This study explores a novel approach to biochar modification aimed at increasing persistent free radical (PFR) formation on biochar surfaces, thereby enhancing aniline removal via peroxymonosulfate (PMS) activation. By adjusting pyrolysis temperatures and doping ratios, optimal conditions were established. Spearman's analysis highlighted the importance of C=C bonds, the ID/IG ratio, and pyridinic N in generating PFRs. The modified biochar derived at 500 ℃ (MB500), in conjunction with the PMS system demonstrated impressive efficiency, achieving 92% aniline removal within 30 min. Detailed adsorption tests and active species detection indicated that aniline degradation occurred through both direct oxidation by PFRs and indirect oxidation by reactive species, particularly superoxide radicals (O₂⋅⁻). Furthermore, the synergistic effects of heteroatom nitrogen and Na2CO3 modifications significantly impacted PFR formation and stability. These findings provide valuable insights into the mechanisms of PFR-mediated catalytic oxidation, highlighting the key roles of pyridinic rings, with or without oxygenated groups, in enhancing catalytic performance of biochar. This research advances the understanding of biochar surface chemistry and presents an effective strategy for developing high-performance biochar-based catalysts for environmental remediation, addressing the limitations of unmodified biochar through targeted surface modifications.
Accurate estimation of biochar carbon permanence is essential for assessing its effectiveness as a carbon dioxide removal (CDR) strategy. The widely adopted framework, based on the two-pool carbon exponential decay model, forms the basis of policy guidelines and national CDR accounting. However, our re-analysis of the meta-data used in this model reveals significant deficiencies in its parameterization, leading to two critical issues. First, the current parameterization assigns a disproportionally low percentage of the labile carbon fraction (C1) relative to the recalcitrant fraction (C2), effectively reducing the model to a single-pool approach. Due to the limited duration of incubation experiments, the decay constant of the labile fraction is incorrectly applied to the entire biochar mass, resulting in a considerable overestimation of the biochar decay rate. Second, our analysis reveals a lack of causal correlation between the assigned proportions of C1 and C2 and key carbonization parameters such as production temperature and hydrogen-to-carbon (H/C) ratios, suggesting that the model does not accurately represent the underlying chemistry. This misalignment contradicts the established relationship between increased biochar stability and a higher degree of carbonization. Consequently, the the parameterization of current model may not adequately reflect the carbon sequestration potential of biochar. While a multi-pool decay model is suitable for predicting the permanence of biochar, the primary issue with the current model lies in its parameterization rather than its structure. To address these limitations, we recommend that future research prioritize the development of a revised multi-pool decay model with improved parameterization, supported by empirical decomposition data from a variety of experimental methods, including incubation studies, accelerated aging experiments, and comprehensive physicochemical characterization. This refined approach will improve the accuracy of biochar permanence estimations, strengthening its role in global carbon management strategies.
Electrocatalytic oxidation of more stable 2,5-furanedimethanol (FDM) for 2,5-furanediformic acid (FDCA) generation with concurrent hydrogen production is attractive but still nascent compared to 5-Hydroxymethyl-2-furaldehyde (HMF). The need for effective and stable bifunctional electrocatalysts that are efficient for the FDM cell is thus quite significant. Wood serves as an ideal matrix for boosting the performance of catalysts, since its hierarchical porous structures facilitate mass transport and provide abundant active sites. Unfortunately, it has never been demonstrated for electrochemically organic synthesis. Herein, the effectiveness of Fe-CoP in catalyzing FDM oxidation was demonstrated by density functional theory (DFT) calculations and experiments, and a renewable carbonized porous wood decorated with Fe-doped CoP nanoleaves (Fe-CoP/CW) was constructed for electrocatalytic FDCA and hydrogen generation. The obtained Fe-CoP/CW as an anode in FDM solution afforded a current density of 100 mA cm−2 with a yield of 90% FDCA at a potential no more than 1.50 V vs RHE, which was 90 mV and 350 mV lower than Fe-CoP/carbon cloth (CC) and IrO2. In addition, Fe-CoP/CW showed excellent long-term stability for 108-h FDM oxidation in strong alkaline solution. Remarkably, in stark contrast to Fe-CoP/CC and Pt, the hydrogen evolution performance of Fe-CoP/CW was not impacted by FDM at the cathode, and it required exceptionally low overpotentials of 0.19 V to achieve 100 mA cm−2. As a result, in terms of the overall cell, the hydrogen production rate was 0.756 mmol cm−2 h−1, which was 3.57 times higher than those of commonly used commercial Pt | IrO2 cell, presenting a Faraday efficiency of near 100%. This work will pave the way towards the implementation of highly suited bifunctional electrodes and the possibility of affordable, effective, and environmentally-friendly wood-derived electrocatalysts for electrochemically organic synthesis.
This study investigates the adsorption of Brilliant Green (BG) dye onto biochar derived from Syzygium cumini (Jamun) leaves (JLB). Biochar was produced via pyrolysis at 800 °C and examined employing various methods, including Scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, Zeta potential and X-ray photoelectron spectroscopy (XPS). The optimum parameters for BG dye adsorption, determined by batch adsorption studies, were a temperature of 80 °C, an initial dye concentration of 500 mg L−1, a contact period of 30 min, and an agitation speed of 400 RPM. The maximum adsorption capacity of JLB for BG was 243.90 mg g−1. It was found that the adsorption process adhered to the Freundlich isotherm model and pseudo-second-order kinetics, revealing heterogeneous adsorption with chemisorption. A novel "Theory of Pore Conflation" was proposed to explain enhanced adsorption at higher temperatures, supported by SEM and FTIR analyses. Additionally, a new equation termed "Shubhjyot's equation" was introduced to account for time dependency in adsorption capacity calculations. The thermodynamic analysis demonstrated that the process is endothermic and spontaneous. Isopropanol was the most effective organic solvent for desorption studies, demonstrating biochar regeneration potential for up to five cycles. Phytotoxicity and cyto-genotoxicity assessments demonstrated the environmental safety of JLB compared to BG dye. The use of JLB production offers a way to repurpose agricultural waste, contributing to circular economy principles. This extensive study demonstrates JLB's promise as an effective, economical, and environmentally safe adsorbent for wastewater treatment that eliminates textile dyes.
Over the past 10–15 years, biochar has garnered significant global attention in agriculture and environmental science. While most research has focused on the benefits of biochar application in soil enhancement, water quality improvement, and climate change mitigation, the potential risks associated with its use have often been overlooked. This oversight is critical, as the environmental fate of biochar is contingent upon understanding these risks. Once released into the environment, biochar can interact with environmental media, potentially releasing associated pollutants and threatening ecosystems. Therefore, it is essential to evaluate the unintended environmental and health risks associated with biochar during its production and application to select appropriate types for sustainable development. This review was conducted by systematically analyzing and synthesizing relevant studies from Web of Science, focusing on recent advancements and key debates in the field. It categorizes biochar risks into endogenous and exogenous risks based on the source of pollutants carried by biochar. The review analyzes in detail the impacts of raw materials, preparation processes, and application scenarios on the unintended environmental risks of biochar. Furthermore, it provides a thorough overview of the adverse effects on animals, plants, microorganisms, and human health, elucidating the mechanisms of pollutant release, aging, and nano-effects from environmental geochemical processes involving biochar. Additionally, this review summarizes the environmental risk assessment methods of biochar, providing a reference for its safe application and the sustainable development of biochar-related research.
Phosphorus (P) is essential for basic natural processes and can limit the productivity of entire ecosystems. However, agricultural lands worldwide currently suffer from P deficiency. The application of P fertilizers is not only poorly utilized, but also results in the gradual accumulation of P. Biochar, a substance produced by the pyrolysis of biomass under low oxygen levels, is frequently used as a soil amendment. It provides P in a form that is readily available for plant uptake, and thus addresses both short- and long-term soil P deficiencies. In this paper, we systematically reviewed relevant studies on “biochar and soil” or “biochar and soil P” published in the past decade (2013–2023). A synthesis of the reported results revealed that analyzing the effect of biochar on soil P through changes in soil physicochemical properties and microbial communities has gradually emerged as a prominent area of research in recent years. The purpose of this study was to analyze the differential effects of biochar addition on soil P availability, including the clarification of the underlying mechanisms. The results showed that although biochar application generally exerts a positive effect on soil P availability, there are differences in the extent of effects based on application conditions. Shifting to mechanisms, biochar application not only directly increases the available phosphorus (AP) content of soil, but also indirectly influences soil P availability via changes in soil physical, chemical, and biological properties. To summarize, biochar application can affect soil P availability to different degrees through direct or indirect pathways.
Per- and polyfluoroalkyl substances (PFASs), commonly known as ‘‘forever chemicals’’, are persistent organic pollutants that are widely distributed in the environment. Due to their toxicity and resistance to degradation, PFASs are classified as emerging contaminants, and increasing attention is being paid to their remediation. Biochar, an environmentally friendly and cost-effective adsorbent, shows potential for remediating PFASs contamination. The application of biochar for PFASs remediation has garnered growing interest. Compared to other adsorbents, biochar is more economical and the raw materials for its preparation are more readily available. However, there is currently no comprehensive review summarizing the effects of biochar on the environmental behavior of PFASs. This review aims to fill that gap by providing an in-depth discussion and synthesis of the existing literature in this area. It focuses on the environmental behavior of PFASs, specifically addressing the adsorption mechanisms and factors influencing the effectiveness of biochar in PFASs remediation. A proposed mechanism by which biochar photodegrades PFASs through the generation of free radicals, in addition to conventional adsorption mechanisms (such as pore filling, hydrogen bonding, hydrophobic interactions, and electrostatic interactions), is explored. Furthermore, this review discusses the ability of biochar to reduce the likelihood of PFASs entering the food chain through water and soil and evaluates the feasibility and limitations of using biochar for PFASs removal. Finally, we identify future research directions to support the safe and effective use of biochar for PFASs remediation, so as to promote the advancement of green remediation technologies.
Biochar has been proposed as a soil amendment in vegetable fields, where the widespread use of plastic film leads to significant retention of microplastics (MPs) in the soil. However, the interactive effect of biochar and MPs on plant growth and soil functions remains poorly understood. Here, we conducted a pot experiment to examine the effects of biochar application in the presence of conventional and biodegradable microplastics (0.05% w/w) on the growth of coriander, soil nitrogen (N) cycling processes, and microbial communities. The results showed that biochar application increased aboveground biomass by increasing plant available N of NH4 +, regardless of the presence of MPs. Biochar also significantly reduced soil nitrous oxide (N2O) emissions by an average of 16% without MPs. However, when MPs were present, the effect of biochar on N2O emissions was lessened depending on the MP type. Polylactic acid consistently reduced soil N2O emissions and the abundance of N2O production genes, irrespective of biochar application. Conversely, polyethylene without biochar reduced N2O emissions primarily by inhibiting N-related functional genes responsible for nitrification and denitrification. This inhibitory effect was reversed when biochar was applied, leading to a 26% increase in N2O emissions due to increased nifH and nirK gene abundance. Although biochar and MPs did not significantly alter microbial α-diversity, they altered the composition and structure of bacterial and fungal communities, linked to changes in soil N turnover. Our study underscores the critical role of MP type in assessing the effects of biochar on soil N cycling and N2O emissions. Consequently, plastic pollution may complicate the ability of biochar to improve plant growth and soil functions, depending on the characteristics of the MPs.
The increased contamination of potentially toxic element (PTE) has posed remarkable ecological risks to environment. Application of functionalized biochar for the remediation of PTE contaminated water and soils are of great concern, and effective strategies are urgently needed to enhance the removal capacity of biochar for PTE. As a novel surface modification technology, the effect of layered double hydroxides (LDH) and sodium dodecyl sulfonate (SDS) on the remediation capacity of biochar for PTE polluted soils and water remains unclear. Sawdust biochar (SB) was coated with Mg and Fe to synthesize the Mg-Fe-LDH functionalized biochar (MFB); thereafter, the MFB was mixed with SDS solution to synthesize the organic-Mg-Fe-LDH biochar (MSB). The potential of SB, MFB, and MSB for remediation of Cd and Pb contaminated soil and water was evaluated in terms of adsorption capacity, immobilization efficiency, and stability. Loading of Mg-Fe-LDH into SB, along with SDS treatment created a regular micro-nano hierarchical structure and enhanced the surface roughness, aromaticity, and hydrophobicity of MSB as compared to SB. MSB exhibited a significantly higher maximum adsorption capacity (mg g−1) for water Pb (405.2) and Cd (673.0) than MFB (335.9 for Pb and 209.0 for Cd) and SB (178.2 for Pb and 186.1 for Cd). MSB altered the soluble fraction of Cd/Pb to the residual fraction and thus significantly decreased their mobilization in soil. The higher removal/immobilization efficiency of MSB could be attributed to its alkalinity, and the enhanced synergistic interactions including surface precipitation, ion exchange, complexation, and hydrogen bonding. The resistance to carbon loss by H2O2, thermal recalcitrance index R 50, and degree of graphitization in MSB were significantly improved compared to SB, indicating a more stable carbon fraction sequestered in MSB following aging in soil. These results indicate that MSB could be used for remediation of Cd and Pb contaminated soil and water.
The study highlights the critical mechanistic data supporting the ecological restoration advantages of biochar (BC) and its role in sustainable environmental management. Recognizing the substantial influence of specific feedstock sources and pyrolysis parameters on BC efficacy, this research aims to address these gaps through an extensive investigation into the potential benefits of BC application in ecological restoration. The methodology involves a systematic exploration of effects of BC from latest literature on various aspects of agricultural sustainability, including its ability to support crop growth, improve nutrient bioavailability, facilitate co-composting, enhance consumption efficiency, and contribute to water quality restoration. The main results of the study reveal that BC usage results in a net negative carbon (C) footprint, mitigates heavy metal pollution, and enhances soil and ecosystem health. In bioenergy production, BC serves as a versatile resource for generating renewable energy, reducing waste, and facilitating C sequestration. Advanced BC techniques, such as tailored pyrolysis processes and activation methods, further enhance its effectiveness in ecosystem restoration and sustainable resource management. Furthermore, the research identifies deficiencies in current literature and proposes future research directions to advance understanding of BC application. Overall, the study underscores the importance of considering feedstock and pyrolysis variables in BC research and highlights the potential of BC to contribute to ecological sustainability. However, concerns regarding potential health implications for humans in agricultural contexts warrant further investigation and risk assessment to ensure safe and sustainable BC application.
Material selection and production conditions are imperative for determining the functional performances of composite materials. Phase-change composites obtained from phase-change materials (PCMs) and supporting matrices exhibit high thermal energy storage density. They are used to overcome the intermittency issues of wind and solar energy, as well as to reduce waste heat dissipation to the environment. However, the large-scale utilization of composite and pristine materials has severe drawbacks, primarily stemming from the complex fabrication routes of the encapsulating agents, leakage, and inadequate thermal stability. In this study, biochar-based phase-change composites were fabricated using vacuum infiltration techniques, and the effects of biomass feedstock and pyrolysis temperature on the performance of the composite were elucidated using different types of biowastes and temperatures. This approach has several advantages, including facile production techniques, low-cost carbon sources, and environmental friendliness. The PCM adsorption ratio of biochars derived from rice husk (RH) and Miscanthus straw linearly correlated with the pyrolysis temperature (550–700 °C), while RH700 resulted in a composite with a high enthalpy per unit mass of hexadecane (HXD) in RH700/HXD (250.9 J g−1) owing to the high surface area of RH700 (74.66 m2 g−1). The crystalline temperature increased slightly from 10.7 °C in RH550/HXD to 10.9 °C in RH700/HXD, suggesting improved molecular motion and crystal growth of HXD. Wheat straw biomass pyrolyzed at a low temperature (550 °C), displaying a reduced surface area at 700 °C (7.35 m2 g−1) and exhibiting the lowest energy storage density. The latent heat efficiency reached 99.5–100%, where RH700/HXD exhibited 100% efficiency. The composites demonstrated strong leakage resistance at high heating temperatures (60 °C, above the melting temperature of HXD), good chemical compatibility between the biochar and HXD, and high durability after 500 thermal cycles. Therefore, the extent of PCM loading and energy storage density improvements primarily depends on the pyrolysis conditions, feedstock used, and pore size distribution of the biochar samples. This research provides insights into the fabrication of phase-change composites and optimization of the carbonization process of different biomasses used for thermal management applications, such as building energy savings.
Application of advanced techniques and machine learning (ML) for designing and predicting the properties of engineered hydrochar/biochar is of great agro-environmental concern. Carbon (C) stability and phosphorus (P) availability in hydrochar (HC) are among the key limitations as they cannot be accurately predicted by traditional one-factor tests and might be overcome by engineering the pristine HC. Therefore, the aims of this study were (1) to determine the optimal production conditions of engineered swine manure HC with high C stability and P availability, and (2) to develop the best ML models to predict the properties of HC derived from different feedstocks. Pristine- (HC) and FeCl3 impregnated swine manure-derived HC (HC-Fe) were produced by hydrothermal carbonization under different pH (4, 7, and 10), reaction temperature (180, 220, and 260 ℃), and residence time (60, 120, and 180 min) and characterized using thermo-gravimetric, microscopic, and spectroscopic analyses. Also, different ML algorithms were used to model and predict the hydrochar solid yield, properties, and nutrients content. FeCl3 impregnation increased Fe-phosphate content, while it reduced H/C and O/C ratios and hydroxyapatite P content, and therefore improved C stability and P availability in the HC-Fe as compared to HC, particularly under lower pH (4), temperature of 220 ℃, and at 120 min. The generalized additive ML model outperformed the other models for predicting the HC properties with a correlation coefficient of 0.86. The ML analysis showed that the most influential features on the hydrochar C stability were the H and O contents in the biomass, while P availability in HC was more dependent on the C, N and O contents in biomass. These results provided optimal production conditions for Fe-engineered manure hydrochar and identified the best performing ML model for predicting hydrochar properties. The main implication of this study is that it offers a high potential to improve the utilization of biowastes and produce biowaste-derived engineered hydrochar with high C stability and P availability on a large scale.
Biochar is a promising technology for carbon storage and greenhouse gas (GHG) reduction, but optimizing it is challenging due to the complexity of natural systems. Machine learning (ML) and natural language processing (NLP) offer solutions through enhanced data analysis and pattern recognition, ushering in a new era of biochar research.
Considerable carbon emissions from the cement industry pose a notable challenge to achieving long-term sustainable development and creating an enriched social environment. Biochar (BC) obtained from biomass pyrolysis can be used as a carbon-negative material, and it plays a crucial role in the reduction of global carbon emissions. The development of more efficient and cost-effective technologies to fully realize this potential and reduce the environmental impact of BC production and use remains a formidable challenge. The utilization of BC to prepare sustainable cementitious composites with economically value-added benefits has recently attracted much research interest. Therefore, this review analyzes factors influencing the physicochemical properties of BC and their optimization methods, as well as the impact of BC addition on various cement composites and their potential applications. Besides, recent advances in machine learning for predicting the properties of composites and the environmental-economic implications of material are reviewed. The progress and challenges of BC–cement composites are discussed and potential directions for exploration are provided. Therefore, it is recommended to explore commercialization pathways tailored to local conditions and to develop machine learning models for performance prediction and life-cycle analysis, thereby promoting the widespread application of BC in industry and construction.
Biocomposite filaments for material extrusion (MEX) additive manufacturing, particularly those derived from agricultural biomass, have attracted significant research and industrial interest. Biochar is a well-documented reinforcement agent that is used in several polymeric matrices. However, systematic research efforts regarding the quality scores of parts built with MEX 3D printing with biochar-based filaments are marginal. Herein, the impact of biochar loading on the quality metrics of the five most popular polymers for MEX 3D printing (ABS, HDPE, PETG, PP, and PLA) is quantitatively examined in depth. Sophisticated and massive Non-Destructive Tests (NDTs) were conducted, and the impact of biochar loading on the critical quality indicators (CQIs), including porosity, dimensional conformity, and surface roughness, was documented. The quality scores for the biochar filler loading, also five in total, were statistically correlated with the corresponding reinforcement metrics for the five polymeric matrices. A statistically significant antagonistic interaction between the tensile strength course and porosity/dimensional deviation metrics, particularly for PETG, was observed. It can be concluded that the lowest porosity and dimensional deviation are associated with the highest strength. The 4 wt% biocomposite exhibited optimal quality performance in most polymers studied.
Cadmium (Cd) contamination in the environment is widespread, making it crucial to reduce Cd accumulation in cereal crops like wheat. However, strategies that not only mitigate Cd pollution but also address other environmental challenges, such as invasive species management, remain unclear. This study introduces an innovative approach combining molybdenum nanoparticles (Mo NPs, 1 µM) and biochar biofilters derived from the invasive plant Mikania micrantha (IPMM), targeting the biochemical and molecular responses of wheat under Cd stress (100 µM). Our findings showed that this novel combination significantly improved wheat physiological characteristics, growth, root architecture, elemental profile, osmoregulation, carotenoid, chlorophyll, gas exchange, and photosynthetic efficiency. Remarkably, simultaneous supply of IPMM biochar biofilters and Mo NPs substantially modulated the Cd translocation, reducing its accumulation in root (30.54%) and shoot (53.59%). Additionally, this strategy not only preserved mesophyll cell structures and the membrane integrity, but also strengthened and activated the oxidative defense systems through the regulation of genetic expressions. This synergistic approach advances the Cd alleviating techniques and offers a sustainable solution for utilizing invasive plants as a potential resource. By addressing both heavy metal pollution and ecological challenges, it provides a promising solution for safer crop production in Cd-contaminated environments.
This study investigated the application of biochar and microbial-inoculated biochar in municipal solid waste (MSW) composting to enhance and accelerate the process. Microbial consortium from the active composting phase was utilized for inoculation and biofilm formation on the biochar surface. Five experimental windrow piles were established, including a control pile without biochar, and piles amended with either biochar or microbial-inoculated biochar. The composting process and the quality of the final product were evaluated by analyzing a range of physicochemical and biological parameters. The results demonstrated that piles amended with inoculated biochar exhibited higher levels of FDA hydrolytic activity and organic matter reduction, indicating enhanced microbial activity. Notably, piles 3 and 5, amended with biochar inoculated with a bacterial consortium and a bacterial-fungal consortium, respectively, achieved the highest composting temperatures (65 °C) and produced the highest-quality end products (C/N ratio: 10.1–11.8, Germination index: 100, and fecal coliform levels within acceptable limits) compared to the control piles. These findings provide valuable insights into the practical application of microbial-inoculated biochar in the real field of MSW composting, offering a promising approach to optimize composting efficiency and product quality.
The effects of biochar on methane emissions from soils are well understood. However, biochar effects on methane production from livestock have received less attention. In this study, a biochar-mineral supplement for livestock was developed by pyrolyzing a mixture of wheat straw, aluminosilicates, iron sulfate, and zinc oxide at 600 ℃. The supplement was then activated using peracetic and propionic acids, and potassium nitrate. The activated biochar-mineral supplement was characterized using analytical techniques. A high surface area, a high concentration of oxygen-containing functional groups, and a high concentration of free radicals, associated with O and Fe unpaired electrons, assisted the supplement with catalysing the oxidation of methane. Microstructural analysis of the supplement suggested the formation of organo-mineral phases, rich in C, O, Fe, Si, Al, K and Ca, indicating that the biochar reacted with mineral additives to preserve them. To assess the potential of the supplement to reduce methane produced form livestock, an in vitro batch culture incubation was conducted (n = 3) with rumen fluid sourced from Holstein–Friesian steers. The supplement was incubated at inclusion rates of 0% (control), 1.5%, 4.0% and 6.0% of dry matter (DM), with a Rhodes grass hay substrate. Compared to the control, the supplement reduced cumulative gas production by 10.1% and 12.7% and methane production by 19.03% and 29.32% after 48 h when included at 4.0% and 6.0% DM (P < 0.05), respectively, without causing any detrimental impacts on fermentation parameters. The supplement assisted with reducing the concentration of dissolved mineral nutrients, such as P and Mg, when included at 4.0% and 6.0% DM (P < 0.05).
Climate change and unbalanced energy demand and consumption require innovative approaches to the development of sustainable and renewable energy technologies. Phase change materials (PCMs) present exceptional solutions for zero-energy thermal management due to their outstanding energy storage density at an isothermal phase transition. However, the low thermal transport and thermal stability of bulk PCMs, as well as the expensive and complex synthesis of additive materials, hinder their large-scale utilization. In this study, food-waste-derived engineered biochar (FW) is produced via slow pyrolysis to improve the thermal properties of a microencapsulated bio-PCM (B28). The thermal performance of biochar-PCM composites is evaluated based on two biochar preparation systems: varying activation temperatures (carbonized at 400 °C followed by KOH activation at different temperatures (500–800 °C)) and varying mass ratios between KOH and biochar. The introduction of a low (0.63 wt%) engineered biochar dopant significantly improves the thermal diffusivity of B28 by more than 1.3-fold. The biochar-PCM microcapsule composites present fusion and crystalline isothermal phase transition temperatures of 29.4 ± 0.38 °C and 16.7 ± 0.13 °C, respectively. Moreover, the bio-PCM exhibits a highly efficient energy per unit mass of 61.6 kJ kg–1, which is 101.7% of the energy storage capacity of bulk B28. Additionally, the composite demonstrates high thermal stability with decomposition occurring above 195 °C, thus enabling an increase of > 20 °C in the onset decomposition point compared with pristine B28. Further analysis reveals the impact of the KOH/biochar mass ratio on the thermal properties of bio-PCM. Sample FW6PCM, in which the biochar is activated at 600 °C with a KOH/biochar mass ratio of 1, exhibits the highest enthalpy storage capacity. This study suggests a promising strategy for designing high-performance, eco-friendly, and scalable bio-based composite PCMs by overcoming the long-standing bottleneck of microcapsules, which is crucial for advanced thermal management applications such as cooling and green buildings.
Persistent free radicals (PFRs) in biochar have attracted wide attention due to their multifaceted roles in the environment. The regulation of PFRs in biochar is not only beneficial to broaden its application potential, but also eliminates its environmental risks. However, as a common biochar modification reagent, phosphoric acid (H3PO4) has not been studied in the field of PFRs regulation. Herein, this study systematically investigated the effect of H3PO4 on PFRs in biochar under various conditions. The results indicated that H3PO4 promoted the formation of PFRs in biochar at low pyrolysis temperature (< 500 °C), owing to the positive effect of catalytic cross-linking on the degradation of biomass precursor. Yet, H3PO4 reduced PFRs in biochar at high pyrolysis temperature (≥ 500 °C), since the capture of H∙ or HO∙ by PO∙ and the steric hindrance changed by H3PO4, which caused the rearrangement and polycondensation of carbon structure. H3PO4 also favored carbon-centered PFRs as the dominant type. The ingredients of biomass precursor, including cellulose, Fe, Ti, protein, etc., contributed to different effects on PFRs under H3PO4 modification. This study provided new insights into the roles of H3PO4 on the formation and transformation of PFRs in biochar, coupled with regulation strategies in the practical application.
In this research, a novel metal-organic framework-modified biochar composite (MIL-88b@BC) was created for the first time by modifying rice husk biochar using the excellent adsorption properties of metal-organic framework (MOF), as well as reducing the solubility of MOF using biochar as a substrate, aiming to improve the understanding of the adsorption characteristics of rare-earth metal recycling and to predict its adsorption mechanism. Density functional theory (DFT) computations allowed for rationally constructing the adsorption model. According to DFT calculations, the primary processes involved in the adsorption of La3+ were π–π interaction and ligand exchange, wherein the surface hydroxyl group played a crucial role. MIL-88b@BC interacted better with La3+ than biochar or MOF did. Accompanying batch tests with the theoretical conjecture's verification demonstrated that the pseudo-second-order model and the Langmuir model, respectively, provided a good fit for the adsorption kinetics and isotherms. The maximum La3+ adsorption capacity of MOF@BC (288.89 mg g−1) was achieved at pH 6.0, which was significantly higher than the adsorbents' previously documented adsorption capacities. Confirming the DFT estimations, the adsorption capacity of BC@MIL-88b for La3+ was higher than that of MOF and BC. Additionally, MOF@BC can be recycled at least four times. To mitigate the growing scarcity of rare earth elements (REEs) and lessen their negative environmental effects, this work laid the path for effectively treating substantial volumes of wastewater produced while mining REEs.
Highlights
| • | The novel composite adsorbent was prepared by MOF and biochar in situ growth method. |
| • | The adsorption mechanism was innovatively investigated based on DFT calculations. |
| • | Ligand exchange and La–O–Fe formation dominated in lanthanide ion removal. |
The enhancement of saline soil yield potential by biochar was well-documented, but the changes brought by biochar particle size on soil properties and crop performance are not well understood. To investigate the changes in soil properties and tomato yield due to biochar particle size under varying salt stress, we conducted a pot experiment in China Northwest’s solar greenhouse. A total of nine treatments were applied, with three different salt amounts of [S0 (no salt), S1 (0.3% dry weight), and S2 (0.6% dry weight)], and three biochar treatments of B0, B1, and B2 (0, 0.5% of large particles and 0.5% of small particles). Adding biochar did not significantly affect the measured soil chemical properties, except for pH, total nitrogen (TN), and Ca2+. Specifically, the addition of biochar significantly increased soil pH and TN, while reduced soil Ca2⁺ content likely due to biochar selective adsorption of Ca2⁺. Biochar particle size had opposite effects on tomato yield under varying salt stress levels. Compared to S0, the yield under B1 was 19.1% and 36.5% higher, whereas under B2, the yield was 33.1% and 44.2% lower for S1 and S2, respectively. Under no salt stress, small-size biochar increased yield by 51.0% compared to B0, largely due to the improved soil water and nutrient status. These results are of great value for developing better strategies for adding biochar with appropriate properties into saline soils to achieve greater productivity gains.
Highlights
| • | Biochar addition significantly reduced soil Ca2+ by 16.7–37.9%, while there was no significant difference in the other cations. |
| • | Large-size biochar alleviated salt stress and improved tomato yield by promoting salt leaching and enhancing soil nutrients. |
| • | Small particle size biochar exacerbated salinity stress and reduced tomato yield under higher salinity treatments. |
| • | Small particle size biochar boosted tomato yield in soils without salinity stress. |