whereas biochars produced at 500 and 900 °C did not increase biomethane yield. The addition of 700 °C-derived biochar in AD increased the relative abundance of methanogen Methanosarcina, which may be the electron-accepting partner in direct interspecies electron transfer. The characterisation of biochar properties suggested that moderate graphitisation and abundant active surface functional groups (such as –C=O, pyridinic-N, and graphitic-N) contribute to a more stimulating IET through both the carbon matrices and the charging – discharging cycles of surface functional groups.

Priming, stabilization and temperature sensitivity of native SOC is controlled by microbial responses and physicochemical properties of biochar

Biochars generally result in short-term positive priming of native soil organic carbon (SOC), but longer-term carbon (C) stabilization, and these effects can be altered by global warming. However, uncertainty remains about the mechanisms associated with these priming effects, temperature sensitivity of native SOC, and microbial responses to biochars of differing properties. To address these knowledge gaps, rice straw biochars (produced at 300 and 800 °C at 2% w/w application rate), and their labile (water extracted) fraction and recalcitrant (chemically oxidized) fraction (obtained from the equivalent weight of biochar) were incubated in a C4 dominated soil at 15, 25, and 35 °C. Our results showed that 300 °C biochar and its recalcitrant fraction resulted in an increased SOC mineralization due to positive priming across the incubation thermosequence. This was likely linked to an observed increase in the abundance of K-strategists (fungi and Actinobacteria). The biochar produced at 800 °C and its recalcitrant fraction resulted in the stabilization of native SOC (i.e., negative priming) at all temperatures, likely due to the adsorptive protection of native SOC by the large surface area. The water extractable C from both biochars generally induced SOC stabilization across the thermosequence, which could be attributed to microbial shifts to r-strategists preferentially utilizing labile C components in biochar. Both biochars increased SOC stabilization with warming from 15 to 25 °C, supporting the role of biochar application in soil C sequestration in cooler regions. The lower SOC stabilization by biochars with temperature increases from 25 to 35 °C was correlated with the biochar-induced increases in fungal growth (K-strategist) under warming. The low-temperature biochar increased the abundance of aromatic C decomposers and concomitantly lowered the Q10 and activation energy (Ea) of native SOC. The findings from this study highlight that the low- and high-temperature biochars can result in various changes in native SOC mineralization, as well as temperature sensitivity, mainly by microbial population alterations and physicochemical interactions.

The removal of Pb2+ ion by MnFe2O4/waste tea leaves biochar and mechanism of adsorption

In order to transform waste tea leaves into a useful/valuable material for removal of Pb2+ ions from wastewater, MnFe2O4/biochar was synthesized. The tea waste was pyrolyzed at 500 °C to obtain the biochar. Effects of the composition of tea leaves on the physicochemical properties of biochar were evaluated. Biochar and MnFe2O4/biochar were mainly organic matter. Regarding inorganic components, aside from Fe and Mn there were considerable albeit small amounts of the mineral elements K and Ca in the MnFe2O4/biochar. The MnFe2O4/biochar is porous with a specific surface area of 24.38 m2 g−1, and the surface is loaded with MnFe2O4 and amorphous MnO2 particles. Also carboxylic acid, hydroxyl, and carbonyl functional groups were formed on the MnFe2O4/biochar surfaces. The surface area and pore volume characteristics of the MnFe2O4/biochar were also increased compared with the baseline biochar, and the prepared MnFe2O4/biochar had mesostructure. The modification of biochar into MnFe2O4/biochar improved adsorption of Pb2+ ions with the removal increased to ∼98%. The Freundlich isotherm and the pseudo-second order kinetic models matched well Pb2+ adsorption onto the MnFe2O4/biochar.

Copper(II) removal from aqua solution using rice straw derived biochar

Biochar derived from rice straw has potential application as a cheap adsorbent for removal of Cu(II) from aqueous solution. In this study, rice straw was used to derive biochar by operating at different pyrolysis temperatures (300, 400, and 500 °C) and studied different biochar physicochemical properties. Biochar yield decrease from 57.87 to 37.19% by increasing temperature from 300 to 500 °C. The content of carbon and ash, pH, and surface area of biochar increased from 68.72 to 81.48%, 32.70–46.52%, 8.23–11.4, 48.3–101.29, respectively. Batch adsorption was adopted for biochar produced at different temperatures, and biochar derived at 500 °C showed the greater adsorption capacity (29.8 mg g−1). RBC500 was selected to study the initial metal concentration effects (5–320 mg L−1) and time of contact (30–240 min) on removal efficiency of Cu(II). The optimum results from the study showed that for Cu adsorption was pH = 5, adsorbent dose 0.1 g L−1, and contact duration of 180 min. A strong fit to the kinetics (R2 = 0.99) was shown by pseudo-second-order model, and strong fit to the adsorption isotherms was shown by Langmuir model (R2 = 0.99) of Cu(II) adsorption.

EVALUATION OF PHOSPHATE AND AMMONIUM ADSORPTIONDESORPTION OF SLOW PYROLYZED WOOD BIOCHAR

Biochar is attracting attention as a soil amendment and organic/inorganic adsorbent for water purification. Proper use of biochar in such cases requires understanding of the mechanisms of nutrient adsorption and desorption on biochar. In this study, slow pyrolyzed wood biochar s were prepared at temperatures 400 and 600 C with retention time of 60 and 120 minutes to investigate their phosphate and ammonium adsorption capacities. The effects of pyrolysis process conditions and biochar physicochemical properties on potential adsorption capacity were evaluated. Results of adsorption kinetics showed that both pseudo-first-order and pseudosecond-order models could well predict the adsorption kinetics of phosphate and ammonium indicating that the chemical adsorption was one of the main mechanisms of phosphate and ammonium absorption. Langmuir-Freundlich isotherm was the best-fit model for ammonium adsorption which means the occurrence of chemical adsorption on heterogeneous surface whilst Langmuir isotherm agreed well with the phosphate adsorption. For different biochar s, ammonium adsorption capacity ranged from about 0.34 to 5.3 mg/g and phosphate adsorption capacity ranged from about 0.6 to 42.2 mg/g. Phosphate adsorption capacity improved with increasing temperature and retention time of pyrolysis process. However, higher ammonium adsorption which was observed in lower pyrolysis temperature and residence time can be attributed to more oxygen-containing functional groups. Both phosphate and ammonium adsorptions-desorption by biochar are more strongly related to solution pH, and maximum adsorption capacities were observed at pH of 7 and 3 for ammonium and phosphate, respectively.

Adsorption-enrichment characterization of CO2 and dynamic retention of free NH3 in functionalized biochar with H2O/NH3·H2O activation for promotion of new ammonia-based carbon capture

CO2 emission reduction has become a global consensus, and the most potential carbon emission reduction technology-Carbon Capture and Storage (CCS) is still in the development stage. In order to make up for the shortcomings of CCS technology, the idea of functionalized biochar-ammonia carbon capture system is proposed. Corn straw was used as raw materials, and activated biochar were prepared by one-step/two-step H2O/NH3·H2O activation, to construct a hierarchical-functionalized structure of biochar, and explore its adsorption characteristics of CO2 and NH3. Various methods such as solid characterization, temperature programmed desorption, molecular dynamics and quantum chemical simulation were used to explore the structure-effect relationship between the physicochemical properties of biochar and the adsorption of CO2 and NH3. The results show that the pore structure of gas-physical activated biochar is dominated by micropores. The one-step method is beneficial to the construction of functional groups on biochar surface, while the two-step one is conducive to the improvement of pore formation and its aromatization. During NH3·H2O activation, NH3 would inhibit the formation of O-containing functional groups on the surface of biochar by H2O. Compared with O-containing groups, the N-containing functional groups on biochar surface have greater adsorption energy for CO2 and NH3 adsorption. The adsorption sites of CO2 and NH3 are mainly in the micropores (d < 0.7 nm), and the contribution of functional groups in the micropores to the adsorption of CO2 and NH3 is greater than the pore structure. This study provided theoretical basis for the development of new biochar-ammonia CO2 capture system.

The impact of pyrolysis conditions on orange peel biochar physicochemical properties for sandy soil.

The citrus industry is considered one of the main contributors to agricultural waste. Peels are commonly used in the food industry or as feedstock in biorefining. In this study, the potential of waste orange peel biochar for agricultural applications in sandy soil was investigated. This will not only increase the percentage of agricultural waste recycling, but also lead to more sustainable agriculture with environmental benefits such as carbon sequestration. Biochar was produced through slow pyrolysis in the temperature range 300-600°C and at two holding durations (10 min and 60 min). Both factors had a significant impact on the physicochemical characteristics of biochar in the heating region 300-450°C. However, varying the holding time for pyrolysis temperatures beyond 450°C had a diminishing effect on biochar properties compared with the impact of increasing pyrolysis temperature. The study also looked at certain properties that are specific to agricultural application not previously reported for orange peel. Very high cation exchange capacities of 70 cmol kg-1 were achieved at 300°C, whereas water holding capacity was not strongly influenced by pyrolysis conditions. Preliminary planting tests indicate potential for improving agricultural sustainability in sandy soils. The technoeconomic analysis of biochar showed that the pyrolysis process can be profitable with sufficient plant capacity.

Poplar wood and tea biochars for trichloroethylene remediation in pure water and contaminated groundwater

Four biochars from pyrolysis of poplar wood (biochar P) and tea (biochar T) at 450 and 750 °C have been tested in a first time as adsorbents for trichloroethylene (TCE) removal in groundwater. The physico-chemical properties of biochars were systematically investigated with organic elemental analyser, scanning electron microscopy, N2 adsorption measurement, IR spectroscopy and X-ray photoelectron microscopy. Three kinetic models were used to follow the TCE removal by biochars. The best kinetic performances were obtained with biochars P with the smallest particle size diameter (50 – 100 µm) due to their porosity and the mass transfer limitation for the TCE remediation. Remediation of a real sample of groundwater polluted by chlorinated organic compounds showed that biochar P produced at 750 °C is more efficient to remove vinyl chloride (65% adsorbed) than commercial activated carbon powder (40%). The TCE sorption capacity is similar in pure water and in polluted groundwater. The results also highlighted better retention capacity for the most substituted molecules (tri and tetrachloroethylene) for biochar P750.

Production and Characterization of Biochars from Slow Pyrolysis of Different Biomass Materials to Evaluate Properties as Soil Amendments

Biochar, a carbon (C)-rich solid material produced by the thermo-chemical conversion of biomass in an oxygen-limited environment, has been attracting interest due to its potential as a soil amendment. In this study, biomass materials derived from rice (Oryza sativa) straw (RS), rice hull (RH), water hyacinth (Eichhornia crassipes) (WH), and mahogany flower receptacles (Swietenia macrophylla) (MFR) were slowly pyrolyzed under temperatures ranging from 300–650°C using a biochar producing stove. The morphological characteristics and physicochemical properties of biochars were studied using the Brunauer-Emmett-Teller (BET) automated nitrogen multilayer physisorption system, field emission–transmission electron microscopy (FE-TEM), and X-ray energy dispersive spectrometry (EDS). Biochars originating from light materials (RS and WH) showed higher concentrations of essential plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K). The biochar originating from woody MFR had low concentrations of essential plant nutrients. The surface area of the materials was in the 0.473–78.208 m2/g range. The RS and RH biochars demonstrated high surface area with 45.511 and 78.208 m2/g, respectively. The WH biochar showed a low surface area of 9.845 m2/g while the surface area of the MFR biochar was particularly very low at 0.473 m2/g. The high angle annular bright-field (HAABF) images, spectra, and elemental X-ray maps of all the four biochars revealed areas high in carbon, potassium, chlorine, calcium, magnesium, silicon, and aluminum. These biochar properties and mineral agglomerates suggest that biochars can be used as a soil amendment to improve soil fertility.

Effects of pyrolysis temperature on production and physicochemical characterization of biochar derived from coconut fiber biomass through slow pyrolysis process

The purposes of this research were to investigate the competence of coconut fiber to produce biochar by slow pyrolysis process and analyze the effects of different pyrolysis temperatures on the yield and physicochemical properties of biochars. Coconut fiber biomass was subjected to slow pyrolysis process using a laboratory scale fixed bed reactor at six different temperatures ranging from 350 to 600 °C (at an interval of 50 °C). The slow pyrolysis process was carried out in an inert environment for 1 (one) hour at a constant heating rate of 10 °C/min. The physicochemical properties of biomass and obtained biochars were characterized by proximate analysis (VM, FC, ash), ultimate analysis (CHNSO), higher heating value (HHV), bulk density, BET surface area, pH, and electrical conductivity (EC). Functional groups and particle sizes of biomass and biochars were identified by FTIR and particle size distribution respectively. Surface morphology and pore distribution of the biochars were observed by SEM images. The pyrolysis temperature had a negative effect on biochar yield and reduced from 48.13 to 29.34% as the pyrolysis temperature increased from 350 to 600 °C. Fixed carbon, ash content, pH, organic carbon, specific surface area, EC, degree of aromaticity, and porosity of the biochars enhanced as the pyrolysis temperature rose from 350 to 600 °C. However, the volatile matter, VM/FC ratio, H/C ratio, HHV, bulk density, and particle sizes of biochars were negatively correlated with the pyrolysis temperatures. Higher pyrolysis temperatures increased aromatic C groups and recalcitrant characteristics, yielded smaller particles, and formed elongated and porous structures. The physicochemical properties of high-temperature biochars (500–600 °C) showed the potential to be used as soil amendments and an efficient tool for C sequestration and retention of nutrients, and water. The porous structures of high-temperature biochars can accommodate suitable soil-microorganism activities, increase water sorption, and increase soil density. Moreover, the high alkalinity of the biochars can assist to neutralize acidic soil and increases soil fertility and plant growth. On the contrary, low-temperature biochars (350–450 °C) are promising tools for solid fuels.

Combined biochar and soda residues increases maize yields and decreases grain Cd/Pb in a highly Cd/Pb-polluted acid Udults soil

Excessive heavy metal (HM) in soil limit crop yields and reduce quality of crops and soil. In this study, a 3-year field experiment was conducted to verify the effects of different amendment treatments on the accumulation and distribution of cadmium/lead (Cd/Pb) on maize aboveground parts and the availability of Cd/Pb in Udults soil. The treatments were CK, biochar at 5, 10, 20, 30 t ha−1 (B1–B4), soda residues at 3 t ha−1 (M) and biochar & soda residues (10 t ha−1 + 3 t ha−1; B2M). The results show that the greater the applied biochar dose, the longer lasting the mediating effect; however, the B2M treatment was the most effective and had the longest-lasting effects. Compared to CK, the B2M treatment significantly increased soil pH and total organic carbon levels by 0.68–1.44 pH units and 16.2 %–30.3 %, respectively, and reduced available Cd/Pb by 52.4 %–68.6 % and 28.3 %–40.8 %, respectively. Additionally, B2M also increased the maize grain yield by 7985.2–10,728.9 kg ha−1 and decreased the Cd/Pb contents of maize grains by 0.16–0.21 mg kg−1 (Cd) and 0.05–0.51 mg kg−1 (Pb) over the 3-year period. The Cd/Pb contents in maize grain were lower than the feed additive standard (GB 13078−2017), indicating that this product can be used as animal feed. Soil pH was the most important factor to control Cd/Pb accumulation, while the Cd was also influenced by biochar physicochemical properties such as specific surface area, aromatic structures and oxygen-containing functional groups. A cost analysis for this field experiment revealed that applying combined biochar and soda residues to polluted soil had an economic benefit whereas the application of biochar alone did not.

The addition of biochar as a fertilizer supplement for the attenuation of potentially toxic elements in phosphogypsum-amended soil

Phosphogypsum (PG) is an acid by-product generated during the breakdown of phosphate ore in the presence of sulfuric acid and has been used as a soil amendment, i.e., fertilizer , in most parts of the world. PG application can improve some soil properties and increase crop yields. However, PG application in agriculture threatens agroecological systems and food safety because of the high amounts of environmentally and biologically available potentially toxic elements (PTEs) in PG. Recently, biochar has been found to strongly immobilize and adsorb PTEs as well as suppress PTE phytoavailability. Hence, in this context, bench-scale batch and column experiments were performed to test the availability of PTEs in PG under different pyrolysis temperatures and different percentages of rice husk biochar (RHB). Subsequently, pot experiments were performed to test the effect of RHB addition on the PTE concentrations in crops when PG was added to different types of soil, and the effect of the RHB and PG combination on crop yield was determined. The batch and column experimental results showed that the pyrolysis temperature and biochar dose significantly reduced the PTE concentrations in PG because the biochar physicochemical properties , components, and types of functional groups, which were analysed by XRF , XRD and FTIR, were mainly controlled by temperature. The preparation temperature (600 °C) and applied dose (60%, w/w) of RHB were optimized through a mixed-effect model. Furthermore, the mechanism underlying P, F and heavy metals in PG leachates adsorbed onto biochar was determined by XPS analysis, which showed that surface ions and different functional groups played a dominant role through precipitation and complexation. Compared to the control, application of the combination to loam soil or sand significantly increased (56.04% and 604.66%, respectively) crop yield. The combination significantly decreased PTE concentrations (As, F, Cd, and Pb by 39, 41, 75, and 86%, respectively, in water spinach and by 100%, 64%, 75%, and 88%, respectively, in asparagus lettuce) in edible parts of crops compared to PG treatment only. Moreover, RHB + PG reduced pollution to the surrounding environment by decreasing the PTE contents in the leachate. These findings suggest that the improved effectiveness of the combination was greater in sand because of its weak buffering ability, and the RHB and PG combination can be a useful and safe soil amendment to provide good guidance for waste management and comprehensive utilization of waste. • Added rice husk biochar (RHB) reduced pollutant levels in phosphogypsum (PG). • Dosage and pyrolysis temperature were main controlling factors for PG treatment. • RHB and PG addition greatly increased veggies yield and nutrient concentrations. • RHB decreased pollutant contents in edible parts when used with PG as modifier. • Combination of PG and RHB achieved waste management and sustainability.

Sediment-based biochar facilitates highly efficient nitrate removal: Physicochemical properties, biological responses and potential mechanism

Biological removal of the nitrate, a highly concerning contaminant in rivers, is limited due to the low activity of denitrifying community. Biochar is extensively used in facilitating the nitrate removal because of its unique physicochemical properties which enhance the denitrifying performance in aqueous environment. However, the physicochemical properties of biochar and its potential strengthening mechanism in denitrification process remains unknown. Herein, the sediment-based biochar was prepared for strengthening denitrification for the first time. The biochar was prepared at 400–1100 °C, with its conductivity increasing from 0.21 to 310.11 S m−1 while nitrogen (oxygen) content decreasing from 5.81% (20.30%) to 3.79% (16.63%). A maximum total nitrogen (TN) removal rate of 21.67 ± 0.66 g N m−3 d-1 with a nitrate nitrogen (NO3−-N) removal rate of 22.43 ± 0.62 g N m−3 d-1 was obtained when biochar at pyrolysis temperature of 800 °C (SBC800) was added, which were 11.6- and 5.0-fold higher than that without biochar, indicating an ameliorative denitrification performance. The nitrogen-containing functional groups were correlated significantly with electron donating capacity (EDC, r = 0.898, p < 0.05) and electron accepting capacity (EAC, r = 0.911, p < 0.05) of biochar, further increased the abundance of denitrifying species to 75.9% by gaining high correlation with NO3−-N removal (r = 0.903, p < 0.05). Overall, this study provides a low-cost and sustainable way to efficiently remove nitrogen from fluvial systems using sediment-based biochar.

Opportunity for sustainable biomass valorization to produce biochar for improving soil characteristics

Biochar, a byproduct obtained from valorization of waste biomass, is utilized in environmental management to restore or improve soil functions where it alters chemical, physical, and biological processes. Therefore, in this study, vastly available oak sawdust was evaluated as a potential feedstock for biochar production with the aim to identify the influence of carbonization conditions on biochar characteristics. Slow pyrolysis with temperatures ranging from 400 to 600 °C and residence times from 15 to 120 min was performed. The feedstock material and resulting biochar were characterized for physical, chemical, and hydraulic properties that are significant for their ability and characteristics as a soil amendment. The pH, BET surface area, carbon content, nutrient content, alkaline functional groups, and water holding capacity increased with increasing pyrolysis temperature and residence time while biochar yield, O/C ratio, and acidic functional groups decreased. Although the effect of holding time on biochar physicochemical properties is less significant than that of temperature, it is an essential parameter to obtain desired biochar properties. It can be concluded that pyrolysis has the potential to add value to regionally available oak sawdust on a sustainable basis and help to restore or improve essential soil functions.Graphical abstract

Biomass-derived activated carbons for the removal of pharmaceutical mircopollutants from wastewater: A review

Biomass-derived activated carbons (biochars) have attracted great attention due to their excellent physicochemical properties such as high specific area, large pore volume, well-defined microporous structure and tunable surface chemistry. Although pharmaceuticals are an emerging class of micropollutants in wastewater through the sewerage disposal by pharmaceutical factories, hospitals and households, only a few recent studies have reviewed the adsorption and removal of pharmaceuticals from wastewater by biochars and they lack the systematic insights into total adsorption process from biochars preparation to adsorption mechanism. This paper aims to provide a comprehensive review on recent publications and to propose future research directions. The effects of lignocellulosic biomass as well as the pyrolysis, activation and modification conditions on the physicochemical properties of biochars and their adsorption capacities are discussed. The adsorption kinetics and isotherms of different pharmaceuticals onto various biochars are analyzed based on commonly used models. Finally, the potential adsorption mechanisms of pharmaceuticals by biochars are summarized.

Effect of Pyrolysis Temperature on PhysicoChemical Properties and Acoustic-Based Amination of Biochar for Efficient CO2 Adsorption

The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) or agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures- 500, 600, 700 and 800 oC. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. As per the elemental analysis, the elevated pyrolysis temperature resulted in increased %C and %ash contents and reduced %N contents of biochar. The textural analysis exhibited almost 3-times enhancement of micro surface area and pore volume upon increasing the pyrolysis temperature from 500 to 700 oC, though further increase to 800 oC reduced the micro-porosity and the surface area. The intermediate temperatures of 600 and 700 oC revealed the highest interactions with ultrasound-amination, which significantly intensified CO2 adsorption. Accordingly, the CO2 capture capacity of sono-aminated biochars synthesized at 600 and 700 oC were almost 200% greater than that of raw biochars. There were 127-159% and 115-151% increases in adsorption capacity of biochars synthesized at 800 and 500 oC upon ultrasono-amine functionalization. Miscanthus biochar synthesized at 700 oC and treated sono-chemically demonstrated the highest adsorption ability of 2.89 mmol/g at 70 oC and 0.10 atm partial pressure, which is 211% higher than its pristine condition. The superior adsorption capacity of miscanthus (at 700 oC) can be attributed to its large surface area (324.35 m2/g), high carbon content (84%), and low ash content (4.9%), as well as its %N content after sono-amination that was twice that of raw char.

A critical review on arsenic removal from water using biochar-based sorbents: The significance of modification and redox reactions

Biochar is considered to be the cost-effective, environmentally-friendly and sustainable sorbent that has an extraordinary potential to efficiently remove toxic elements, including arsenic (As) from water. Until now, no review has focused to understand various important and intriguing aspects on biochar use as a sorbent for As removal from water, either pristine or modified. This review discusses various factors governing As removal potential of biochars (e.g., pH, biochar dose and physico-chemical properties of biochar), sequestration mechanisms, fate of sorbed As on biochar and the redox-mediated interactions between biochar and As. The significance of biochar-derived materials for the treatment of As-contaminated drinking water/wastewater and their potential regeneration ability is also critically discussed, which has not been previously elaborated. This comprehensive review article could be greatly valuable for scientists, policymakers, water treatment industries, environmentalists and graduate students, who are involved in biochar-As research. The review covers some new overarching and key scientific opportunities for the remediation of As-contaminated water using biochar-based materials, which is a potential health risk to millions of people worldwide.

Co-gasification of digestate and lignite in a downdraft fixed bed gasifier: Effect of temperature

To improve energy efficiency and biomass utilization in the process of anaerobic digestion, co-gasification is considered as an effective method to post-treat anaerobic digestion residues. In this work, the effect of temperature (650 °C, 750 °C, 850 °C and 950 °C) on the co-gasification of digestate and lignite was thoroughly investigated in a downdraft fixed bed gasifier. The results showed that the increase of gasification temperature increased the gas yield and the lower heating value (LHV) of product gas. Physicochemical properties of biochar were characterized by physical adsorption analyzer, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and thermogravimetric analyzer (TG). It was shown that the average pore diameter increased in the range of 650 °C to 950 °C, while specific surface area and pore volume first increased from 650 °C to 850 °C and then decreased at 950 °C. The Raman analysis of biochar indicated that small aromatic rings condensed to large aromatic ring and increased the content of Caromatic-Calkyl and the crosslinking density at higher temperature. The variation of biochar properties at the higher temperature caused a decrease in the gasification reactivity. With the increase of temperature, the content of carbolic oil in the tar increased, but the contents of light oil, naphthalene oil and washing oil decreased. This study comprehensively analyzed the products properties and demonstrated the feasibility of co-gasification of digestate and lignite.