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In the study, the layered double hydroxide (LDH) of NiZnFe and its composites with date-palm biochar (LDH-DPb) and carbon nanotubes (LDH-cnt) were synthesized for adsorbing reactive black 5 (RB5) dye from aqueous solutions. In the first 5 min, rapid adsorption was followed by a gradual increase in both dye uptake and removal efficiency of up to 60 min of starting time. In the investigated pH range (3.0–8.0), the removal efficiency linearly decreased while the sorption capacity linearly increased for all three adsorbents as their doses increased to 0.3 or 0.4 g following a decreasing trend up to 0.6 g. By increasing the initial RB5 concentration from 10 to 100 mg L−1, the removal efficiency linearly decreased. A nearly perfect fitting of the pseudo-second-order kinetic model to the adsorption data was observed; however, the Elovich kinetic model showed the heterogeneous surface of adsorbents with chemisorption. At the solid–liquid interface, from a thermodynamics point of view, we obtained the nonspontaneous nature of the adsorption of RB5 dye of the studied adsorbents with an increased disorder, which supported the endothermic nature onto the studied adsorption process. Furthermore, a nearly perfect fitting of the Langmuir model was obtained to the adsorption data, thereby suggesting the monolayer adsorption of RB5 dye onto the studied adsorbents. In the Dubinin–Radushkevich model, a good agreement of the calculated adsorption capacities to the experimental values were observed and the chemical adsorption of RB5 dye on to the studied adsorbents was proposed based on E (8 – 16 kJ mol−1).

Production of applicable and homogeneous biochar for soil amendment purposes would benefit from knowledge on how feedstock heterogeneity impacts key biochar pore properties and how the properties are transformed due to pyrolysis. This study aimed (1) to quantify how clonal differences and within-tree heterogeneity of a hybrid aspen feedstock (wood) impact biochar pore properties and (2) to estimate how pore properties of non-pyrolysed wood materials are transformed when pyrolysed into biochar. The study was conducted by collecting samples from a hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) clonal field trial. Key pore properties of non-pyrolysed and pyrolysed wood samples were quantified with 3D X-ray imaging and quantitative image analyses. The results demonstrated how pyrolysis shifted distinctively bi-modal pore size distributions of the wood samples towards smaller pore size regions. The bi-modal wood tissue structure controlled the pore structure also in the biochars. Due to decreasing cell wall thicknesses, the pyrolysis increased the porosity of the materials. While the thermal process homogenized differences in the wall thicknesses, the thicknesses of the feedstock were also shown to control the resulting thicknesses in the biochars. Mechanisms of biochar pore property formation can be considered important when designing applicable biochars for a chosen purpose. Clonal differences and within-tree heterogeneity had a direct impact only on the wall thicknesses and the pore diameters of vessels. These impacts can be of interest when planning feedstock utilization in biochar production. However, the results suggest that relatively homogeneous biochar can be produced from hybrid aspen feedstocks.

The adsorption removal of anti-inflammatory drugs from water by diverse materials has drawn great attention. This study investigated the adsorption of sulfamethoxazole (SMX) by two types of materials, UiO-66 and UiO-66-BC composites. Highly porous MOF composites with functional groups were synthesized by combining UiO-66 with corncob-based biochar at different molar ratios. SEM results showed that macroporosity of UiO-66-BC composites was increased by increasing the ratio of biochar. It was found that UiO-66-BC composites displayed highly improved adsorption performance of SMX relative to pristine UiO-66. UiO-66-BC (5%) had the highest SMX adsorption capacity, about 2.4 times those of pristine UiO-66. It was the high surface area of UiO-66 and redundant functional groups of biochar that increased the adsorption performance of composites. Moreover, UiO-66-BC can be reused and displayed the competitive adsorption efficiency after successive adsorption, which made it a potential adsorbent for the removal of SMX from water.

Wastewater sludge drying and incineration are conventional solids handling processes that are sometimes employed in water resource reclamation facilities. However, these two processes generate byproducts, sludge drying chaff and sludge incinerator ash, which are landfilled without taking advantage of their value. To gain value from these byproducts, a new synergistic catalytic pyrolysis process using chaff and ash was investigated in this study to improve energy production (i.e. generating a high yield pyrolysis gas) and generate useful products. Ash was used as a catalyst to decrease bio-oil that is corrosive and challenging for combustion in standard equipment, while increasing pyrolysis gas yield and energy for easier energy recovery. Ash increased the pyrolysis gas yield by 50% and product energy by nearly two-fold at the highest ash loading. The bio-oil volume was greatly reduced and contained fewer constituents based on GC-MS and GC-FID analyses. The product energy shifted from bio-oil to pyrolysis gas, which is relatively clean and easier for onsite energy recovery. Ca and Fe content in ash likely plays the catalytic role.

Chlordecone (Kepone) (CLD) is a highly persistent pesticide formerly used in the French West Indies. High levels of this pesticide may be found in soils and constitute a subsequent source of contamination for outdoor-reared animals due to involuntary ingestion of consistent amounts of soil. In that context, carbonaceous materials may be used to amend soil to efficiently decrease the bioavailability of such organic pollutants. The present study aims to assess the efficiency of diverse amendments of a contaminated Guadeloupe nitisol using two physiologically based approaches. A set of 5 carbonaceous materials (ORBO, DARCO, Coco CO2, Oak P1.5, Sargasso biochar) was tested and used to amend Nitisol at 2% (mass basis). Bioaccessibility assessment was performed using the Ti-PBET assay (n = 4). The relative bioavailability part involved 24 piglets randomly distributed into 6 experimental groups (n = 4). All groups were exposed during 10 days to a contaminated soil, amended or not with carbon-based matrices. A significant decrease in relative bioaccessibility and CLD concentrations in liver were observed for all amended groups in comparison to the control group, with the exception of the biochar amended soil in the bioaccessibility assay (p

As a kind of renewable resources with abundant reserves, research on the utilization of biochar has been paid more and more attention. However, the use of pomelo peel biomass carbon in the field of eletromagnetic wave absorption (EWA) has never been reported. In this study, the pomelo peel of natural recovery were carbonized at temperature of 700°C for 1 h in a high vacuum of 300 pa. The as-prepared biomass carbon were uniformly mixed with the paraffin by heat-assisted impregnation to prepare small ring-shaped devices, and the EWA characteristics of the small devices were investigated. The absorbing measurements were performed with the filling mass fraction of 30% and 50% of the biochar, respectively. The biochar with a mass fraction of 50% showed the excellent absorbing properties with the maximum reflection loss up to –44.3 dB at 9.84 GHz in the thickness of 2.0 mm, which is expected to be used as light, broadband and efficient EWA material.

Microbial fuel cells (MFCs) have gained remarkable attention as a novel wastewater treatment that simultaneously generates electricity. The low activity of the oxygen reduction reaction (ORR) remains one of the most critical bottlenecks limiting the development of MFCs. To date, although research on biochar as an electrocatalyst in MFCs has made tremendous progress, further improvements are needed to make it economically practical. Recently, biochars have been considered to be ORR electrocatalysts with developmental potential. In this review, the ORR mechanism and the essential requirements of ORR catalysts in MFC applications are introduced. Moreover, the focus is to highlight the material selection, properties, and preparation of biochar electrocatalysts, as well as the evaluation and measurement of biochar electrodes. Additionally, in order to provide comprehensive information on the specific applications of biochars in the field of MFCs, their applications as electrocatalysts, are then discussed in detail, including the uses of nitrogen-doped biochar and other heteroatom-doped biochars as electrocatalysts, poisoning tests for biochar catalysts, and the cost estimation of biochar catalysts. Finally, profound insights into the current challenges and clear directions for future perspectives and research are concluded.

The advanced oxidation process (AOPs) has caused great concern in recent years. Among them, biochar has been widely studied as a catalyst for advanced oxidation process because of its low price and low environmental risk. In this study, a novel ball milling assisted KOH activation biochar (MKBC) was prepared and applied in peroxydisulfate (PDS) activation to degrade tetracycline hydrochloride (TC-H). In comparison with the oxidation (3.48%) by PDS alone and adsorption (36.19%) by MKBC alone, the removal rate of TC-H was increased to 84.15% in the MKBC/PDS system, indicating that MKBC can successfully activate PDS. Besides, the catalytic activity of the MKBC to activate PDS for the degradation of TC-H is 58.33% higher than that of pristine biochar (PBC). In addition, MKBC has outstanding stability that after three repeated experiments, the removal rate of TC-H by the MKBC/PDS system still remains 77.35%. Meanwhile, the mechanism was investigated that the singlet oxygen (1O2) seized the principal position in the degradation of TC-H in the PDS/MKBC system. This study explored a novel, solvent-free and economic method to propose this extraordinary biochar, which provided a new strategy for the future research of biochar.

Attaining jointly high energy density at low cost is extremely challenging for lithium-sulfur (Li-S) batteries to compete with commercially available Li ion batteries (LIB). Here we report a class of bio-derived dense self-supporting cathode with ultralow porosity of 0.4 via self-densification effect during thermal drying without mechanical compression to realize a low-cost Li-S cell with high gravimetric/volumetric energy densities. Benefiting from the great preponderances of biochar, jointly high gravimetric/volumetric energy densities of 422 Wh kg−1/446 Wh L − 1 are achieved under conditions of high mass loading (6.5 mg cm−2) and extremely lean electrolyte (2.5 μL mg−1), the corresponding costs based on sub-Ah level pouch cell are estimated to be as low as $60/kWh-$90/kWh for the initial 20 cycles via a materials-to-system analysis, which is visibly less than that in the typical commercial LIB ($100/kWh). The current study presents meaningful opportunity to develop commercially viable Li-S batteries that are competitive on a specific energy/cost basis with current state-of-the-art LIB.

In this study, partially graphitic biochar was synthesized using peanut shell biomass and potassium ferrate (K2FeO4) with a simple strategy and applied for the removal of two commonly used nonstero...

Biofuels in the form of bio-oil and biochar have been produced by microwave heating of corn stover. Different adsorbents such as silicon carbide (SiC) and activated carbon (AC) with different ratios (10%, 20%, and 30%) to corn stover are investigated with the aims of enhancing the absorption of the microwave, maximizing the yields of the desirable products i.e. bio-oil followed by biochar as well as improving their qualities. Use of both the adsorbents improved the heating performance through increase in the maximal temperature and heating rate by 170 °C and 36 °C/min respectively compared to without adsorbent. Use of AC increased the yield of bio-oil up to 45 wt% while SiC increased the gas yields up to a maximum value of 48 wt%. The better physical properties such as 37%, 5.3, 2.9 mPa s, and 1 g/mL for water content, pH, viscosity and density respectively of bio-oil were obtained when using AC as an adsorbent. Also, use of AC helped in producing bio-oils which contained higher carbon and hydrogen contents as well as high calorific value (17 MJ/kg). Similarly, use of AC increased the contents of hydrocarbons and phenols in the bio-oil up to 36% and 28% respectively with low oxygen-containing compounds (2%). Also, use of AC produced the biochar having cleanest pores that were almost free of carbon-like impurities with a higher surface area of the pore (105.2 m2/g). In addition, biochar having low ash content, high carbon content, and calorific value (28 MJ/kg) were achieved. The net energy recovery with respect to raw corn stover was calculated to be of maximum value i.e., 55% when using AC. The AC and SiC were reused for further runs of the experiments (5 times) with few changes in the heating behavior and the yields of the pyrolytic products.

Waste recycling and reuse will result in significant material and energy savings. In this research, usage of hospital sludge as a biochar adsorbent for wastewater treatment plants was investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl2to increase surface area and porosity. A newly designed iron metal doped sludge biochar carbon (SBC) has effective adsorption of inorganic arsenic (As(III), As2O3) in water. The findings clearly demonstrate the viability and utility of using hospital sludge as a source of carbon to generate SBC. The adsorption mechanism of As(III) on SBC’s iron-metal-modified surface has been studied using density functional theory (DFT) to understand the impact of functional complexes on adsorption As(III). Tests showed physical as well as chemical adsorption of As(III) on Fe-SBC surface. Fe’s involvement in functional complexes greatly fostered SBC surface activity and it’s As(III) adsorption ability. The physical adsorption energies of As(III) with Fe functional complexes on the SBC surface were −42.3 KJ mol−1. Other hand, the chemical adsorption energies of As(III) on Fe-SBC surface was −325.5 KJ mol−1. As(III) is capable of interacting in a bidentate fashion with the dopants through the protonated oxygen atoms and this conformation of the cyclic structure is higher in the adsorption energy than the others.

Carbon-based materials (CBM), including activated carbon (AC), activated fibres (ACF), biochar (BC), nanotubes (CNT), carbon xenogels (CX) and graphene nanosheets (GNS), possess unique properties such as high surface area, sorption and catalytic characteristics, making them very versatile for many applications in environmental remediation. They are powerful redox mediators (RM) in anaerobic processes, accelerating the rates and extending the level of the reduction of pollutants and, consequently, affecting positively the global efficiency of their partial or total removal. The extraordinary conductive properties of CBM, and the possibility of tailoring their surface to address specific pollutants, make them promising as catalysts in the treatment of effluents containing diverse pollutants. CBM can be combined with magnetic nanoparticles (MNM) assembling catalytic and magnetic properties in a single composite (C@MNM), allowing their recovery and reuse after the treatment process. Furthermore, these composites have demonstrated extraordinary catalytic properties. Evaluation of the toxicological and environmental impact of direct and indirect exposure to nanomaterials is an important issue that must be considered when nanomaterials are applied. Though the chemical composition, size and physical characteristics may contribute to toxicological effects, the potential toxic impact of using CBM is not completely clear and is not always assessed. This review gives an overview of the current research on the application of CBM and C@MNM in bioremediation and on the possible environmental impact and toxicity.

Phosphate is a primary plant nutrient, serving integral role in environmental stability. Excessive phosphate in water causes eutrophication; hence, phosphate ions need to be harvested from soil nutrient levels and water and used efficiently. Fe-Mg (1:2) layered double hydroxides (LDH) were chemically co-precipitated and widely dispersed on a cheap, commercial Douglas fir biochar (695 m2/g surface area and 0.26 cm3/g pore volume) byproduct from syn gas production. This hybrid multiphase LDH dispersed on biochar (LDHBC) robustly adsorbed (~5h equilibrium) phosphate from aqueous solutions in exceptional sorption capacities and no pH dependence between pH 1–11. High phosphate Langmuir sorption capacities were found for both LDH (154 to 241 mg/g) and LDH-modified biochar (117 to 1589 mg/g). LDHBC was able to provide excellent sorption performance in the presence of nine competitive anion contaminants (CO32–, AsO43−, SeO42−, NO3–, Cr2O72−, Cl−, F−, SO42−, and MoO42−) and also upon remediating natural eutrophic water samples. Regeneration was demonstrated by stripping with aqueous 1 M NaOH. No dramatic performance drop was observed over 3 sorption-stripping cycles for low concentrations (5 ppm). The adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, TEM, and XPS. The primary sorption mechanism is ion-exchange from low to moderate concentrations (10–500 ppm). Chemisorption and stoichiometric phosphate compound formation were also considered at higher phosphate concentrations (>500 ppm) and at 40 °C. This work advances the state of the art for environmentally friendly phosphate reclamation. These phosphate-laden adsorbents also have potential to be used as a slow-release phosphate fertilizer.

Solar energy and biomass produce energy, which is sustainable and does not harm our environment. This characteristic of the two-energy feedstock is harnessed using the pyrolysis method to produce liquid and gaseous fuel that is transportable while bio-char regarded as a by-product has found usefulness in soil amendments. Solar-biomass pyrolysis technology combines these two low-density energy feedstock to produce high energy density fuel. The effectiveness of this process depends not only on the feedstock or reaction dynamics but also on the solar-thermal systems and reactor configuration. This review addressed the benefits of solar-biomass pyrolysis, available optical concentrating device, conceptual heating modes, the existing configuration of solar-thermal and reactor orientations, and some basic model equations applied in solar biomass pyrolysis.

Biochar is an excellent, but less-used candidate to serve as an alternative filler in poly(3-hydroxybutyrate) (PHB)-based composites. Increasing amounts of biochar between 20 and 50 wt% were incorporated in PHB/char and PHB/thermoplastic starch (TPS)/char composites and its effects on the microstructure, crystallization and thermal properties were investigated. PHB shows a significant reduction in molecular weight after processing and the increasing amounts of biochar decreases this even stronger. From thermogravimetric analysis, it was clear that the onset degradation temperature of the PHB/char composites (255 °C) is only slightly influenced by the biochar particles up to 40 wt%. Contrastingly, this temperature reduces to 245 °C when 50 wt% of biochar is added. Additional data confirm that morphology and crystallization kinetics are enhanced up to 40 wt% of biochar, while even higher percentages of filler clearly have an opposite effect. Finally, this work reveals the ability of TPS to work as an excellent intermediator between biochar and PHB at biochar concentrations up to 20 wt%, where degradation and resulting reduction in molecular weight remains limited as compared to that of the PHB/char sample. Furthermore, like biochar, TPS acts as a nucleation agent in the composites and removes the influence of the biochar on the thermal stability of the composites. This work was supported by Vlaams Agentschap Innoveren en Ondernemen (VLAIO) and European Institute of Innovation and Technology (EIT, BM20160604). This authors would like to acknowledge MartineVanhamel for DSC, FT-IR and TGA measurements.

Soybean residue (SR) is a main solid waste produced during the extraction of soybean oil with bulk volume. In addition to the use as vegetable protein feed, SR could also be used as feedstock for producing biofuels and carbon materials via pyrolysis. In this study, the pyrolysis behaviors of SR at varied temperatures and heating rates were investigated. The results show that the pyrolysis of the organic components in SR could reach completion even at 500 °C, due to the lower thermal stability of the organic component than that in the typical biomass. This also leads to the bio-oil with little heavy organics and also low carbon content of the resulting biochar, as the organic components decomposed to a significant extent while the charring reactions were insignificant. This leads to the biochar with low heating value and low energy yield when compared with that in the pyrolysis of typical biomass. In addition, the high content of proteins, amino acids and other nitrogen-containing nutrients make the SR derived bio-oil nitrogen-rich and a significant portion of nitrogen could also be retained in the biochar. These specialties have to be considered during their applications as either biofuels or functional carbon materials.

To explore the feasibility of converting oxy-fuel combustion flue gas into valuable syngas through char gasification process, the reactivity of three types of char (bituminous coal char, biochar, and waste char) were experimentally studied under atmospheric pressure in a fixed-bed reactor. The effects of flue gas flow rate and temperature, CO2/H2O/O2 ratio, char types on the char gasification characteristics were mainly investigated. It was found that when the flue gas temperature is 1200 °C or even higher, no matter which char is used, >90% CO2 conversion rate can be reached in line with the Boudouard equilibrium. The reactivity of biochar-H2O is relatively higher than that of waste char-H2O. Besides, 5% oxygen ratio in CO2/H2O mixture is preferred to promote the gasification reaction to some degree. It is important to balance the fixed carbon conversion rate and CO/H2 yield in syngas to decide the optimum residence time of char. Overall, it is a novel way of CO2 reduction and waste resources utilization.

A novel Egeria najas driven-biochar was activated by loading ferric chloride onto surface (FeCl3@EN-BC). The synthesized composite was evaluated for its physicochemical properties and Cr(VI) adsorption behavior and mechanism. The result of SEM showed that the modified biochar is less porous than raw Egeria najas biochar, but loaded with γ-Fe2O3 and Fe3O4 crystals. In addition, the results of FTIR, XRD and XPS also confirmed that Fe was successfully loaded on the Egeria najas biochar. Cr(VI) was efficiently removed by FeCl3@EN-BC within the pH range from 2.5–8.5. The thermodynamics parameters suggested that the adsorption processes of Cr(VI) were all spontaneous and endothermic. The overall removal mechanism was regarded as adsorption, surface complex formation, reduction and ion exchange reaction. Therefore, this modified biochar derived from Egeria najas has a potential of practical application in the removal of Cr(VI) from wastewater.

Presence of nutrients in municipal sewage water in high concentrations has raised awareness of their reuse as a vital limiting resource. With an aim to recover the nutrients in a form that can be used as a soil amendment, a novel biocompatible nanocomposite (BC-P@MNP) was fabricated using green methods. Polysaccharide induced biogenic magnetite nanoparticles (P@MNP) were immobilized onto the biochar of jackfruit peel (BC) to fabricate BC-P@MNP. Microwave irradiation employed during the fabrication of BC-P@MNP involved less energy consumption, high yields and better adsorption performance as compared to BC and other reported biochar-composites. Structural features like mesoporosity, crystallinity, magnetism, functionality and nano-sized dimension was demonstrated in BC-P@MNP. Under optimized conditions, batch studies revealed a maximum adsorption efficiency of 7.94 mg/g and 5.26 mg/g for phosphates and nitrates respectively. Thermodynamics revealed the feasibility and exothermicity of the system. The high selectivity in the presence of competing co-anions, high regeneration capacity and better separability enable BC-P@MNP to be used as advanced, economical adsorbent for wastewater applications. High nutrient recovery and biocompatibility ensured the potential of the spent adsorbent to be used as a soil amendment. Breakthrough curves obtained from fixed-bed column tests conducted on agricultural wastewater demonstrated the use of higher bed depths and lower flow rates for achieving higher phosphate removal as well as for ensuring lower unused column bed. The study demonstrated the technological advancement of a biogenic nanocomposite fabricated from green methods over other reported adsorbents for removal and recovery of nutrients from water.

Nowadays, iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water. In this study, boron-doped biochar (B-BC) was successfully prepared at various preparation conditions with the addition of boric acid. The as-prepared material has a more developed pore structure and a larger specific surface area (up to 897.97 m²/g). A series of characterization results shows that boric acid effectively activates biochar, and boron atoms are successfully doped on biochar. Compared with the ratio of raw materials, the pyrolysis temperature has a greater influence on the amount of boron doping. Based on Langmuir model, the maximum adsorption capacity of 800B-BC1:2 at 25 °C, 40 °C, 55 °C are 50.02 mg/g, 95.09 mg/g, 132.78 mg/g, respectively. Pseudo-second-order kinetic model can better describe the adsorption process, the adsorption process is mainly chemical adsorption. Chemical complexation, ions exchange, and co-precipitation may be the main mechanisms for Fe2+ removal.

Nickel sulfides are perfect anode materials for high-capacity and low-cost lithium-ion batteries (LIBs); however, with the shortcoming of polysulfide intermediate dissolution, volume expansion exceeding the limit during cycling also restricts their development. Herein, NiS/C composite materials are successfully anchored on chestnut shell fluff (CSF)-derived biochar by a glucose-auxiliary hydrothermal method along with an annealing treatment. The CSF biochar acts as an effective electron transmission channel for the rapid lithiation/delithiation of NiS and as a fixed sulfur carrier for inhibiting the dissolution of polysulfide. Glucose restrains the accumulation of NiS particles and then transforms into uniform amorphous carbon during annealing, which is more effective in buffering for rapid volume variation. Moreover, the CSF-NiS/C electrode exhibits a remarkable specific capacity of 1522.8 mAh g-1 (0.1 A g-1) and distinguished rate performance with 295 mAh g-1 capacity (3 A g-1), which are better than those of the pure NiS/C anode material displays. Researchers may be inspired by both of these reasonable design and synthesis strategies that are beneficial for the development of high-performance nickel-based sulfide anode materials for LIBs.

To understand the catalytic upgrading of bio-oil over char-based catalyst, pyrolysis of pine sawdust with various char catalysts under different reaction temperatures was performed in a fixed-bed reactor, from which the liquid product was analyzed with gas chromatography-mass spectrometry (GC/MS). The main pyrolytic liquids were ketones and acids in the non-catalytic pyrolysis run, which were mainly derived from the pyrolysis of cellulose and hemicellulose in biomass by ring opening and side chain cracking reactions, while the relative content of phenolic substances obtained from catalytic reaction at 400 °C over CO2-activated char increased from 33.79% to 78.12% with the increasing char activation time from 0.5 to 2.0 h, resulting from the formation of more multiple active sites (including surface active groups and the pore characteristics) on activated char. When the catalytic reaction temperature reached 600 °C, the quality of the bio-oil was further improved since the relative content of aromatic hydrocarbons increased from 7.30% to 21.04% at the expense of elimination of some oxygen-containing compounds (e.g., ketones, acids, aldehydes, etc). Furthermore, the content of phenol in phenolic compounds increased from 26–64% to 51–97%.

Watermelon peel residues were used to produce a new biochar by dehydration method. The new biochar has undergone two methods of chemical modification and the effect of this chemical modification on its ability to adsorb Cr(VI) ions from aqueous solution has been investigated. Three biochars, Melon-B, Melon-BO-NH2 and Melon-BO-TETA, were made from watermelon peel via dehydration with 50% sulfuric acid to give Melon-B followed by oxidation with ozone and amination using ammonium hydroxide to give Melon-BO-NH2 or Triethylenetetramine (TETA) to give Melon-BO-TETA. The prepared biochars were characterized by BET, BJH, SEM, FT-IR, TGA, DSC and EDAX analyses. The highest removal percentage of Cr(VI) ions was 69% for Melon-B, 98% for Melon-BO-NH2 and 99% for Melon-BO-TETA biochars of 100 mg·L−1 Cr(VI) ions initial concentration and 1.0 g·L−1 adsorbents dose. The unmodified biochar (Melon-B) and modified biochars (Melon-BO-NH2 and Melon-BO-TETA) had maximum adsorption capacities (Qm) of 72.46, 123.46, and 333.33 mg·g−1, respectively. The amination of biochar reduced the pore size of modified biochar, whereas the surface area was enhanced. The obtained data of isotherm models were tested using different error function equations. The Freundlich, Tempkin and Langmuir isotherm models were best fitted to the experimental data of Melon-B, Melon-BO-NH2 and Melon-BO-TETA, respectively. The adsorption rate was primarily controlled by pseudo-second–order rate model. Conclusively, the functional groups interactions are important for adsorption mechanisms and expected to control the adsorption process. The adsorption for the Melon-B, Melon-BO-NH2 and Melon-BO-TETA could be explained for acid–base interaction and hydrogen bonding interaction.

In this study, the pyrolysis of flaxseed residue (FSR), a solid waste in the production of flaxseed oil, was carried out, aiming to understand the characteristics of the pyrolysis products. Comparing with traditional biomass (such as poplar wood), the organic components in FSR are easier to be cracked, producing the bio-oil with little heavy components. The high content of proteins in FSR made the resulting bio-oil nitrogen-rich. The resulting biochar contained abundant nitrogen, as some of the N-containing organics were thermally stable even at 650 °C. The significant cracking reactions made the biochar with the relatively lower carbon content, heating value and energy yield than that from biomass. The changes of functionalities of the biochar versus increasing temperature were also characterized with in situ diffuse reflectance infrared fourier transforms spectroscopy technique. The transformation of the carbonyl and other functionalities on surface of the biochar was sensitive to the change of temperature and the increase of temperature promoted the deoxygenation and aromatization reactions.

Biochar (BC) has exhibited a great potential to remove water contaminants due to its wide availability of raw materials, high surface area, developed pore structure, and low cost. However, the application of BC for water remediation has many limitations. Driven by the intense desire of overcoming unfavorable factors, a growing number of researchers have carried out to produce BC-based composite materials, which not only improved the physicochemical properties of BC, but also obtained a new composite material which combined the advantages of BC and other materials. This article reviewed previous researches on BC and BC-based composite materials, and discussed in terms of the preparation methods, the physicochemical properties, the performance of contaminant removal, and underlying adsorption mechanisms. Then the recent research progress in the removal of inorganic and organic contaminants by BC and BC-based materials was also systematically reviewed. Although BC-based composite materials have shown high performance in inorganic or organic pollutants removal, the potential risks (such as stability and biological toxicity) still need to be noticed and further study. At the end of this review, future prospects for the synthesis and application of BC and BC-based materials were proposed. This review will help the new researchers systematically understand the research progress of BC and BC-based composite materials in environmental remediation.

Here adsorption studies were proposed on a carboxylated sludge biochar (CSB) material modified by HNO3 to assess its capacity in the removal of cobalt from aqueous solution. The as-prepared sludge biochar material was characterized by Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The isotherm process could be well described by the Langmuir isotherm model. The adsorption kinetics indicated that cobalt adsorption followed a pseudo-second-order kinetics model. The mechanism between Co(II) and biochar involved electrostatic interaction, ion exchange, surface complexation and physical function. The adsorption capacity on CSB was as high as 72.27 mg·g−1, surpassing original sludge biochar (SB) as CSB had abundant oxygen-containing functional groups and many hydroxyls, plus the BET surface areas increased when SB was modified by HNO3, which stimulated adsorption effect. Therefore, this work shows that CSB could be used as an efficient adsorbent to remove Co(II) in wastewater. Highlights The material has abundant oxygen-containing functional groups, which are beneficial for binding Co(II).; The isotherm process could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model.; The adsorbent has an efficient adsorption capacity for Co(II), as high as 72.27 mg·g−1.

Development of lignin-derived carbon adsorbents with ultrahigh phosphate adsorption activity and rapid adsorption kinetics is of great importance, yet limited success has been achieved. Herein, we develop a CeO2 functionalized N-doped lignin-derived biochar (Ce@NLC) via a cooperative modification strategy for effective and fast phosphate capture. The novel modification strategy not only contributes greatly to the loading of well-dispersed CeO2 nanoparticles with a smaller size, but also significantly increases the relative concentration of Ce(III) species on Ce@NLC. Consequently, an enhanced capture capacity for phosphate (196.85 mg g−1) as well as extremely rapid adsorption kinetics were achieved in a wide operating pH range (2–10). Interestingly, Ce@NLC exhibited a strong phosphate adsorption activity at even low-concentration phosphorus-containing water. The removal efficiency and final P concentration reached 99.87% and 2.59 μg P L−1 within 1 min at the phosphate concentration of 2 mg P L−1. Experiments and characterization indicated that Ce(III) species plays a predominant role for the phosphate capture, and ligand exchange, together with electrostatic attraction, are the main adsorption mechanism. This work develops not only an efficient carbon-based adsorbent for phosphate capture, but also promotes the high-value application of industrial lignin.

With the increased awareness of reusing solid wastes for higher sustainability and the concern of water pollution associated with phosphorus over-emission, there are strong interests in developing solid waste based adsorbents for purifying phosphorus-containing wastewater. As a rich calcium resource, paper mill sludge (i.e., a major solid waste from pulping industry) can be used as phosphorus removal adsorbent after calcination. Thus, in this work, a simple and clean thermally treating route has been proposed for preparing calcium-containing biochar from paper mill sludge. The effect of the physicochemical properties of paper mill sludge and its carbonization condition on phosphorus adsorption has been analyzed. Moreover, the influence of some key adsorption parameters, e.g., biochar dosage, initial pH of solution, co-existing anions, initial phosphorus concentration and contact time has also been investigated. The results showed that the phosphorus adsorption data could be fitted well with pseudo-second-order kinetic and Langmuir isothermal models. The calculated maximum adsorption capacity of the as-prepared optimal calcium-containing biochar could reach to 68.49 mg·g−1 at 25 °C. Combined with the characterization results, it can be reasonably inferred that the adsorption process was chemisorption-dominated. Lastly, the application of this spent adsorbent in agriculture field has also been discussed. In brief, this work provided a feasible strategy for converting paper mill solid waste to an environmental functional material (i.e., calcium-rich biochar) for remediation of eutrophic water.

Waste chicken feathers are the ideal precursor for the production of low-cost N-enriched biochar. KOH-modified N-enriched biochar (KNB) containing 15.92 wt% N was successfully prepared using waste chicken feathers. The adsorption kinetics results showed that KNB had rapid Cd (2 h) and Pb (1 h) adsorption rates. The Cd and Pb adsorption capacities of KNB (the values of KF were 22.324 (Cd) and 119.654 (Pb) mg1−(1/n)·L1/n·g−1) were 7.07 and 26.52 times higher than those of the original biochar based on the adsorption isotherm results. The KNB was stable at pH 3–6 and had stronger co-adsorption capacities in double-ion systems. Based on the adsorption experiments and various characterization methods, we concluded that the primary Cd and Pb adsorption mechanisms of KNB involved electrostatic interactions, cation-π interactions, complexation, and K+ exchange. The precipitation mechanism could partially account for Pb adsorption but not for Cd adsorption. KOH modification enhanced the electronegativity of biochar and then increased the electrostatic attraction. Surface O- and N-containing functional groups were involved in Cd and Pb adsorption. Graphitic-N, oxidised-N, and O C O were the main active adsorption groups, the relative contents of which increased after KOH modification, thus increasing the Cd and Pb adsorption performance. Therefore, KNB can be used as a fast and highly efficient adsorption agent to remove Cd and Pb from wastewater containing either Cd and Pb or a combination of these two metals.

In this study, the influence of saw dust based biochar on the removal of heavy metal ions contaminants in gold tailings wastewater was investigated. The target pollutants were cyanide (CN−), chromium (Cr3+), iron (Fe3+), zinc (Zn2+), nickel (Ni2+), lead (Pb2+), manganese (Mn2+) and copper (Cu2+). Their composition was determined before and after the adsorption process using biochar. The biochar loading was varied between 10 mg/L, 30 mg/L and 50 mg/L and the retention times between 2 and 12 h in a fixed bed column. The Pearson Coefficient analysis method indicated that the utilization of biochar significantly decreased heavy metal ions contaminants by more than 70% and there was a strong negative relationship between retention time and concentration of remaining metal ions at 95% confidence interval. Negative coefficients for effect of biochar loading and ions concentrations for CN−, Cr3+, Fe3+, Zn2+, Ni2+, Pb2+, Mn2+ and Cu2+ ions of 0.76, 0.74, 0.75, 0.83, 0.85, 0.87 and 0.87 respectively were observed. The magnitude of each coefficient indicated a significant reduction in the heavy metal ion. Saw dust based biochar can be successfully used to reduce heavy metal contaminants in tailings wastewater. However, more retention time and higher biochar loadings should be adopted to meet for the WHO disposal guidelines of CN−, Ni2+ and Pb2+..

Black soldier fly (BSF) larval bioconversion can recycle nutrients in organic wastes into larval biomass and frass. While the frass has been commonly marketed as a soil amendment, its usefulness in soilless cultivation remains largely unexplored. Growth experiments were conducted to investigate the effectiveness of surplus food-derived and okara-derived BSF larval frass as an incorporated compost, side-dress fertilizer and frass-tea drench for the cultivation of pak choi and lettuce in waste-wood derived biochar growing media. Pak choi yields from treatments with surplus food-derived frass and biochar at a 10:90 (v/v) ratio and inorganic fertilizer were comparable to those of the control which consisted of soil, peat-based compost and inorganic fertilizer. However, yields decreased with increasing frass incorporation rates owing to high salinity and potentially low oxygen conditions in the growing media. When used as a fertilizer on biochar-coir growing media, the direct application of frass as a side-dress fertilizer was 1.6-6.8 times more effective in promoting lettuce growth than the application as a frass-tea drench. Frass fertilizers derived from surplus food outperformed those derived from okara by 1.3-5.3 times. Lettuce yields were not significantly different between the treatment with surplus food-derived frass applied as a side-dress fertilizer and the control of liquid inorganic fertilizer. Variations in fertilizing potential were attributed to nutrient availability and the presence of plant growth promoting microbes in the growing media. BSF larval frass derived from food waste shows promise in partially replacing unsustainable agricultural inputs for leafy vegetable cultivation, including soil and inorganic fertilizers.

Biochar supported nickel (Ni/BC) has been widely studied as a cheap and easy-to-prepare catalyst with potential applications in tar reforming during the gasification of low-rank fuels, such as brown coal and biomass. However, the role and behaviors of inherent K species, especially their interactions with Ni particles and the biochar support, are not well understood yet. In this work, three Ni/BC catalysts with varying K amount were prepared from raw, water-washed, and acid-washed biomass. They were used in steam reforming of toluene as a tar model compound to elucidate the effects of inherent K on the catalytic activity and stability. Detailed characterization indicated that K enhanced water adsorption due to its hydroscopicity and lowered the condensation and graphitization degrees of biochar, but the alteration to the electronic state of Ni was not observed. These effects together led to a temperature-dependent role of K. That is, at relatively low temperatures of 450 and 500 °C, toluene conversion was increased in the presence of K, due to the increased concentration of adsorbed water around Ni particles. By contrast, at relatively higher temperatures of 550 and 600 °C, although initial high activity was achieved, Ni/BC with K deactivated rapidly because of the accelerated consumption of the biochar support.

Depletion of fossil fuels resulted in the search for alternative energy sources that are eco-friendly and renewable. Biodiesel had become one of the promising alternative energy sources in the past decade. The conventional biodiesel production cost is very expensive on an industrial scale and becomes the main challenge. To reduce the production cost, the catalyst is considered a promising tool for speeding the biodiesel production rate. In this aspect, many types of research have been conducted by utilizing catalysts produced from various feedstocks for biodiesel production and purification. Recently, biochar was used as a catalyst for biodiesel production. Henceforth, the present review comprises an overview of biochar feedstock, production of biochar via pyrolysis, activation of biochar and process conditions for biochar. Apart from the production of biochar, the main focus of this review is on the biochar-based catalyst for biodiesel production. This biochar-based catalyst will act as a sustainable source of energy by reducing the economy of biodiesel production.

In this study, the use of magnetic biochar particles recovered from biorefinery by-products (humins) for adsorption of hydrophilic organic pollutants was investigated. The biochar was prepared by thermal treatment of crude humins followed by a grinding step after which a magnetic iron oxide was co-precipitated on the biochar surface. The resulting iron oxide content of the biochar composite was found to be 9% by volume, and the presence of a characteristic Fe–O vibrational band was observed by FTIR-ATR. XPS analysis of Fe2p spectrum enabled the nature of iron oxide to be identified as maghemite. Finally, magnetometry measurements demonstrated the superparamagnetic properties of maghemite. The adsorption of methylene blue on the biochar composite was found to be fast (less than 1 h at pH 6 with an initial concentration of methylene blue of 2 × 10–5 mol L−1). Kinetics data were satisfactorily modelled by both first and second order models. Freundlich and Langmuir models were applied to adsorption isotherms data. Maximum adsorption capacity (3.35 × 10–5 mol g−1), and Langmuir and Freundlich constants (2.33 × 104 L mol−1 and 5.70 × 10–5 mol0.913 L0.087 g−1 respectively) were found to be comparable to the average of those found in the literature. Electrostatic attraction between oppositely charged methylene blue and magnetic biochar was presumed to be the dominant interaction governing adsorption at environmental pH values. Lastly, a laboratory-scale experimental device with magnetic filtration under flow allowed the complete separation of the magnetic biochar composite from the liquid phase. This study shows that this magnetic biochar composite is a promising and economically interesting recovery route for biorefinery by-products and could be used for adsorption purposes.

Biochar application and enhanced weathering are negative emission technologies (NETs) with the potential for large-scale deployment for the removal of CO2 from the atmosphere. Biochar is a solid product of pyrolysis that can permanently store carbon when applied in soil due to its chemical recalcitrance. Enhanced weathering is based on the acceleration of the natural reaction of moisture, CO2, and alkaline minerals. Both of these NETs rely on the application of pulverized material to different types of terrestrial sinks, which can include marginal and agricultural land. These two NETs can be used separately or concurrently, depending on local sink conditions. In some cases, simultaneous application of biochar and mineral powder to soil has the advantage of attaining additional beneficial effects of soil amendment. Although recent papers have reported the development of process integration models for optimizing carbon management networks based on either biochar application or enhanced weathering, none have reported models integrating these two NETs in the same system. To address this gap, a fuzzy mixed-integer linear programming model is developed that integrates biochar application and enhanced weathering for large-scale carbon sequestration. Fuzzy set theory provides a well-tested framework for integration of both subjectivity and uncertainty into mathematical programming. The model determines the optimal allocation of biochar and/or alkaline minerals from each source to each sink, while considering the application limits and CO2 sequestration potential. An illustrative case study is solved that clearly demonstrates the application of the model. The case study shows interesting results that can guide how the full sustainable potential of these two technologies can be utilized in a carbon management network.

Biological porous carbon (BPC) is an easily available and environmentally friendly matrix for the preparation of shape-stabilized phase-change materials (ss-PCMs). However, BPC-based ss-PCMs have the problems of low thermal conductivity and poor loading capacity. In this study, we found that cabbage mustard biochar (CMB) used as the supporter of tetradecanoic acid (TA) to fabricate the ss-PCM of TA/CMB could dramatically enhance the thermal conductivity of ss-PCM, which could reach 0.597 ± 0.024 W/(m·K) and was higher than the values of almost all ss-PCMs based on biochar. The loading capacity of TA in TA/CMB could reach 57.07%, and a high phase change enthalpy of 103.55 ± 2.65 Jg−1 was obtained. More importantly, the CMB could be derived from the agricultural waste of cabbage mustards, which is easily available. Hence, the developed TA/CMB with outstanding performances and inexpensive price in this study can be employed as an energy storage material in practical applications.

Widely reports have evaluated the use of biochar (BC) composites to layered double hydroxide (LDH) to adsorb dyes from wastewater. However, its applicability for adsorbing a mixture of cationic dyes such as Malachite green (MG), Rodhamine-B (Rh-B), and Methylene blue (MB), which causes carcinogenic and mutagenic effects on aquatic life, has not been studied. In this work, we compared the performance of CaAl-LDH/BC adsorbent with or without the addition of BC in the adsorption of cationic dyes. The adsorption study was prepared in a batch system using various temperatures, concentrations, and also contact time. The results of the characterization of Ca/Al-Biochar composite showed the unique diffraction of XRD pattern, and also showed two characteristics of starting materials. Surface area analysis by BET method showed Ca/Al-Biochar composite has a higher surface area than starting material. The results of the adsorption study of MG showed that Ca/Al-Biochar follows the pseudo-second-order kinetic model. The adsorption capacity of MG on Ca/Al-Biochar was up to 71.429 mg/g and shows selectivity toward MG in an aqueous solution. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

A novel green composite catalyst was prepared by doping CuFe2O4 nanoparticles in the malt bagasse biochar. Composites with different ratios of malt biochar and CuFe2O4 were produced and characterized by XRD, FE-SEM, EDS, HR-TEM, UV–vis, and Zeta potential. The results revealed that CuFe2O4 was successfully supported on the malt biochar surface. The prepared composites showed the band gap energies were narrower than of CuFe2O4, increasing the photocatalytic activity. At 60 min of heterogeneous photo-Fenton, tests under visible light indicated CuFe2O4 removed 39 % of the rhodamine B color, while composites CFO1B3, CFO1B1, and CFO3B1 removed 88 %, 81 %, and 44 % of the dye, respectively. The recycling of the CFO1B3 composite indicated that it can be used in eight cycles without major losses in efficiency. In sunlight, the CFO1B3 composite achieved efficiencies of 100 % for 10 mg L−1 and 50 mg L−1 of rhodamine B at 10 and 20 min of reaction, respectively. In the proposed mechanism, it was verified that the radical OH, O2 − and h+ were the predominant reactive species involved in the degradation to intermediates of low m/z. Results showed that the novel composite formed is a promising photocatalyst for removing organic pollutants in water.

The ever-detrimental condition of the environment due to the fossil fuel utilization has catalyzed the development of biodiesel. Biodiesel is produced mainly via transesterification and the entire process comprises of several major components; the feedstock, the catalyst, the reaction, and the product separation or purification. There are various factors affecting the amount and quality of biodiesel produced, such as the type and amount of feedstock and catalyst, alcohol-to-feedstock ratio, and reaction temperature and time. The performance of biodiesel reactors in providing energy and time efficient biodiesel production is also among the subject of recent studies. To produce biodiesel commercially and efficiently, it is important to recognize the novel technologies that are promising for biodiesel production. With this in mind, this article presents a review of the recent advancement and classification of the feedstock, the catalyst for biodiesel production, and the biodiesel production reactor. Furthermore, this article also highlights the development and application of oil extraction techniques, biochar as a biodiesel catalyst, and the magnetic biodiesel catalyst. The biodiesel production reactor and parameters optimization are also discussed in this article in order to provide a better context on the chemical reaction.

Paddy soil and irrigation water are commonly contaminated with hexavalent chromium [Cr(VI)] near urban industrial areas, thereby threatening the safety of agricultural products and human health. In this study, we develop a porous and high specific area bone char (BC) to support nanoscale zero-valent iron (nZVI) and apply it to remediate Cr(VI) pollution in water and paddy soil under anaerobic conditions. The batch experiments reveal that BC/nZVI exhibits a higher removal capacity of 516.7 mg/(g•nZVI) for Cr(VI) than nZVI when normalized to the actual nZVI content, which is 2.8 times that of nZVI; moreover, the highest nZVI utilization is the nZVI loading of 15% (BC/nZVI15). The Cr(VI) removal efficiency of BC/nZVI15 decreases with increasing pH (4 – 10). Coexisting ions (phosphate and carbonate) and humic acid can inhibit the removal of Cr(VI) with BC/nZVI15. Additionally, BC exhibits a strong advantage in promoting Cr(VI) removal by nZVI compared to the widely used biochar and activated carbon. Our results demonstrate that reduction and coprecipitation are the dominant Cr(VI) removal mechanisms. Furthermore, BC/nZVI15 shows a significantly higher reduction and removal efficiency as well as a strong anti-interference ability for Cr(VI) in paddy soil, as compared to nZVI. These findings provide a new effective material for remediating Cr(VI) pollution from water and soil.

Lignocellulosic biomass has attracted great interest in recent years for energy production due to its renewability and carbon–neutral nature. There are various ways to convert lignocellulose to gaseous, liquid and solid fuels via thermochemical, chemical or biological approaches. Typical biomass derived fuels include syngas, bio-gas, bio-oil, bioethanol and biochar, all of which could be used as fuels for furnace, engine, turbine or fuel cells. Direct biomass fuel cells mediated by various electron carriers provide a new direction of lignocellulose conversion. Various metal and non-metal based carriers have been screened for mediating the electron transfer from biomass to oxygen thus generating electricity. The power density of direct biomass fuel cells can be over 100 mW cm−2, which shows promise for practical applications. Lignocellulose and its isolated components, primarily cellulose and lignin, have also been paid considerable attention as sustainable carbonaceous materials for preparation of electrodes for supercapacitors, lithium-ion batteries and lithium-sulfur batteries. In this paper, we have provided a state-of-the-art review on the research progress of lignocellulosic biomass as feedstock and materials for power generation and energy storage focusing on the chemistry aspects of the processes. It was recommended that process integration should be performed to reduce the cost for thermochemical and biological conversion of lignocellulose to biofuels, while efforts should be made to increase efficiency and improve the properties for biomass fuelled fuel cells and biomass derived electrodes for energy storage.

This study investigates feasibility in the technical convergence of cold plasma and Fe-impregnated biochar to remove slowly-biodegradable methylene blue (MB) as a model contaminant. A problematic biowastes, spent coffee ground, was reused as a renewable source of biochar, and it impregnates Fe to enhance adsorption performance. Results verify that the cold plasma’s advanced oxidation coupled with the biochar increases overall MB removal efficiency and accelerates degradation kinetics. Experimental data regression verifies that the impregnated Fe significantly enhances the kinetic constants for total organic carbon (0.019–0.045 min−1) and MB (0.050–0.065 min−1). Also, it was confirmed that Fe-impregnation clearly shortens the periods required for almost complete MB degradation to within 1 h. In addition, the higher Fe was impregnated, the stronger synergistic effects on MB degradation rates was observed. The analyses of nitrate, nitrite, and sulfate supports that the MB could be lower down to detection limit by the suggested combination. These results provide useful information about the synergistic combination of physicochemical processes as a viable option to effectively manage slowly-biodegradable pollutants.

Agroforestry biomass involving cedar wood (CW), polar wood (PW), corn stalk (CS) and wheat straw (WS) was torrefied in a fixed-bed reactor under the torrefaction temperature (T) of 200–300 °C and the holding time (τ) of 10–60 min to prepared straw biochars (WSC, CSC) and woody biochars (PWC and CWC). The effects of biomass species, torrefaction temperature and holding time on the hygroscopicity of biochars were investigated under constant temperature and humidity. Combined with the results of N2 adsorption/desorption and FTIR of raw biomass and its biochars, the mechanism of torrefaction conditions on the hygroscopicity of biochar was discussed. The obtained results indicated that water absorption process of biochar can be divided into two stages of initial rapid water absorption and the later slow water absorption. The equilibrium moisture content (EMC) decreases, the hygroscopicity reduction extent (HRE) increases gradually, and hydrophobicity of biochar is enhanced with increasing torrefaction temperature. However, too high torrefaction temperatures (T ≥ 275 °C) has little or even adverse effect on the hydrophobicity of biochars. The longer holding time has a certain influence on the hydrophobicity of biochar, but the overall effect is not significant. The hydrophobicity of woody biochars (PWC and CWC) is better than that of straw biochars (WSC and CSC) at the same torrefaction conditions. The severe torrefaction of T ≥ 275 °C and τ ≥ 40 min are able to improve the hydrophobicity of woody biochars, however it has negative effect on straw biochars. The hydrophobicity of four biochars is ordered as PW > CW > WS ≈ CS at the same torrefaction conditions. The water adsorption mechanism of biochars is influenced by the coupling effects of physical structure evolution, release of hydrophilic oxygen-containing functional groups and pyrolytic tar condensation, and the severer the torrefaction, the more significant the influence is.

Objectives: Among various radioactive contaminants, radioactive cesium is one of the most harmful radionuclides that causes human health issues due to its high emission of gamma-ray, high solubility, high mobility, high fission yield, and long half-life. Different kinds of adsorbents have been developed for the removal of cesium from radioactive wastewater. Especially, biochar has attracted great attention as a potential adsorbent in the treatment of pollutants and for water purification. In addition, Prussian blue is a cubic lattice structure that contains a cage size similar to the hydrated cesium ionic radius, indicating it can selectively remove cesium ions. Therefore, the aim of this study is to investigate the cesium adsorption performance of synthesized Prussian blue-immobilized coffee ground biochar (PB-CGBC) under various experimental conditions for cesium removal from radioactive wastewater.Methods: After wasted coffee ground was washed and dried, it was heated at 400℃ with 10℃/min of heating rate and 5 h of retention time in a furnace with little or no available air. The PB-CGBC was synthesized using a facile co-precipitation method. Fourier transform-infrared spectroscopy, X-ray diffractometer, field emission-transmission electron microscope, Brunauer-Emmett-Teller, and zeta potential analyzer were used to analyze physico-chemical characteristics and surface structure of the synthesized adsorbents. The kinetic and equilibrium experiments of cesium adsorption on PB-CGBC were carried out and the effect of pH, temperature, initial cesium concentration, and contact time were also investigated in a batch system.Results and Discussion: The characteristic analysis clearly confirmed the successful synthesis of PB-CGBC, indicating its abundant functional groups and special surface structure. In the batch study, it was found that the cesium adsorption onto the PB-CGBC was exothermic nature. The Elovich kinetic model and Temkin isotherm also provided a good correlation with the cesium adsorption reaction onto the PB-CGBC. The maximum adsorption capacity of PB-CGBC for cesium was 129.57 mg/g at 15℃ and pH 8 at 40 mM of an initial cesium concentration, which was one of the highest values among those of previously reported adsorbents.Conclusions: In this study, the PB-CGBC was synthesized by immobilizing Prussian blue to the surface of coffee ground biochar and successfully applied for the adsorptive removal of cesium ions. Based on the experimental results, the synthesized PB-CGBC can be served as a great adsorbent for treatment of wastewater polluted with radioactive cesium.

Creation of oxygen-containing functional groups on the biochar surface can highly improve its hydrophilicity and amend its behaviour in aquatic systems. Hydrogen peroxide, ozone, potassium permanganate and nitrogen acid were most usually used reagents for the surface oxidation. On the contrary, biochar activation by strong acids can be a costly process at the industrial scale and can raise environmental problems due to the disposal of activated carbon. Hence, there is a need to search for cheaper and cleaner products for the modification of biochar. For this reason, weak acids, such as solution of rhamnolipids or rainfall water solution, can be used. In this study, it was found that lower size biochar particles had higher wettability compared to larger size particles, since it was categorized as slightly hydrophobic (2.67 s). Steam of average concentration of rhamnolipid solution (20 mg/l) had the highest effect on the enhancement of biochar surface area (15.2 m2/g) and satisfactory impact on the reduction of initial hydrophobicity (4210 s). Biochar modified with increased concentration of nitric acid solution (from 65 to 20%) wettability was in accordance with the increase of surface area (from 4210 to 3907 s and from 1.27 to 4.36 m2/g).

Imidazolinones are a group of herbicides with high potential of leaching and long half-lives that are posing a threat to water resources’ quality especially in tropical areas. Biochar, a carbon-rich bio-sorbent, has shown its ability to stabilise organic substances in soils and therefore, potentially is able to reduce their leaching. Biochar is a sustainable and cost-effective material which can be produced from locally available wastes. This work, for the first time, evaluated the biochar’s effects on leaching of two polar members of imidazolinones family namely imazapic and imazapyr, and also Onduty® which is a mixture of these two herbicides, in heavy soil of tropical paddy fields. Leaching columns accompanied with artificial irrigation were used during the laboratory experiment. The herbicides were extracted from both collected leachates and soil columns. Soil amendment with designed biochars significantly reduced the herbicides’ leaching percentages. Oil palm empty fruit bunch (OPEFB) and rice husk (RH) were used as pyrolysis feedstock. About 16% of the applied imazapic was leached out from biochar-free soil. For RH and OPEFB biochar-amended soils, the amounts were 4.3% and 3.6%, respectively. The highest percentage of imazapyr leached out from non-amended soil was (14.2%) followed by RH (4.0%) and OPEFB (2.8%) in biochar-amended soils. Also, 15.2% of the applied Onduty® was leached from non-amended soil. Adding RH and OPEFB biochars could reduce the herbicide leaching to 4.2% and 3.0%, respectively. Soil amended with biochars retained the higher percentages of the herbicides in top 7.5 cm depths. The media sorption capacities were negatively correlated to the amounts of herbicides leached out from soils but positively to the amounts of the herbicides remaining in the soil. Total amount of herbicides adsorbed by biochars-amended soils was more than 95%. Cation/water bridging ion exchange, ligand exchange, electrostatic attraction, and hydrophobic partitioning are the main ways imidazolinones can be adsorbed to soil. It was concluded that biochar application has the potential to reduce polar imidazolinones’ leaching and their environmental pollution. The custom-engineered biochars can specifically control the pesticides transfer and then can certainly enhance the biochars’ commercial values for their applications in the environment.