KOH-activated Biochar Research Articles

Circular economy approach: Nutrient recovery and economical struvite production from wastewater sources by using modified biochars

The enrichment of phosphorus (P) and nitrogen (N) in aquatic systems can cause eutrophication. Moreover, P rocks may become exhausted in the next 100 years. A slow-release fertilizer called struvite (MgNH4PO4.6H2O) can reduce surface runoff. However, the high cost of raw material or chemicals is a bottleneck in their economical production. Therefore, incinerated sewage sludge ash, food wastewater, and bittern were combined as the sources of P, N, and Mg, respectively. Sawdust biochar was used to enhance the adsorptive recovery of nutrients. First, recovery kinetics was studied by comparing bittern-impregnated biochar (BtB) with the Mg-impregnated biochar (MgB). Subsequently, the synergistic physical and chemical interactions were observed for P and N recovery. Almost complete PO43–P recoveries were achieved within 10 min for both biochars. However, NH4+-N recovery was stable after 2 h, with 26% recovery by MgB and 20% recovery by BtB. Biochars activated with steam (steam-activated biochar) and KOH (KOH-activated biochar) gave superior activities to those of unactivated biochars and activated carbon (AC) nutrient recovery and struvite purity. Moreover, the activated biochars showed a lower risk of surface runoff, similar to that of AC. Therefore, activated biochars can be used as an alternative to AC for economical struvite production from a combination of wastewater sources.

Synthesis of Activated Biochar from the Bark of Moringa oleifera for Adsorption of the Drug Metronidazole Present in Aqueous Medium

Moringa oleifera seeds, in particular, have been used for water and wastewater treatment due to their ability to remove many pollutants. Therefore, the present work aims to produce bioadsorbent materials by pyrolysis using biomass from the seed shell of Moringa oleifera to remove the drug Metronidazole present in an aqueous medium. The biochars produced were activated with phosphoric acid (H3PO4) and potassium hydroxide (KOH) to compare the material’s modifications and adsorption mechanisms with the biochar in nature (BCM). The biochars were characterized by Point-of-zero charges (pHpzc), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The studies showed that the adsorption behavior varied with the pH of the solution. The adsorption study verified that the activated biochars presented better results, so in the kinetic study, the adsorption behavior occurred rapidly in the initial minutes until stabilizing within 3–4 h, better fitting the Elovich model. Isotherm models were tested, where the experimental data were adjusted to the Sips model, with an adsorption capacity of 18 mg g−1 for acid-activated biochar (BCH3PO4) and KOH-activated biochar (BCKOH) with 366.49 mg g−1. The results showed that biochars, especially BCKOH, become viable for production because they are a low-cost material and highly effective in removing drugs.

KOH-activated biochar and chitosan composites for efficient adsorption of industrial dye pollutants

The treatment of dye pollutants remains a challenge in the current management of the water environment. In this study, an innovative biochar material co-modified with KOH and chitosan was synthesized. The morphology and physicochemical properties of the modified biochar material were assessed by SEM, FTIR, XPS, XRD, and thermogravimetric analyses. The results revealed a significant enhancement in chitosan loading due to the pretreatment of biochar with KOH. The co-modified biochar with KOH and chitosan (CHKBC) exhibited an enriched composition of functional groups such as − COOH, −NH2, and − OH, leading to a substantial increase in the maximum adsorption of MB by the biochar from 8.83 mg g−1 to 62.04 mg g−1, a 7.03-fold increase. The excellent adsorption performance of CHKBC for MB was maintained at different solution temperature (288–––318 K) and pH (5–––11) conditions. The main adsorption mechanisms of MB removal by CHKBC involved ion exchange, pore filling, electrostatic attraction, π - π interactions, and hydrogen bonding. Overall, CHKBC has higher chitosan loading, more uniform chitosan distribution, and better adsorption efficiency of MB. It is a promising adsorption material with low cost and a simple production process.

Effects of water washing and KOH activation for upgrading microalgal torrefied biochar

Torrefaction is an effective pathway for microalgal solid biofuel upgrading, and alkali metal activation is also an efficient method to enhance fuel properties. This study explores the comparison of torrefaction alone and KOH activation combined with torrefaction to determine a better operation for biochar production from the microalga Nannochloropsis Oceanica. The results indicate that the HHV ranges of KOH-activated biochar and unactivated biochar are 25.611–32.792 MJ·kg−1 and 25.024–26.389 MJ·kg−1, respectively. Furthermore, KOH-activated biochar is better than unactivated biochar, with less residue, broader pyrolysis and combustion temperature ranges, higher elemental carbon, and less combined carbon. Moreover, KOH-activated biochar is close to the unactivated one from the viewpoint of expense calculation and life cycle assessment and thus possesses a better comprehensive performance. Overall, KOH activation is an efficient method for upgrading microalgal solid biofuel. The results are conducive to exploring further modification of microalgal solid biofuel production with better properties, thus leading to a greener and more efficient approach for upgrading fuel performance.

Zolmitriptan-functionalized graphene oxide and its composite with [Bmim][FeCl4] ionic liquid and biochar derived from the pyrolysis of Heracleum Persicum for supercapacitor application

Graphene oxide (GO) based electrodes often exhibit poor electrochemical performance due to agglomeration. Here, GO was functionalized with the expired heteroatom-rich pharmaceutical compound of Zolmitriptan (ZOL-FGO) as a redox-active spacer to alleviate the mentioned issue. Next, to enhance the electrochemical performance, KOH-activated biochar derived from Heracleum Persicum seeds (HP) through pyrolysis (as a reaction medium) and 1‑butyl‑3-methylimidazolium tetrachloroferrrate ([Bmim][FeCl4]) ionic liquid (IL) (as a conductivity enhancer) were synthesized and physically composited with the ZOL-FGO. Evaluation of the electrochemical behavior of ZOL-FGO/HP/IL electrode in a three-electrode (3E) system revealed the hybrid supercapacitor nature and recorded a specific capacitance (Cs) of 522 F g−1 at 1 A g−1 and a Cs retention of 97.3 % over 10,000 cycles at 8 A g−1. Moreover, the ZOL-FGO/HP/IL//ZOL-FGO/HP/IL electrode was designed and analyzed in the two-electrode (2E) system to determine its practicability. This electrode recorded a Cs of 245 F g−1 at 1 A g−1, a Cs retention of 95.3 % over 10,000 cycles at 8 A g−1, and a power density of 900 W kg−1 at the energy density of 41.35 Wh kg−1. The results confirmed that the synergistic effect of the synthesized materials could be promising in constructing a high-performance hybrid supercapacitor.

Effective Use of Sugarcane-Bagasse-Derived KOH-Activated Biochar for Remediating Norfloxacin-Contaminated Water.

Bagasse-derived biochar (SCB750) was prepared at 750 °C using Chinese sugarcane bagasse as a carbon source and then modified with KOH for the removal of the antibiotic norfloxacin (NOR) from aqueous solutions. 3K-SCB750, prepared using a solid-to-liquid mass ratio of bagasse:KOH = 1:3, was found to have the best adsorption performance for NOR. Under the conditions of pH 5, 25 °C, 2.4 g L-1 adsorbent, and 300 mg L-1 NOR, its adsorption of NOR reached equilibrium (97.5% removal) after 60 min. The adsorption behaviours were in line with the quasi-second-order kinetic and Langmuir isotherm models, respectively. The maximum theoretical adsorption capacity reached up to 157.4 mg·g-1 at 40 °C. The thermodynamic parameters showed that the adsorption of NOR onto 3K-SCB750 was a spontaneous, endothermic, and physical process. In addition, Brunauer-Emmett-Teller analysis (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy were conducted to investigate the structural and adsorption properties of 3K-SCB750. Fourier transform infrared spectroscopy (FTIR) was also applied to understand the mechanism of adsorption of NOR onto 3K-SCB750. All of the results indicated that 3K-SCB750 had a large specific surface area of 1038.8 m2·g-1, an average pore size of 1.9 nm, and hierarchical structures with random pores and cracks for efficient removal of NOR. NOR adsorption mechanisms on 3K-SCB750 were related to the pore-filling effect and electrostatic attraction. Therefore, 3K-SCB750 biochar may be used as a promising adsorbent of antibiotics in wastewaters.

High-efficient removal and adsorption mechanism of organic dyes in wastewater by KOH-activated biochar from phenol-formaldehyde resin modified wood

The treatment of wastewater contaminated with organic dyes has become an intricate challenge in water pollution control. Currently, sophisticated chemical modifications and synthetic methods are frequently needed to enhance the adsorption capacity of biochar for removing dyes during the treatment process. In order to develop a facile, low-cost and efficient biochar absorbent, an activated biochar (KOH/PF-WB) was successfully synthesized from phenol-formaldehyde (PF) resin modified wood via pyrolysis and potassium hydroxide (KOH) activation. Based on the joint effect of PF resin and wood, KOH/PF-WB-700–2 exhibited a remarkable porous structure and abundant oxygen-containing functional groups, which resulted in a substantially high specific surface area (SBET = 2301.61 m2/g) and total pore volume (Vtotal = 1.205 cm3/g). Additionally, the PF resin modification led to increased disorder and more defect sites of activated wood biochar. As a result, KOH/PF-WB-700–2 demonstrated superior adsorption capacity for congo red (3472.22 mg/g) and methylene blue (1112.35 mg/g) dyes compared to some reported adsorbents. The adsorption process could be better described by the pseudo-second-order kinetic model and Langmuir isotherm model, while the overall process was spontaneous and feasible. The primary adsorption mechanism involved pore filling through the modulation of PF resin, along with the cooperative effects of electrostatic attraction, hydrogen bonding and π-π interaction. This finding provides a viable strategy for the waste PF-modified wood cyclic application, and offer technical support for the prospect of KOH/PF-WB for the removal of organic dyes.

Effect of introducing chemically activated biochar as support material on thermal properties of different organic phase change materials

Chemically activated biochar with richer pore structure and higher specific surface area is well suited for loading phase change materials (PCMs). However, the effect of structural characteristics and abundant surface functional groups of chemically activated biochar on the thermal properties of PCMs has not been systematically investigated. Here, shape-stable samples were prepared by introducing biochar obtained by activation with different chemical reagents (ZnCl2, H3PO4, KOH, and K2CO3) into three organic PCMs (paraffin, stearic acid, and polyethylene glycol). The results indicated that the biochar activated by KOH possessed the highest specific surface area of 1344.45 m2/g, followed by biochar activated by ZnCl2, H3PO4, and K2CO3 of 1297.35, 1062.74, and 891.38 m2/g, respectively. The loading capacity of KOH-activated biochar was as high as 82.12 %, 83.13 %, and 80.81 % for the three organic PCMs, and the melting enthalpies of corresponding composite PCMs were 163.82, 168.54, and 139.96 kJ/kg. Additionally, the influence degree on the enthalpies of the three PCMs was only 10.84 %, 12.26 %, and 7.74 %, while that of ZnCl2 and H3PO4-activated biochar was as high as 53.61 % and 44.22 %, 52.10 %, and 57.74 %, 55.35 % and 45.79 % indicating the two biochar were not suitable as support materials for PCMs. Moreover, ZnCl2-activated biochar has the most apparent upgradation on PCMs' thermal conductivity, which could increase the thermal conductivity of the three organic PCMs by 1.318, 1.34, and 1.229 times, respectively, followed by H3PO4, K2CO3, and KOH-activated biochar.

Survey on Lombardy Region Wastewater Effluents and Application of Biochar from Biological Sewage Sludge for Wastewater Treatment

Due to decreasing rainfall, drought is an environmental problem becoming even more alarming every year. The direct reuse of treated wastewater (WW), in compliance with current legislation, can be one of the applicable solutions to deal with water scarcity. In this study, an analysis of wastewater treatment plants (WWTPs) (>400 population equivalent) in the Lombardy region (Northern Italy) was performed to identify the most critical parameters in their effluents (total and ammonia nitrogen, and phosphorous). Biochar filters, as final adsorption means for WWTP effluents, could improve water quality for direct reuse. Biochar from biological sewage sludge produced by an urban WWTP (130,000 population equivalent) was prepared via pyrolysis (350–650–950 °C) and chemical activation with KOH. In each preparation step, the material was analyzed to follow the physicochemical transformations. The removal efficiency of COD, N-NH4+, N-NO3-, and P from real WW was studied using batch adsorption tests. Pyrolysis at 650 °C + KOH activation guaranteed higher yields for N-NH4+ (32%), P (44%), and N-NO3− (66%) with a contact time in the batch test of 6 h for N-NH4+ and P, and 3 h for N-NO3−. Up to 50% COD removal was achieved in 6 h with 950 °C pyrolyzed + KOH-activated biochar.

Adsorption of total petroleum hydrocarbon in groundwater by KOH-activated biochar loaded double surfactant-modified nZVI

Introduction: Crude oil and petroleum hydrocarbon contamination is commonly found in the soil and groundwater during the various processes of mining, processing, and utilization due to issues such as inefficient environmental management, random wastewater discharge, and storage tank leakage.To address this issue, we will use corn stalk biochar (SBC) and surfactants to improve the stability and chemical reactivity of nZVI, thereby enhancing its ability to remove pollutants, and explore the adsorption effect and mechanism of composite materials for petroleum hydrocarbons.Methods: Modified corn stalk biochar (SBC) was synthesized through high-temperature carbonization and KOH activation. Subsequently, the iron/carbon composite PN-nZVI@SBC (PNMSBC) was prepared by loading nano zero-valent iron modified with dual surfactants, and it was adopted to adsorb total petroleum hydrocarbons(TPH) in groundwater. The physical and chemical properties, surface patterns, and elemental mapping of PNMSBC particles were analyzed using SEM, EDS, TEM,XRD, BET, and FTIR spectroscopy. Kinetics and isotherm tests were performed to evaluate the adsorption properties of the composites. TPH adsorption was dependent on ionic strength, initial TPH concentration, as well as pH. The adsorption mechanism combining XPS and EPR spectroscopy was explored.Results: The characterization results by SEM and TEM showed that the particle size of nZVI particles modified by surfactants became smaller, and the dispersibility was enhanced. The characterization results by XRD and FTIR confirmed the successful preparation of the composites. The BET results showed that MSBC and PNMSBC were mesoporous structures. The characterization results indicated that Polyvinylpyrrolidone (PVP) and Sodium oleate (NaOA) inhibited the oxidation of nZVI while effectively improving its reactivity. The result of the experiments on adsorption showed that the removal of TPH by PNMSBC followed Freundlich isotherm and pseudo-second-order kinetic models, thus suggesting that the main adsorption processes comprise chemisorption and multilayer heterogeneous adsorption. The adsorption capacity of PNMSBC was increased by the abundance of macro and microporous structures. To be specific, a maximum Langmuir adsorption capacity (qm) was achieved as 75.26 g/g. The result of batch experiments indicated that PNMSBC continuously removed considerable TPH under a wide pH range from 2 to 6. The adsorption mechanism of PNMSBC includes surface adsorption, oxidation, complexation, and electrostatic interaction.Discussion: In brief, PNMSBC has a promising application for the adsorption of TPH in groundwater remediation.

Low-carbon magnesium potassium phosphate cement (MKPC) binder comprising caustic calcined magnesia and potassium hydroxide activated biochar from softwood technical lignin

Biochar augmentation in cementitious materials is attractive for enhancing the products' mechanical properties and improving sustainability. Softwood technical lignin biochar (5 wt-%) was used to augment MKPC as a replacement material, with increased surface area through KOH activation. Hard-burned (1000 °C) MgO was used as precursor. XRD and SEM-EDX analyses showed “struvite-K” as the primary component of the MKPC materials. MKPC materials including the 2-hour KOH-activated biochar showed the lowest porosity, highest strength and stiffness. Replacing MKPC with KOH-activated biochar can increase strength properties and reduce MKPC binder usage, providing a sustainable approach for precast applications.

Green conversion of wood plastic composites: A study on gasification with an activated bio-char catalyst

The excessive use of wood plastic composites (WPCs) at construction sites owing to their outstanding properties has caused serious disposal problems recently. Thermochemical conversions, such as pyrolysis and gasification, provide a solution for WPC disposal as a means of biofuel generation in an environmentally friendly manner. In this study, air gasification of WPCs was performed over activated bio-char-based catalysts for green valorization with the aim of achieving higher H2 generation. The KOH activation resulted in a significant increase in the Brunauer-Emmett-Teller surface area (14 times) and total pore volume (∼6.7 times), and KOH activated char was an excellent adsorbent for trapping tar, resulting in higher tar conversion into lighter hydrocarbons and H2. In addition, KOH-activated biochar showed the highest gas yield (69 wt%) and highest H2 selectivity (29.76 vol.%) compared to non-catalytic and non-activated bio-char catalysts. In contrast, an equivalence ratio of 0.20 was considered optimal over KOH-activated biochar for obtaining a higher H2 selectivity (29.76%) and minimum CO2 (17.08%). The increased catalyst/feedstock ratio from 0.1 to 0.2 also enhanced the conversion of WPC toward H2 generation (29.76%–35.93%). Finally, the Ni loading over KOH-activated biochar provided the highest H2 selectivity of 43% owing to the synergy of tar cracking, water gas shift reaction, and steam and dry reforming reactions. The increase in the H2 content of the product gas was significant because it increased the overall heating value and quality of the obtained gas. Largely, this study will be a stepping stone toward sustainable valorization of WPC over activated biochar-based catalysts for higher H2 generation.

Application of a KOH-activated biochar for the activation of persulfate and the degradation of sulfamethoxazole

In this work, valorized biomass was simultaneously pyrolyzed and activated with potassium hydroxide to produce a biochar with specific surface area of 1148 m2g−1, i.e. ten times greater than the pristine material, and significant amounts of surface oxygen species and carbonates, as evidenced by XRD and FTIR characterization. The activated biochar (50–250 mgL−1) was employed for a first time as sodium persulfate (100–750 mgL−1) activator to induce the adsorption/oxidation of sulfamethoxazole (SMX: 0.25–1.5 mgL−1), a representative emerging micropollutant, in various water matrices, including the detailed study of different parameters in wastewater. In general, the degradation follows pseudo-first order kinetic law and the apparent constant was found to increase with increasing biochar, persulfate concentration and acidity of the solution and decreasing with SMX concentration, matrix complexity (from surface water or ultrapure water to actual or simulated wastewater). The mechanism of oxidation is mainly through radical pathway and/or electron transfer, while singlet oxygen’s contribution is inconsiderable, as evidenced by scavenging experiments and the structure of the various identified transformation products.

Role of biochar-based catalysts in microwave-induced biomass pyrolysis: Structural properties and modification with Fe-series metals

Biochar-based catalysts have great potential for microwave-induced biomass pyrolysis due to the combination of their excellent microwave absorption performance, good porous structure, and high catalytic activity. In this work, the potential of biochar-based catalysts for microwave-induced catalytic biomass pyrolysis to produce gaseous fuel and upgrade bio-oil was explored and the role of the structural characteristics and Fe-series modification was revealed. The results indicated that the catalytic performance of pure biochar was influenced by their microstructures, and the KOH-activated biochar with abundant microporous structures could effectively promote the gas yields from biomass pyrolysis under microwave heating conditions. With the loading of Fe0 crystal nanoparticles on biochar, the catalytic activity of biochar was greatly enhanced, resulting in an increase in combustible gas (CO, H2 and CH4) yield by 50 % compared to pure biochar, reaching 502.09 mL/g at 650 °C, as well as significant simplification of the bio-oil. Furthermore, the Fe-series alloy crystals exhibit superior catalytic activity over Fe0, further improving gas yields and promoting bio-oil upgrading. The biochar loading of Fe0.64Ni0.36 nanoparticles resulted in a combustible gas yield as high as 574.84 mL/g, and the production of hydrocarbons was greatly enhanced, with a high relative content of 33.9 % in bio-oil. Biochar-based CoFe nanoparticles promoted selective production of H2, with a yield as high as 230.84 mL/g, and the content of mono-phenols in the bio-oil was improved to 74.0 % with the composition of a high phenol relative content of 17.508 %, a trans-isoeugenol relative content of 17.260 %, and a guaiacol relative content of 12.780 %.

Cellulose Fiber Rejects as Raw Material for Integrated Production of Pleurotus spp. Mushrooms and Activated Biochar for Removal of Emerging Pollutants from Aqueous Media.

Cellulose fiber rejects from industrial-scale recycling of waste papers were dried and de-ashed using a combined cyclone-drying and sieving process. The upgraded fiber reject was used as a component of substrates for the cultivation of Pleurotus ostreatus and Pleurotus eryngii mushrooms. Acetic acid (AA) and acid whey (AW) were used to adjust the pH of fiber reject-based substrates. Spent substrate (SMS) was used for the production of activated biochar using H3PO4 and KOH as activating agents and pyrolysis temperatures of 500, 600, and 700 °C. The effectiveness of the biochars in removing pollutants from water was determined using acetaminophen and amoxicillin. By using a feeding rate of 250 kg/h and a drying air temperature of 70 °C, the moisture content of the raw fiber rejects (57.8 wt %) was reduced to 5.4 wt %, and the ash content (39.2 wt %) was reduced to 21.5 wt %. Substrates with 60 and 80 wt % de-ashed cellulose fiber were colonized faster than a birch wood-based control substrate. The adjustment of the pH of these two substrates to approximately 6.5 by using AA led to longer colonization times but biological efficiencies (BEs) that were higher or comparable to that of the control substrate. The contents of ash, crude fiber, crude fat, and crude protein of fruit bodies grown on fiber reject-based substrates were comparable to that of those grown on control substrates, and the contents of toxic heavy metals, that is, As, Pb, Cd, and Hg, were well below the up-limit values for food products set in EC regulations. Activated biochar produced from fiber reject-based SMS at a temperature of 700 °C resulted in a surface area (BET) of 396 m2/g (H3PO4-activated biochar) and 199 m2/g (KOH-activated biochar). For both activated biochars, the kinetics of adsorption of acetaminophen and amoxicillin were better described using the general order model. The isotherms of adsorption were better described by the Freundlich model (H3PO4-activated biochar) and the Langmuir model (KOH-activated biochar).

Dense and uniform growth of TiO2 nanoparticles on the pomelo-peel-derived biochar surface for efficient photocatalytic antibiotic degradation

To clarify the impact of TiO2 growth and deposition on an activated biochar substrate and disclose the deciding mechanistic aspect in photocatalysis, we report TiO2 nanoparticle growth and deposition on the pomelo-peel-derived activated biochar surface by a combined process of liquid-phase deposition in the presence of KOH-activated biochar and then pyrolysis in the air. The TiO2 growth process is investigated by varying the liquid-phase deposition duration. Initially, TiO2 grows over the surface of activated biochar into small microcrystallites, leaving much bare surface of the activated biochar. Prolonging the growth time allows the growth to be saturated and gives rise to dense and uniform TiO2 nanoparticles (with an average size of about 28 nm) over the activated biochar surface, with strengthened interfacial contact. The overgrowth is not favorable for the uniform dispersion of TiO2 nanoparticles while forming large-size aggregates with weakened interfacial contact between TiO2 and activated biochar. Meanwhile, the graphitic domains of the underlying activated biochar substrate are significantly restored, with the Raman D-to-G band intensity estimated to be 0.05, contrasting to 0.95 for the activated biochar. Some surface functional groups of the activated biochar participate in anchoring TiO2 nanoparticles, especially C-OH. The optimal activated biochar-TiO2 composite is stable and exhibits efficient and robust photocatalytic degradation of tetracycline antibiotics, with the photocatalytic reaction rate constant estimated to be 0.021 min−1. More importantly, the determining factor that affects the photocatalytic performance is disclosed to be the photogenerated charge carrier separation capability.

Production of highly porous biochar via microwave physiochemical activation for dechlorination in water treatment

Most biomass is composted into low-grade biofertilizer or processed into energy fuel for burning. At the same time, waste palm shell is potentially converted into highly porous biochar for dechlorination in water treatment. A single-mode microwave activation was developed to perform microwave activation that incorporated the application of steam, KOH, and a physiochemical process. The single-mode microwave activation was performed at the activation temperature ranging from 550–600 °C and recorded a short process duration of 5 min. The steam-activated biochar showed a mass yield of 88.3 wt%, a surface area of 527.4 m2/g, and a dechlorination efficiency of 25.5 mg/g. KOH-activated biochar showed a mass yield of 90.5 wt%, a surface area of 301.1 m2/g and a dechlorination efficiency of 24.0 mg/g. The physiochemical activated biochar showed the highest pores surface area of 717.8 m2/g and dechlorination efficiency of 35.8 mg/g but the lowest mass yield of 77.6 wt%. The results demonstrate that the greater the surface area, the higher the dechlorination efficiency. Using microwave heating and physiochemical activation technology demonstrates a promising way to produce activated biochar for the dechlorination of drinking water.

Designer biochar with enhanced functionality for efficient removal of radioactive cesium and strontium from water

Radioactive elements released into the environment by accidental discharge constitute serious health hazards to humans and other organisms. In this study, three gasified biochars prepared from feedstock mixtures of wood, chicken manure, and food waste, and a KOH-activated biochar (40% food waste + 60% wood biochar (WFWK)) were used to remove cesium (Cs+) and strontium (Sr2+) ions from water. The physicochemical properties of the biochars before and after adsorbing Cs+ and Sr2+ were determined using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, extended X-Ray absorption fine structure (EXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX). The WFWK exhibited the highest adsorption capacity for Cs+ (62.7 mg/g) and Sr2+ (43.0 mg/g) among the biochars tested herein. The removal of radioactive 137Cs and 90Sr exceeded 80% and 47%, respectively, in the presence of competing ions like Na+ and Ca2+. The functional groups present in biochar, including –OH, –NH2, and –COOH, facilitated the adsorption of Cs+ and Sr2+. The Cs K-edge EXAFS spectra revealed that a single coordination shell was assigned to the Cs–O bonding at 3.11 Å, corresponding to an outer-sphere complex formed between Cs and the biochar. The designer biochar WFWK may be used as an effective adsorbent to treat radioactive 137Cs- and 90Sr-contaminated water generated during the operation of nuclear power plants and/or unintentional release, owing to the enrichment effect of the functional groups in biochar via alkaline activation.

Simultaneous removal of cadmium, lead, chromate by biochar modified with layered double hydroxide with sulfide intercalation

In this study, a novel KOH-activated biochar modified with Mg2Al-LDH with S2− intercalation (KBC-LDH-S) was proposed for simultaneous adsorption of anions and cations. The adsorption capacity, thermodynamic and kinetic studies, effects of initial temperature and solution pH were investigated. Furthermore, the adsorption characteristics in both single and ternary Pb-Cd-Cr systems were investigated. Comparing with bare biochar, the adsorption capacity of KBC-LDH-S was increased by 387.8 % for Cd2+ (190.4 mg/g), 358.1 % for Pb2+ (392.2 mg/g), 1106.0 % for total Cr (170.7 mg/g) and 4602 % for Cr6+ (833.8 mg/g). The S2− intercalation effectively increased the adsorption capacity of CrO42− by 3370 % and promoted simultaneous adsorption. The interlayer anion exchange and redox reaction occurred between CrO42− and S2− to generate Cr3+, and then promoted the adsorption of CrO42−. Besides, the adsorption amount and total removal efficiency first increased and then decreased with the increasing concentration in the Pb-Cd-Cr ternary system.

Conversion of Industrial Sludge into Activated Biochar for Effective Cationic Dye Removal: Characterization and Adsorption Properties Assessment

This paper presents an in-depth characterization of a raw industrial sludge (IS-R) and its KOH-activated biochar pyrolyzed at 750 °C (IS-KOH-B) followed by their application to remove a cationic dye from aqueous solution. Materials characterization shows that compared to the IS-R, the IS-KOH-B has improved structural, textural, and surface chemical properties. In particular, the IS-KOH-B’s BET surface area and total pore volume are about 78 and 6 times higher than those found for the IS-R, respectively. The activated biochar efficiently retained the cationic dye under wide experimental conditions. Indeed, for an initial dye concentration of 50 mg L−1, removal yields were assessed to be more than 92.5%, 93.5%, and 97.8% for a large pH range (4–10), in the presence of high contents of competing cations (3000 mg L−1 of Ca2+, Mg2+, Na+, and K+), and a low used adsorbent dose (1 g L−1), respectively. The Langmuir’s adsorption capacities were 48.5 and 65.9 mg g−1 for of IS-R and IS-KOH-B, respectively, which are higher than those reported for various adsorbents in the literature. The dye removal was found to be monolayer, spontaneous, and endothermic for both the adsorbents. Moreover, this removal process seems to be controlled by chemical reactions for IS-KOH-B whereas by both physico–chemical reactions for IS-R. This study demonstrates that the raw industrial sludge and especially its KOH-activated derived biochar could be considered as promising adsorbents for the removal of dyes from aqueous solutions.