Varying Pyrolysis Temperature Research Articles

Biochar-bacteria coupling system enhanced the bioremediation of phenol wastewater-based on life cycle assessment and environmental safety analysis

The efficient treatment of phenol wastewater is of great necessity since it induces serious pollution of water and soil ecosystems. Using biochar-immobilized functional microorganisms can innovatively and sustainably deal with the existing problem. In this study, we utilized response surface methodology (RSM) combined with life cycle assessment (LCA) to improve phenol biodegradation rate through a novel separated alkali-resistant and thermophilic strain Bacillus halotolerans ACY. Bioinformatic analysis revealed the genetic foundation of ACY to adapt to harsh environments. The characteristics of pig manure biochar (PMB) produced at varying pyrolysis temperatures (300–700 ℃) and adsorption experiment were investigated, immobilization of the phenol-degrading ACY on PMB600 under alkaline and high pollution load promoted phenol removal and extreme environment resistance, and the phenol removal rate reached 99.5 % in 7d in actual phenol wastewater, which increased compared with those achieved by PMB (50.6 %) and free bacteria (80.5 %) alone. Scanning Electron Microscope (SEM) and Fourier transform infrared spectrometry (FTIR) observations indicated the successful bacterial immobilization on PMB600. Reusability and economic cost study further demonstrated PMB600 as an excellent carrier for wastewater treatment. LC-MS, toxicology and carbon footprint analyses demonstrated that bacterial metabolism exerted synergy with adsorption for phenol removal, while biodegradation exerted the predominant impact on the immobilized bacterial system. This study provides an eco-friendly and effective approach to treat phenol wastewater.

The Influence of Pyrolysis Temperature and Feedstocks on the Characteristics of Biochar-Derived Dissolved Organic Matter: A Systematic Assessment

Biochar is a carbon-rich product obtained by pyrolyzing biomass under oxygen-limited conditions and has a wide range of potential for environmental applications. In particular, dissolved organic matter (DOM) released from biochar has an important impact on the fate of pollutants. The study aimed to systematically assess how varying pyrolysis temperatures and biomass feedstocks influence the characteristics of biochar-derived DOM. DOM samples were comprehensively characterized utilizing UV-vis spectroscopy and excitation–emission matrix (EEM) fluorescence spectroscopy, coupled with parallel factor (PARAFAC) analysis. The study discovered that pyrolysis temperature significantly affects DOM characteristics more than feedstock type. An increase in pyrolysis temperature correlated with a notable decrease in dissolved organic carbon content, aromaticity, and fluorescence intensity, alongside a marked increase in pH and hydrophilicity. PARAFAC analysis identified three distinct DOM components: two humic-like substances (C1 and C2) and one protein-like substance (C3). The proportion of protein-like substances increased with higher pyrolysis temperatures, while the humic-like substances’ proportion declined. The compositional shifts in DOM with pyrolysis temperature may significantly influence its environmental behavior and functionality. Further research is necessary to explore the long-term environmental impact and potential applications of biochar-derived DOM.

Adsorptive removal of diclofenac on nanoporous anoxic sewage sludge biochar: Investigating the influence of carbonization temperature, residence time and specific Fe(III) infusion

This study explores the removal of the emerging contaminant diclofenac using pristine biochar and iron-impregnated biochar derived from anoxic sewage sludge. A biochar ensemble was prepared at varying pyrolysis temperatures (350 °C to 950 °C) and residence times (30 to 240 min). The iron-modified material was synthesized by incorporating FeCl3 with the precursor at 950 °C for 30 min. A comprehensive characterization based on the morphology, crystallinity, and functional groups confirmed the structural and chemical modifications in the pristine and modified biochar of interest. Adsorption experiments demonstrated that iron-modified biochar exhibited superior adsorption capacity for diclofenac (18.958±0.417 mg/g) compared to pristine biochar (0.814±0.001 mg/g), attributable to its larger surface area and more active sites. The adsorption mechanisms were identified as a combination of electrostatic interactions, hydrogen bonding, and complexation, with significant Fe3+ to Fe2+ reduction indicating electron transfer processes. Adsorption kinetics followed the Elovich model, and equilibrium studies fitted best to the Redlich-Peterson model for the iron-amended biochar. The study also assessed the reusability of the adsorbents, with pristine and iron-impregnated biochar maintaining around 70 % removal efficiency up to 3 and 5 cycles, respectively. Consequently, both the biochar serve as potentially efficient adsorbents for diclofenac removal from aqueous solutions.

Study on the influence of Ni/La2O3/CeO2 composite catalysts on the characteristics and stability of biomass pyrolysis components

The impact of adding La2O3 and CeO2 separately or in combination to a Ni-Al2O3 catalyst on the volatile components of biomass pyrolysis is examined in this study. This study focuses on the effects of varying pyrolysis temperatures and catalyst usage cycles on catalytic reforming, evaluating the resulting pyrolysis yield, syngas composition, and catalyst stability. Catalyst characteristics are also analyzed. The results of this study show that the Ni-Al2O3 catalyst modified with La2O3 alone produces a 9 % reduction in tar yield and a 20 % increase in the CO + H2 fraction of the pyrolysis gas compared to the control group. When modified with CeO2 alone, the Ni-Al2O3 catalyst keeps a tar conversion efficiency above 43 % after ten consecutive usage cycles. The addition of La2O3 and CeO2 simultaneously led to a 19 % increase in hydrogen yield, with the absolute content of alcohols, ketones, and esters reaching zero at 850°C.

The impact of water hyacinth biochar on maize growth and soil properties: The influence of pyrolysis temperature

AbstractIntroductionOptions for managing water hyacinths (WHs) include converting the biomass into biochar for soil amendment. However, less has been known about the impact of WH‐based biochar developed in varying pyrolysis temperatures on plant growth and soil qualities.Materials and MethodsA pot experiment was undertaken in a factorial combination of WH biochars (WHBs) developed at three temperatures (350°C, 550°C and 750°C) and two application rates (5 and 20 t ha−1), plus a control without biochar. Maize was grown as a test crop for 2 months under natural conditions.ResultsOur study showed that applying WHB developed between 350°C and 750°C at 20 t ha−1 increased maize shoot and root dry biomass by 47.7% to 17.6% and 78.4% to 54.1%, respectively. Nevertheless, raising the biochar pyrolysis temperature decreased maize growth, whereas increasing the application rate displayed a positive effect. The application of WHB generated at 350°C and 550°C at 20 t ha−1 resulted in significant improvements in soil total nitrogen (17.9% to 25%), cation exchange capacity (27.3% to 20.2%), and ammonium‐nitrogen (60.7% to 59.6%), respectively, over the control. Additionally, applying WHB produced from 350°C to 750°C at 20 t ha−1 enhanced soil carbon by 38.5%–56.3%, compared to the control. Conversely, applying biochar produced at 750°C resulted in higher soil pH (6.3 ± 0.103), electrical conductivity (0.23 ± 0.01 dS m−1) and available phosphorus (21.8 ± 2.53 mg kg−1).ConclusionWHBs developed at temperatures of 350°C and 550°C with an application rate of 20 t ha−1 were found to be optimal for growing maize and improving soil characteristics. Our study concludes that pyrolysis temperature significantly governs the effectiveness of biochar produced from a specific biomass source.

Environmental remediation potential of a pioneer plant (Miscanthus sp.) from abandoned mine into biochar: Heavy metal stabilization and environmental application

Pyrolysis stands out as an effective method for the disposal of phytoremediation residues in abandoned mines, yielding a valuable by-product, biochar. However, the environmental application of biochar derived from such residues is limited by the potential environmental risks of heavy metals. Herein, Miscanthus sp. residues from abandoned mines were pyrolyzed into biochars at varied pyrolysis temperatures (300–700 °C) to facilitate the safe reuse of phytoremediation residues. The results showed that pyrolysis significantly stabilizes heavy metals in biomass, with Cd exhibiting the most notable stabilization effect. Acid-soluble/exchangeable and reducible fractions of Cd decreased significantly from 69.91 % to 2.52 %, and oxidizable and residue fractions increased approximately 3.24 times at 700 °C. The environmental risk assessment indicated that biochar pyrolyzed over 500 °C pose lower environmental risk (RI < 30), making them optimal for the safe utilization of phytoremediation residues. Additionally, adsorption experiments suggested that biochars prepared at higher temperature (500–700 °C) exhibit superior adsorption capacity, attributed to alkalinity and precipitation effect. This study highlights that biochars produced by pyrolyzing Miscanthus sp. from abandoned mines above 500 °C hold promise for environmental remediation, offering novel insight into the reutilization of metal-rich biomass.

Boosting acetaminophen degradation in water by peracetic acid activation: A novel approach using chestnut shell-derived biochar at varied pyrolysis temperatures

In this study, biochar derived from chestnut shells was synthesized through pyrolysis at varying temperatures from 300 °C to 900 °C. The study unveiled that the pyrolysis temperature is pivotal in defining the physical and chemical attributes of biochar, notably its adsorption capabilities and its role in activating peracetic acid (PAA) for the efficient removal of acetaminophen (APAP) from aquatic environments. Notably, the biochar processed at 900 °C, referred to as CN900, demonstrated an exceptional adsorption efficiency of 55.8 mg g−1, significantly outperforming its counterparts produced at lower temperatures (CN300, CN500, and CN700). This enhanced performance of CN900 is attributed to its increased surface area, improved micro-porosity, and a greater abundance of oxygen-containing functional groups, which are a consequence of the elevated pyrolysis temperature. These oxygen-rich functional groups, such as carbonyls, play a crucial role in facilitating the decomposition of the O–O bond in PAA, leading to the generation of reactive oxygen species (ROS) through electron transfer mechanisms. This investigation contributes to the development of sustainable and cost-effective materials for water purification, underscoring the potential of chestnut shell-derived biochar as an efficient adsorbent and catalyst for PAA activation, thereby offering a viable solution for environmental cleanup efforts.

Synergistic enhancement of bio-oil production, quality, and optimization from co-pyrolysis purun tikus (Eleocharis dulcis) and plastic waste using response surface methodology

This study investigated the influence of varying pyrolysis temperatures (400–600°C) and biomass-to-plastic waste ratios (100:0, 70:30, 60:40, 50:50, and 40:60) on the product distribution during the co-pyrolysis of Purun tikus (PT) and Polyethylene Terephthalate (PET). The investigation revealed positive synergistic interactions. Notably, the bio-oil yield experienced a significant enhancement under optimal operational conditions (feedstock ratio of 40PT:60PET and a pyrolysis temperature of 600°C), with the yield doubling that of the feedstock ratio of 100PT. The composition of bio-oil compounds was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS), revealing that the most abundant compounds were esters (ranging from 30.1 % to 37.2 % area), phenolics (ranging from 11.3 % to 32.2 % area), and furfural (ranging from 4.5 % to 18.5 % area). The study further explored the impact of different experimental conditions on the yields of bio-oil, bio-char, and syngas through the application of response surface methodology. It was determined that the optimal yield of bio-oil was attainable by adjusting the reaction temperature and the ratio of PT to PET. The identified optimum conditions, which resulted in the maximum bio-oil output of 40.46 %, were a PT to PET ratio of 40:60 and a temperature of 600°C.

The chemical composition of Savannah bamboo (Oxytenanthera abyssinica) vinegar at varying pyrolysis temperatures and its termiticidal activity against wood-feeding termites

Synthetic biocides used in wood preservation present significant environmental and human health risks. An environmentally responsible and efficient substitute for traditional pesticides is bamboo vinegar. However, the chemical component of vinegar, which varies depending on the bamboo species, affects how efficient it is as a preservative. This investigation identified the constituent chemicals and termiticidal properties of vinegar derived from Savannah bamboo (Oxytenanthera abyssinica (A.Rich.) Munro) prepared at various temperatures. Savannah bamboo was pyrolyzed at 350°C, 400°C, and 450°C following established procedures to extract vinegar. Gas Chromatography-Mass Spectrometry (GC-MS) was used to characterize the vinegar's ingredients. The British standard EN 252 was used to assess the vinegar's termiticidal efficacy. The greatest amount of vinegar (0.45 kg) was produced at 450 °C. The vinegar mostly comprised hexadecanoic, pentadecanoic, octadecanoic, and (3,3-dimethyl-1-phenylbut-1-enyl) benzene. The proportions of these primary constituents varied depending on the pyrolyzing temperature. With its highest content of fatty acids, the vinegar generated at 450°C had the strongest termiticidal activity. O. abyssinica vinegar could provide an eco-friendly substitute for artificial biocides. The manufacturing of vinegar from O. abyssinica could open up new markets for industries engaged in the production, processing, and product development of bamboo.

Effect of biochar addition on CO2 emission from salt-affected soils under drying-rewetting conditions

Under the conditions of global climate change, soils have undergone more complex and frequent cycles of wetting and drying, which has had a significant impact on soil respiration. In order to explore the response of CO2 emissions from salt-affected soils to biochar (BC) at different pyrolysis temperatures under drying-rewetting conditions, an indoor microcosmic culture experiment was conducted to add maize straw BC at different pyrolysis temperatures (300°C and 600°C) to salt-affected soils to study the influence of BC at different pyrolysis temperatures on the characteristics of CO2 emissions under drying-rewetting conditions. The results indicated that the addition of BC significantly altered the CO2 emission rate from the soil, subsequently influencing the mineralization of soil organic carbon. BC produced at varying pyrolysis temperatures exhibited distinct effects on the CO2 emission rates. Specifically, BC pyrolyzed at high temperatures inhibited the mineralization of soil organic carbon, whereas BC produced at low temperatures facilitated this mineralization process. This finding will provide a theoretical and scientific foundation for assessing the carbon sequestration potential of coastal wetlands and for the development of carbon sequestration technologies.

New insights into temperature-induced mechanisms of copper adsorption enhancement on hydroxyapatite-in situ self-doped fluffy bread-like biochar

The utilization of kitchen bones as a renewable resource for biochar production holds significant promise. In this study, three distinct pig-bone-based biochars (PBCs) were synthesized at varying pyrolysis temperatures to investigate the influences of Hydroxyapatite (HAP) self-doped on crystal morphology, formation of functional active sites, and Cu2+ efficient adsorption. The results showed that low-temperature-induced alterations in HAP crystal morphology led to the formation of a highly active “fluffy bread-like” structure (FBS) in PBC-500, exhibiting exceptional Cu2+ adsorption capacity (71.60 mg·L−1) with an 86% adsorption achieved within 15 min. Notably, PBC-500 demonstrated a unit-specific surface area adsorption capacity for Cu2+, which was 1.52 and 1.19 times higher than the nano-wire-like PBC-700 and the nano-spherical-like PBC-900, respectively. Modern Spectroscopic analyses established the presence of a range of active centers (–OH, –CONH2, -PO43-) on PBC-500′s FBS carrier along with its highly efficient adsorption mechanism for Cu2+. These findings were strongly supported by electrostatic potentials and the frontier orbital theory of Quantum DFT methods, providing insights into the crucial chemical mechanisms by which active sites, such as phosphorus, nitrogen, and oxygen centers, enhance Cu2+ adsorption. Furthermore, PBC-500 exhibited superior adsorption binding energy and chemical reactivity, retaining high activity across a range of pH levels, inorganic ions, and organic matter. This study establishes empirical and theoretical foundations for the efficient utilization of kitchen pig bones as a sustainable resource and the eco-friendly synthesis of high-performance self-doped biochar, contributing to sustainable material innovation.

N-doped coal-based carbon membrane coupling peroxymonosulfate activation for bisphenol A degradation: The role of micro-carbon structure and nitrogen species

Herein, a novel N-doped coal-based carbon membrane (N-CCM) was prepared by using melamine as N source with high-temperature pyrolysis assistance. Through reasonable regulation of membrane micro-carbon structure and N species by varying pyrolysis temperature, the N-CCM integrated with peroxymonosulfate (PMS) activation under membrane filtration (MFPA) process showed excellent bisphenol A (BPA) removal of 98.3%. The excellent performance of N-CCM MFPA process was mainly owing to the following reason: For one thing, the more orderly micro-carbon structure of N-CCM possessed high defect density and boundary active sites under suitable pyrolysis temperature (700 °C), contributing to PMS activation (enhanced generation of reactive oxygen species (ROS) and electron transfer). For another, pyrrolic N, pyridinic N and C=C were beneficial to PMS adsorption and facilitate the electrons transfer from BPA to PMS. While C–O and graphitic N were responsible for the generation of ROS (SO4•−, •OH and 1O2). Theoretical calculations showed that the bond length of O–O, O–H and O–S in PMS adsorbed on C atom near N sites was significantly lengthened, corresponding to the generated ROS. Overall, the co-effect of radical process (SO4•− and •OH) and non-radical process (1O2 and electron transfer) achieved efficient BPA degradation in system.

Investigations on carbonization operating conditions of ANSYS customized kiln for charcoal production from Prosopis juliflora biomass and ANN model prediction for optimized operating conditions

The majority of the population still uses charcoal for domestic and industrial purposes. Charcoal is favored by many developing countries because of its low cost and ever-increasing energy demand. The objective of this study is to provide the optimum temperature and moisture content for a fixed residence time toobtain a good quality charcoal yield. The kiln model has been validated using ANSYS, before fabricating the kiln. The selected kiln is a verticalrectangular steel kiln and horizontal square stacking is followed. The wood used for charcoal production is Prosopis juliflora. Initially, wood is subjected to a pyrolysis process to determine the optimum residence time, 3 and 4 hrs were considered for the experiment. The wood is subjected to a pyrolysis process for different moisture content of 30.7 and 15.45% in varying pyrolysis temperatures of 350, 380, 420, 450 and 500 ⁰C. from the experimental results, it is revealed that the optimum residing time is 4 hrs and the optimum temperature is 500 ⁰C, because more time facilitates the evaporation of lite volatile matter and forms a good quality of charcoal yield with more fixed carbon if 15.45 % moisture air dried wood is used. ANN model was developed and evaluated for a different training function by varying hidden layer neuron numbers. The suitability of the developed ANN model is verified based on deviation in error with the experimental values for different input values.

Synthesis of Carbon from Rice Groats at Various Pyrolysis Temperatures and Its Application for the Recovery of Chromium Wastewater from the Tannery Industry

The research on synthesis of carbon from rice groats at various pyrolysis temperatures and its application for the recovery of chromium wastewater from the tannery industry by varying pyrolysis temperatures at 300, 400, and 500 °C. The results of carbon synthesis are analyzed in the form of determination of yield, water content, ash content, and iodine number. The best pyrolysis condition with the quality requirement of carbon is at a pyrolysis temperature of 500 °C with 760 mg.g-1 (iodine number). Adsorption kinetics was also carried out to determine the adsorption kinetics of chromium ions from tannery wastewater. Adsorption kinetics model of chromium wastewater from the tannery industry corresponds to the pseudo-second-order kinetics model with R2 is 0.9857, k2 is 0.0093 g.mg-1.min-1, and qe is 28.5714 mg.g-1.

Optimizing date palm leaf and pistachio shell biochar properties for antibiotic adsorption by varying pyrolysis temperature

This study implemented biochars produced from two arid agricultural byproducts, date palm leaves and pistachio shells, at pyrolysis temperatures from 400 to 800 °C to remove trimethoprim, sulfamethoxazole and sulfapyridine antibiotics from mixed solutions. By altering pyrolysis temperature and feedstock, produced biochars yielded a range of physicochemical properties resulting in distinct antibiotic adsorption. Antibiotic adsorption capacity generally decreased with increasing pyrolysis temperature, while adsorption affinities were temperature independent for trimethoprim and increased with pyrolysis temperature for sulfamethoxazole and sulfapyridine. Correlation against biochar properties suggested cation exchange capacity and functional group composition related well to adsorption capacity and polarity/hydrophobicity was linked to adsorption affinities. Antibiotic removal efficiencies by biochars from both feedstocks compared favorably against previous reports, with up to 97.6, 98.1 and 99.5 % of trimethoprim, sulfamethoxazole and sulfapyridine removed, respectively. This work relates biochar production conditions to properties and subsequent antibiotic adsorption, demonstrating application of these materials for removing antibiotics from wastewater.

Variations in composition and stability of biochars derived from different feedstock types at varying pyrolysis temperature

Feedstock type and pyrolysis temperature primarily affect the properties of resultant biochar. Therefore, the effects of several different feedstock types and various pyrolysis temperatures on structural, chemical, proximate, morphological, and elemental compositional characteristics of the resultant biochars were explored. Nine types of wastes (date palm fiber waste (DF), date palm leaf waste (DL), date palm petiole waste (DP), tomato plant waste (TM), cucumber plant waste (CC), poultry litter (PL), chicken feather waste (CH), cow dung (CD), and conocarpus waste (CN) were collected and pyrolyzed at varying temperatures (300, 400, 500, and 600 °C) to produce different types of biochar, which were subjected to physio-chemical, proximate, and ultimate analyses. Distinctive variations were observed in the characteristics of the used feedstock types and their derived biochars. The biochars derived from CC exhibited the highest pH (8.41–11.02), while the biochars derived from CH demonstrated the minimum pH (7.99–8.40). Overall, the biochars derived from PL, CC, TM, and DL showed higher contents of C as compared to the other biochars, suggesting higher stability. Contrarily, the biochars derived from CH and CD exhibited a higher labile C fraction, indicating its lower recalcitrance than other tested biochars. The biochars produced at low pyrolysis temperatures showed a comparatively amorphous surface with lower alkalinity and electrical conductivity, while higher moisture, net negative charge, labile carbon, and volatile contents. Contrarily, the higher pyrolysis temperature demonstrated the higher ash and fixed carbon contents with more surface porosity and comparatively higher non-labile carbon fraction. Biochar produced at 600 °C exhibited H/C and O/C atomic ratios of <0.2, suggesting higher stability and recalcitrant potential against biochars produced below 500 °C, which showed H/C and O/C atomic ratios in the range of 0.2–0.4.

Influence of polymer synthesis route and organic fraction content on structure and porosity of silicon oxycarbide ceramics

This paper describes the structural and textural characteristics of silicon oxycarbide ceramics obtained from three different hybrid polymers by varying pyrolysis temperature. The first polymer was prepared by hydrosilylation between poly(hydromethylsiloxane) and divinylbenzene in stoichiometric proportions; the second was similarly obtained, but with excess of divinylbenzene (60 wt.%) and the third was also synthesized with 60 wt.% divinylbenzene, involving simultaneously hydrosilylation and radical reactions. Precursors were pyrolysed under argon at 1000, 1200 and 1500?C to produce silicon oxycarbide-based ceramics. Silicon carbide phase development and devitrification resistance were influenced by the disordered and ordered residual carbon fraction, which was directly related to the polymer structure. High specific surface area and pore volume values were obtained in C-richer ceramics at 1500?C derived from poly(divinylbenzene) network-containing precursor. Silicon oxycarbide matrices, derived from hybrid polymers containing graphitic carbon and silicon carbide phases together with different amount of porosity, revealed desirable features for electrochemical applications and adsorbent systems.

Optimisation of Biochar Yield from Sorted Wood Wastes as Sustainable Alternatives to Burning to Ash

Abstract Wood wastes are one of the leading contributors of greenhouse gases cum climate change. While the burning of wood wastes results in CO2 emission, decomposition generates methane. In place of these emissions, wood wastes can be converted into biochars which have a lot of novel applications. However, low biochar yield was the common limitation of wood wastes, essentially, due to a mixture of different classifications of trees that pyrolyse at different conditions. In this study, biochar yield from sorted wood wastes was optimised by varying pyrolysis temperature and time. Power consumption, cost, and carbon footprint of the optimised biochar and ash were compared for both hydropower grid and diesel generator scenarios. Optimal pyrolysis yields were 33.6 % (400 °C), 29.4 % (350 °C) and 18.5 % (400 °C) respectively for hardwood sawdust char (HSC), softwood sawdust char (SSC), and mixed sawdust char (MSC) at 2 hours duration for all materials. The CO2 emissions from ash were 2.49 kg and 19.0 kg respectively for grid and diesel power supply. The diesel generator power was 17 times more expensive than grid power for wood wastes pyrolysis. Wood wastes have better biochar yield when charred homogenously; they have a smaller carbon footprint and are cheaper when produced with power from the grid. Wood wastes in place of being burnt can be processed as inexpensive and environment-friendly biochar.

Performance evaluation of crop residue and kitchen waste-derived biochar for eco-efficient removal of arsenic from soils of the Indo-Gangetic plain: A step towards sustainable pollution management

Biochar was produced from wheat straw (Triticum aestivum), rice straw (Oryza sativa), and kitchen waste at varying pyrolysis temperatures (300°C–700 °C). The biochars were screened depending on their production and physicochemical properties for the adsorptive removal of arsenic (As). The morphological analysis by Field emission scanning electron microscope revealed a porous biochar surface. Spectroscopic characterization of biochars indicated the co-existence of minerals, carboxyl, carbonyl, amide, and hydroxyl groups, which implies the suitability of biochar to immobilize metal (loid)s from soils. Changes in peaks were observed in Fourier-transform infrared and X-ray diffraction images after As sorption indicating the involvement of chemisorption. The thermogravimetric analysis and a low H/C value derived from the CHNS analyzer confirmed the high stability of biochar. The BET analysis was used to estimate the surface areas of wheat straw (15.8 m2 g-1), rice straw (12.5 m2 g-1), and kitchen waste (2.57 m2 g-1) -derived biochars. Batch sorption studies were performed to optimize experimental parameters for maximum removal of As. Maximum removal of As was observed for wheat straw-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 initial concentration (IC), 7.5 % dose, 25 °C temperature, and 60 min contact time (83.7 ± 0.06 %); in rice straw-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 IC, 7.5 % dose, 25 °C temperature, 90 min contact time (83.6 ± 0.37 %); and in kitchen waste-derived biochar (pyrolyzed at 500 °C) at 8 mg L−1 IC, 5 % dose, 25 °C temperature, 60 min contact time (76.7 ± 0.16 %). The sorption model parameters suggested the possibility of chemisorption, physisorption, diffusion, and ion exchange for the removal of As. Therefore, it could be recommended to farmers that instead of disposing or burning straws and waste openly, they could adopt the process of charring to generate livelihood security and mitigation of geogenic contaminants from the soil/water dynamic systems.

Char from the co-pyrolysis of Eucalyptus wood and low-density polyethylene for use as high-quality fuel: Influence of process parameters

Providing a valuable application to the under-utilized solid residue of co-pyrolysis of biomass and plastics could substantially improve economic and environmental sustainability of the process, thereby fostering circular economy. This study focuses on the variation of thermal and physiochemical characteristics of solid char, produced from the co-pyrolysis of waste low-density polyethylene (WLDPE) and Eucalyptus wood with varying pyrolysis temperatures from 300 to 550 °C, residence times of 90–150 min, and relative percentage of 33% and 25% (w/w) WLDPE in the feedstock. The highest values of yield (37%), energy density (1.25) and high heat value (31 MJ/Kg) were observed with the char produced at 300 °C. The physical inhibition caused by the overlaying plastic coating on the surface of the char below 450 °C resulted in the same. However, with the increase in temperature, increase in fuel ratio by 78–79% and fixed carbon content by 68–69% were observed. The highest concentrations of fixed carbon (39%), fuel ratio (0.81) along with the lowest O/C and H/C ratios (0.07 and 0.13) were observed with the chars produced above 450 °C depicting their high degree of carbonization. The fuel value indices of all the chars were > 500 GJ/m3 indicating their suitability as high-quality fuels. Significant influences of residence time and feedstock ratio were also observed on properties of the char. The analysis of variance and principal component analysis also depicted significant variations in the properties of the char produced below and above the temperatures of 450 °C due to the inhibitory and synergetic effects. While the chars produced at 300–350 °C could be used for combustion/co-combustion in coal-fired boilers, chars produced above 450 °C can be opted as household fuel due to their low losses of energy, water vapour, and smoke during combustion.