Physicochemical Properties Of Biochar Research Articles

Tailoring the Biochar Physicochemical Properties Using a Friendly Eco-Method and Its Application on the Oxidation of the Drug Losartan through Persulfate Activation

In this study, spent malt rootlet-derived biochar was modified by a friendly eco-method using a low temperature (100 °C) and dilute acid, base, or water. The modification significantly enhanced the surface area from 100 to 308–428 m2g−1 and changed the morphology and the carbon phase. In addition, the mineral’s percentage and zero-point charge were significantly affected. Among the examined materials, the acid-treated biochar exhibited higher degradation of the drug losartan in the presence of persulfate. Interestingly, the biochar acted as an adsorbent at pH 3, whereas at pH = 5.6 and 10, the apparent kinetic constant’s ratio koxidation/kadsorption was 3.73 ± 0.03, demonstrating losartan oxidation. Scavenging experiments indirectly demonstrated that the role of the non-radical mechanism (singlet oxygen) was crucial; however, sulfate and hydroxyl radicals also significantly participated in the oxidation of losartan. Experiments in secondary effluent resulted in decreased efficiency in comparison to pure water; this is ascribed to the competition between the actual water matrix constituents and the target compound for the active biochar sites and reactive species.

"Preparation and characterization of biochar from four types of waste biomass under matched conditions

Four contrasting types of waste biomass were subjected to matching treatments to prepare biochar for the potential removal or immobility Cr(VI) in polluted water or soil. Rice straw (RS), rice husk (RH), kraft lignin (KL), and cow dung (CD) were selected. The resulting biochars were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and N2 adsorption-desorption isotherms. The physicochemical properties of biochars, such as pH value, ash, yield, and cation exchange capacity (CEC) were also determined. The results showed that the biochars were alkaline, except for the KL biochar (KLBC), which was weakly acidic. Furthermore, the order of CEC was cow dung biochar (CDBC) > rice straw biochar (RSBC) > rice husk biochar (RHBC) > KLBC. FTIR showed that there are abundant oxygen-containing functional groups on the surface of the biochars, with the total amount almost the same, and the structure was dominated by aromatic ring skeleton. The KLBC with micro-nano structure exhibited higher surface area (111 m2/g) than the other BC samples. The Cr(VI) removal followed the order: KLBC > CDBC > RHBC > RSBC.

Biochar a Promising Strategy for Pesticide-Contaminated Soils

Soil pesticide contamination induced by modern agriculture has become a serious global issue. Its uncontrolled and inefficient application is among the main reasons for their enrichment in plants and animals subsequently transferred to humans and providing a public health risk. Biochar as a renewable and economical carbonaceous material provides a natural solution for immobilizing pesticides and improving soil health. The biochar impact in agricultural contaminated soil is governed by various factors such as the physico-chemical properties of biochar, pyrolysis, soil conditions, and the application method, which can lead to significant gaps in the removal or mitigation of toxic substances. The current study summarizes the negative effects of pesticide use and the advantages of biochar according to other remediation techniques, succeeded by the mechanism and controlling factors on minimizing pesticide leaching and bioavailability in soil. In addition, the role of biochar on fundamental processes of adsorption, desorption, biodegradation, and leaching is discussed. Ultimately, the major future research regulation and key strategies that are fundamental for pesticide-contaminated soil remediation are proposed.

Study of soil nitrogen cycling processes based on the 15N isotope tracking technique in the black soil areas

In recent years, biochar has been widely used for soil improvement, but there has been some variation in its effectiveness; the mechanism of regulating nutrient cycling in soil is unclear due to different soil textures and physicochemical properties of biochar. Therefore, in this paper, the effects of different tillage patterns and biochar gradients on the nitrogen use efficiency (NUE) and soil nitrogen fixation capacity of soybean were monitored in a phased manner by field trials using 15N isotope tracer technology. The results of the study showed that (1) biochar increases the soil's nitrogen fixation capacity by improving the structural stability of the soil. Total nitrogen (TN) content of the soil increased by 42% after deep ploughing (DP) application of 500 kg/acre of biochar. (2) Biochar improved the nitrogen use efficiency of soybean plants and increased soybean yield. Compared to that of shallow tillage (SP), deep tillage application of 500 kg/acre of biochar increased the nitrogen use efficiency of soybean by 0.62–3.45%. 15N isotope tracking technology showed that soybean plants with deep tillage application of 500 kg/acre of biochar had the highest 15N content at flowering stage; compared to no biochar application, the 15N content of root, stem and leaf fractions increased by 65.4–86.9%. (3) Biochar increased soil CO2 emission fluxes, reduced soil CH4 emission fluxes and soil N2O emission fluxes, with better GHG emission reduction under DP treatment. The regulation model of deep ploughing application of 500kg/acre of biochar provides a reference and guiding meaning for future soil fertility maintenance and farmland soil tillage in black soil areas.

Customized biochar for soil applications in arid land: Effect of feedstock type and pyrolysis temperature on soil microbial enumeration and respiration

Biochar is rapidly gaining worldwide interest as an agro-technology for increasing soil health and carbon storage. This study investigated the physicochemical characteristics and impact on soil microbes of biochar amendments from three feedstock sources: date palm leaves (D), mesquite plants (M) and sludge compost (S.C.); pyrolyzed at 450 ℃, 600 ℃ and 750 ℃. Scanning electron microscopy images showed an apparent pore size increase with increasing pyrolysis temperature. The increase in pyrolysis temperature decreased O-H and C-O bonds and increased the proportion of C-C bonds, as obtained from the Fourier transform infrared spectroscopy studies. Thermostability was highest at a pyrolysis temperature of 750 ℃, with distinct thermal decomposition profiles for each of the three feedstock materials used, as indicated by the dynamic thermal gravimetric analysis. The SC biochars showed the highest mineral content (45–66%) with significantly higher water-soluble and total concentrations of mineral elements. The SC samples also showed the presence of possible soil contaminants such as Pb and As, and its use as a soil amendment is not recommended, even though the SC at 450 ℃ was the only nonalkaline biochar in this study. The M feedstock produced biochar with the highest surface area (600 m2 g−1) and carbon content based on loss on ignition (94.98%); nevertheless, the M biochar reduced soil microbial enumeration and respiration. This reduction increased with increasing pyrolysis temperature. Therefore, the M biochar feedstocks are not recommended for improving soil health and may be tested in the future as a microbial inhibitor for soil-borne plant pathogens. Considering the physicochemical properties and the biochar impact on soil, D at 600 ℃ was the best biochar selected for further studies as a soil amendment. The large differences in biochar physicochemical properties and their effect on soil microbes observed in this study suggest that the feedstock type and pyrolysis temperatures must be considered during biochar amendment production for improving soil health in arid-land agroecosystems.

Preparation of sludge-corn stalk biochar and its enhanced anaerobic fermentation

In order to realize efficient utilization of stalk and sludge, mixed biochar was prepared from corn stalk and sludge to optimize the characteristics of anaerobic fermentation gas production. The mixed biochar was prepared under different carbonization temperature, raw material ratio, heat preservation time and heating rate, and was added to anaerobic fermentation as a supplement, the relationship between the physicochemical properties of biochar and anaerobic fermentation performance was investigated. The findings revealed that methane production up to 269.23 mL/g VS when the carbonization temperature was 600 °C, the ratio of raw materials was 1:1, the holding time was 90 min and the heating rate was 10 °C/min, and compared with the addition of pure sludge, pure corn stalk and blank control group, the cumulative methane production increased by 36.13%, 37.32% and 47.1% respectively. The biochar's particular surface area and pore structure only affect methane production in a certain range. The link between the characteristics of carbon materials and the generation of methane through anaerobic fermentation is further studied using the theoretical framework provided by this study.

Influence of indirectly heated steam-blown gasification process conditions on biochar physico-chemical properties

Our work provides a thorough characterization of different biochars produced by a novel 50 kWth Indirectly Heated Bubbling Fluidized Bed Steam Reformer. This study investigates the effect of temperature and gasification agent on the physico-chemical properties of biochars. We combined macro, micro and nano characterization techniques to provide a clear picture of the biochar characteristics, surface functionality and its “inert” nature toward potential applications. Our results demonstrate that indirect gasification is capable of producing carbon-rich biochars (> 92%) with increased porosity (89–198 cm3.g−1), high heating value (28–31 MJ.kg−1 a.r.) and aromaticity compared to the parent biomass. All biochars have lower O/C (0.02–0.04) and H/C atomic ratios (0.09–0.19), similar to anthracite. For the range of tested gasification conditions, air/steam gasification at an equivalence ratio of 0.20 and steam-to-biomass ratio of 1.2 provides the highest biochar yield (7.3%), while maintaining syngas composition optimal. On the other hand, air gasification produces biochars with relatively high content of inorganic elements. Indirectly heated biochars are compliant with the European Biochar Certificate regarding the carbon content, O/C ratio, H/C ratio. Our biochars may provide an improvement in agricultural yield and CO2 adsorption, especially those produced under air/steam gasification conditions. Our novel indirect design not only constitutes a promising development in the field of biomass allothermal gasification but also can help improving gasification circularity through the production of high quality biochar.

Synthesis of Biochar From Lignocellulosic Biomass for Diverse Industrial Applications and Energy Harvesting: Effects of Pyrolysis Conditions on the Physicochemical Properties of Biochar

The excessive dependency on fossil fuel resources could be curtailed by the efficient conversion of lignocellulosic biomass. Biochar, a porous carbonaceous product synthesized exploiting thermochemical conversion pathway, could be an environment-friendly replacement of fossil fuel resources. Slow pyrolysis, a sub-class among various thermochemical conversion techniques, has gained immense popularity owing to its potential to convert biomass to biochar. Furthermore, biochar obtained as the by-product of slow pyrolysis has attracted enormous popularity due to its proven role and application in the multidisciplinary areas of engineering and environmental remediation applications. The physicochemical quality of biochar and its performance is significantly dependent on the feedstock type and pyrolysis process parameters. Therefore, further experimental research and investigations in terms of lignocellulose biomass type and pyrolytic process parameters (temperature, heating rate and reaction time) are essential to produce biochar with desired physicochemical features for effective utilization. This review presents an updated report on slow pyrolysis of lignocellulosic biomass, impact of different pyrolysis parameters and degradation pathway involved in the evolution properties of biomass. The influence of the feedstock type and lignocellulosic composition on the biochar properties are also discussed meticulously. The co-relationship between biochar yield at different pyrolysis temperatures and the development of textural properties provides valuable information for their effective utilization as a functional carbon material. Additionally, an extensive study was undertaken to collate and discuss the excellent physicochemical characteristics of biochar and summarizes the benefits of biochar application for diverse industrial purposes. Biochar is acknowledged for its excellent physicochemical properties owing to the thermal treatment and as a result its prospective diverse industrial applications such as for soil treatment, carbon sequestration, adsorbent (wastewater treatment or CO2 capture), producing activated carbon for gold recovery, energy storage and supercapacitor are summarized systematically in this review paper. For instance, biochar when applied in soil have shown improvement in soil respiration by 1.9 times. Furthermore, biochar when used to capture CO2 from flue gas stream under post-combustion scenario has demonstrated superior capture performance (2.8 mmol/g) compared to commercial activated carbon. This paper identified the knowledge gaps and outlooks in the field of the advancements of biochar from slow pyrolysis for targeted engineering applications mainly in the field of environmental remediation and energy harvesting.

Fluoride-contaminated water remediation using biochar derived from dairy processing sludge

Seeking a technically reliable disposal platform for milk sludge has drawn particular concern considering its hazardous potential to our environment. Milk sludge from the dissolved air flotation process has abundant calcium because of the naturally available calcium in milk and lime addition as a coagulant. No previous study on its ability to remove fluoride based on its abundant calcium has been reported. As a strategic measure to minimize the environmental impacts, milk sludge was pyrolyzed. Milk sludge biochar was used as an adsorbent to remove fluoride from water. To delineate the close relationships between the fluoride removal capacity and the physico-chemical properties of biochar, milk sludge biochar was fabricated at the temperature range from 500 to 800 ˚C. In an effort to align the experimental/theoretical data, adsorption kinetics, isotherms, column studies, and equilibrium modelling using visual MINTEQ 3.1 were conducted. In addition, milk sludge biochar was characterized using field-emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Biochar fabricated at 800 °C (MS800) exhibited the highest fluoride removal capacity of 485.9 mg/g. Only MS800 mainly composed highly soluble Ca(OH)2 while the other temperature-prepared biochar mainly composed of less soluble CaCO3. Consequently, MS800 is providing more Ca2+ to the system. At the equilibrium, MS800 releases Ca2+ ∼200 mg/g into water within 24 h. X-ray diffraction of the spent biochar shows that fluoride was removed by forming a CaF2 precipitation. All experimental findings of this study confirmed that milk sludge converted into a value-added, efficient environmental media to remediate fluoride-contaminated wastewater.

Effects of physical and chemical aging on polycyclic aromatic hydrocarbon (PAH) content and potential toxicity in rice straw biochars.

Polycyclic aromatic hydrocarbons in biochars threaten their environmental application. The aging process may affect the concentration of PAHs, potential toxicity, and the properties of biochar. In this study, the aged biochars were obtained by simulated physical aging method (freeze-thaw treatment) and chemical aging method (H2O2 chemical oxidation). The PAH contents in biochars were measured, and their potential toxicity was assessed. Meanwhile, the influence of aging process on the physicochemical properties of biochar was also investigated. This study shows that the change of PAH content of aged biochars depended on pyrolysis temperature, ambient temperature, and oxidant concentration. Furthermore, physical and chemical aging process influenced the distribution of different ring PAHs in biochars. High-ring-number PAHs (four, five, six-ring PAHs) appeared in some aged biochar. Aging at ±20 °C and 0.01 M H2O2 increased the toxic equivalent quantity of all biochars which may be attributed to the change of the physicochemical properties influencing the different PAH ring distribution in biochars. The contribution of PAHs with different rings to TEQ varied in pristine and aged biochars. Physical and chemical aging process significantly affected the properties of biochars, such as element content, ash content, surface area, pore volume, pH, functional groups, and surface morphology. Correlation analysis confirmed that surface area and pore volume are dominant factors determining the PAH content in the biochars. Therefore, the aging process indeed affected the PAH concentration and toxicity of PAHs in biochar. Assessing PAH behavior in biochar over long timescales should not be overlooked.

Toxicity of biochar influenced by aging time and environmental factors

The extensive application of biochar has drawn more attentions on its potential risk to aquatic organisms. However, the influence of environmental factors (i.e. pH, HA, SDBS and aging time) after they discharged into environment on their toxicity have not been clarified. Here, we synthesized biochar with local pine needles via pyrolysis, and then aged in different media. Followed, the toxicity of pristine and aged biochar was checked with Scenedesmus obliquus (S. obliquus). Our investigation showed that the toxicity of biochar was mitigated when aged in different pH levels or SDBS, while it was opposite in the presence of HA. The increment of pH decreased the toxicity of both the pristine and the aged biochar, while the presence of HA did same impact on the pristine biochar. The presence of SDBS decreased the toxicity of pristine biochar but increased that of aged biochar. Meanwhile, we showed these environmental factors (pH, HA, SDBS and aging time) influenced the biochar toxicity may be due to the adjustment of the aggregation and adhesion of biochar on cell surfaces or the intracellular oxidative stress. Further, the PFRs contained in biochar did influence the toxicity, along with the physicochemical properties of biochar (i.e. carbon structure, functional group or surface charge). Our results aimed to reflect the toxicity profile of biochar in the natural aquatic environment, without misunderstanding of potential ecological risk of biochar in the future application.

Co-Pyrolysis of Sewage Sludge and Wetland Biomass Waste for Biochar Production: Behaviors of Phosphorus and Heavy Metals.

Large amounts of sewage sludge (SS) and wetland plant wastes are generated in the wastewater treatment system worldwide. The conversion of these solid wastes into biochar through co-pyrolysis could be a promising resource utilization scheme. In this study, biochar was prepared by co-pyrolysis of SS and reed (Phragmites australis, RD) using a modified muffle furnace device under different temperatures (300, 500, and 700 °C) and with different mixing ratios (25, 50, and 75 wt.% RD). The physicochemical properties of biochar and the transformation behaviors of phosphorus (P) and heavy metals during the co-pyrolysis process were studied. Compared with single SS pyrolysis, the biochar derived from SS-RD co-pyrolysis had lower yield and ash content, higher pH, C content, and aromatic structure. The addition of RD could reduce the total P content of biochar and promote the transformation from non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP). In addition, co-pyrolysis also reduced the content and toxicity of heavy metals in biochar. Therefore, co-pyrolysis could be a promising strategy to achieve the simultaneous treatment of SS and RD, as well as the production of value-added biochar.

Changes in Physicochemical Properties of Biochar after Addition to Soil

It is recognized that biochar undergoes changes when it is applied to soils. However, the mechanisms of biochar alterations are not fully understood yet. To this purpose, the present study is designed to investigate the transformations in the soil of two different biochars obtained from pyrolysis of fir-wood pellets. The production of the biochars differed for the dry and wet quenching procedures used to terminate the pyrolysis. Both biochars were applied to clay soil (26% sand, 6% silt, and 68% clay) placed into lysimeters. After water saturation and 15 days of equilibration, seeds of watercress (Lepidium sativum) were cultivated. After a further 7 weeks, the biochars were manually separated from the systems. A total of four samples were collected. They were analyzed for chemical–physical characteristics by using an innovative technique referred to as fast field cycling nuclear magnetic resonance relaxometry. The results showed that the dry−quenching produced a material that was mainly chemically altered after application to soil compared to the biochar obtained by the wet−quenching. Indeed, the latter was both chemically and physically modified. In particular, results showed that water was better retained in the soil treated with the dry−quenched material. Consequently, we may suggest that crop productivity and environmental remediation may be modulated by applying either the dry−quenched or the wet−quenched biochar.

Real wastewater micropollutant removal by wood waste biomass biochars: A mechanistic interpretation related to various biochar physico-chemical properties

Emerging organic micropollutants (OMPs) are ubiquitous in waterbodies and not fully eliminated by wastewater treatment plants (WWTP). A proposed WWTP upgrade includes OMPs sorption by biochar rather than activated carbon (AC). Activated biochar (AB) and non-activated biochar (NAB) sorption performance towards 4 target OMPs (benzotriazole, sulfamethoxazole, carbamazepine, diclofenac) were evaluated in real-wastewater. Sorption processes are discussed in light of sorption mechanisms that depend both on OMP and on biochar physico-chemical properties. AB and AC have similar average sorption efficiency (45%), while NABs are much less efficient (<19%). OMPs sorption significantly correlates to SSA, inversely to H/C (indicating hydrophobic interaction with graphene-like structures) and to CEC or ash content (indicating H-bond or ternary surface complexation sorption mechanisms). This highlights the need to mix AB sources with different physico-chemical characteristics to sorb a large OMP spectrum within WWTPs. Production and use of ABs alleviate the negative environmental impact of ACs.

Efficacy of rice straw derived biochar for removal of Pb+2 and Zn+2 from aqueous: Adsorption, thermodynamic and cost analysis

The conversion of rice straw to biochar through pyrolysis can produce a low-cost and efficient adsorbent that removes metal contaminants from the aqueous. Biochar was derived at various pyrolysis temperatures (300–500 °C) and analyzed the physicochemical properties. The physicochemical properties of biochar, including pH (8.23–10.25), surface area (12.78–64.56 m2/g), and surface morphology were enhanced at a higher temperature. Biochar produced at 500 °C indicated the highest adsorption of Pb+2 (17.93 mg g−1) and Zn+2 (25.73 mg g−1). The Pseudo-second order and Langmuir isotherm were the best fit for the experimental data. The negative value of Gibbs free energy signified that the sorption was thermodynamically viable and of a spontaneous process. The cation exchange played a major role in adsorption, contributing to about 60 and 70% of total Pb+2 and Zn+2 adsorption. Cost assessment of biochar production validated its cost viability compared to commercially accessible adsorbents.

An overview on biochar production, its implications, and mechanisms of biochar-induced amelioration of soil and plant characteristics

The degradation of soil fertility and quality due to rapid industrialization and human activities has stimulated interest in the rehabilitation of low-fertility soils to sustainably improve crop yield. In this regard, biochar has emerged as an effective multi-beneficial additive that can be used as a medium for the amelioration of soil properties and plant growth. The current review highlights the methods and conditions for biochar production and the effects of pyrolysis temperature, feedstock type, and retention time on the physicochemical properties of biochar. We also discuss the impact of biochar as a soil amendment with respect to enhancing soil physical ( e.g. , surface area, porosity, ion exchange, and water-holding capacity) and chemical ( e.g. , pH, nutrient exchange, functional groups, and carbon sequestration) properties, improving the soil microbiome for increased plant nutrient uptake and growth, reducing greenhouse gas emissions, minimizing infectious diseases in plants, and facilitating the remediation of heavy metal-contaminated soils. The possible mechanisms for biochar-induced amelioration of soil and plant characteristics are also described, and we consider the challenges associated with biochar utilization. The findings discussed in this review support the feasibility of expending the application of biochar to improve degraded soils in industrial and saline-alkali regions, thereby increasing the usable amount of cultivated soil. Future research should include long-term field experiments and studies on biochar production and environmental risk management to optimize biochar performance for specific soil remediation purposes.

Evaluation of the potential of feedstock combinations and their biochars for soil amendment.

One of the approaches for recycling and reusing agricultural and animal wastes is to pyrolyse the residues and subsequently use them as soil amendments. The prevalence of several feedstocks suggests that it is necessary to investigate the optimal combinations of feedstocks and pyrolysis temperature for use as soil amendments. This study was done to evaluate five combinations of raw materials (sugarcane bagasse, rice husk, cow manure and pine wood) and their biochars produced by slow pyrolysis at 300°C and 500°C for soil amendment. Several physicochemical properties (electrical conductivity (EC), pH, cation exchange capacity (CEC), total organic matter content (C) total porosity (TP), total nitrogen (N), particle density (PD) and bulk density (BD)) were investigated. Comparison among feedstocks showed that the highest PD, BD and CEC were observed in WM (cow manure-pine wood). The pyrolysis process increased the PD, TP, N and monovalent cations and decreased EC, CEC and BD. Compared to the feedstock, pyrolysis increased the N content, but higher temperatures lowered the N content. Pyrolysis at 500°C reduced the EC, N, CEC and biochar yield by 18%, 13%, 21% and 24% respectively, compared to 300°C. Pyrolysis at 500°C increased the pH, Na+ and K+ by 17%, 12% and 22%, respectively, compared to 300°C. Considering the physicochemical properties of biochar and the costs, the bagasse-wood-rice (BWR) combination and temperature of 300°C are suggested for biochar production for soil amendment.

Application of the engineered sewage sludge-derived biochar to minimize water eutrophication by removal of ammonium and phosphate ions from water

Engineered biochars obtained by pyrolysis of sewage sludge (SSL) are interesting materials that are worth investigating both in terms of nutrients adsorption and their re-usage in agriculture. In the present study, single- or bi-solute adsorption of phosphate and ammonium ions on biochars was performed. The biochars were produced from SSL or from SSL and willow (6:4 w/w) at temperatures of 500, 600, and 700 °C. During the pyrolysis process, two different carrier gases were used: N2 or CO2. After adsorption, desorption of the studied ions was carried out using deionized water (DI). The Langmuir isotherm (R2 > 0.805) best described the adsorption of phosphate ions on all biochars and ammonium ions on the biochars produced from SSL alone. Willow addition to SSL caused the change in the ammonium ions sorption mechanism to Freundlich model (R2 > 0.861). The SSL-derived biochar (700 °C; N2 atmosphere; single-solute adsorption) was characterized by the highest theoretical phosphate ions sorption capacity (88.1 mg/g), which was associated with development of the specific surface area (SBET) and a high content of the inorganic fraction and metals. The SSL and willow-derived biochar (500 °C; N2 atmosphere; single-solute adsorption) had the highest ability to bind ammonium ions (36.0 mg/g), which was dependent on the density of functional groups. Desorption of ions was dependent on adsorption mechanism, physico-chemical properties of biochars and adsorption system. The maximum desorption of phosphate ions (44.8%) was observed for SSL-derived biochars (bi-solute adsorption; 500 °C), while in the case of ammonium ions (20.1%) for the SSL and willow-derived biochars (bi-solute adsorption; 700 °C). Replacing N2 with CO2 during pyrolysis caused higher desorption of phosphate and ammonium ions. Thus, re-use of SSL and willow-derived biochar produced at N2 atmosphere (after adsorption process) in agriculture may regulate the mobility and availability of nutrients (particularly in the case of phosphate ions), due to their lower but longer release rate compared to biochar from SSL alone.

Impact of deashing treatment on biochar physicochemical properties and sorption mechanisms of naphthalene and 1-naphthol

To elucidate the mechanisms controlling mineral effects of biochars on sorption of organic pollutants (OPs), sorption kinetics and isotherms of naphthalene and 1-naphthol on both pristine and deashed rice straw-derived biochars obtained at 200, 400 and 600 ºC were investigated. The organic carbon-normalized distribution coefficients (Koc) and equilibrium sorption capacity (Qe) of naphthalene and 1-naphthol by biochars generally increased after deashing. This was principally because mineral removal caused less exposure of polar groups, especially the O-alkyl components, on biochar surfaces and enhancement of hydrophobic sorption domains, thus mainly facilitating hydrophobic interactions between the compounds and aromatic components within biochars relative to the alkyl carbon components. The removal of minerals in biochars, which reduced the surface polar groups, promoted diffusion of naphthalene molecules toward the surface hydrophobic domains, thereby increasing its sorption rate constant for the fast-sorbing fraction on biochars (kfast). In contrast, the kfast values of 1-naphthol decreased after deashing, which could be ascribed to the weakened fast sorption via H-bond between 1-naphthol and mineral O-containing surfaces or polar groups on biochar surfaces. Both compounds exhibited lower rate constants for the slowly sorbing fraction (kslow) on deashed biochars, which had higher aromaticity and larger porosity and surface area than the raw biochars and inhibited the diffusion of sorbates into condensed organic moieties and pores. Results of this work are critical for better understanding on the impact of minerals, bulk/surface polarity, and sorption domain arrangement of biochars on their efficacy for OPs removal and predicting the fate and risk of OPs.

Influence of Sustainable Biochars Produced from Kitchen Waste, Pig Manure, and Wood on Soil Erosion

The influence of biochars on water retention, mitigating nutrient leaching, and pollutant removal in green infrastructure has been explored in the past. However, there is a lack of understanding on how feedstock (i.e., biomass) would affect biochar physicochemical properties and hence, overall erosion control (including infiltration, surface, and sub-surface runoff) in green infrastructure. The main purpose of this study was to investigate the effect of biochars produced from three different feedstocks (pig manure, wood, and kitchen waste) on the erosion of granite residual soil. Flume experiments were conducted to measure and analyze soil erosion, runoff, and infiltration. The result showed that the runoff and soil erosion of kitchen waste biochar (KWB) samples were reduced by 17.7% and 21.7%, respectively. On the contrary, wood biochar (WB) and pig manure biochar (PMB) were found to enhance runoff and soil erosion. In addition, biochar particles were found in runoff and infiltration in erosion experiment. Thus, it is important to note that measures should be taken to prevent biochar loss when using biochar as a soil amendment. Additionally, the effects of different types of biochar on soil hydraulic and hydrophobicity properties should be taken into account as a selection criterion for choosing amendments in green infrastructure. This study finds that kitchen waste biochar has better performance in improving soil hydraulics and erosion.