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This study focuses on the preparation of activated carbon using a petroleum-residue-based pitch, as well as the HCl gas adsorption properties of the resulting activated carbon pellets relative to their specific surface area and pore structure. Activated carbon was prepared under various oxidation and chemical activation conditions using pitch with a softening point of 220 °C. The activated carbon was mixed with distilled water, an acrylic binder, and carboxymethyl cellulose in a specific ratio to form pellets. These pellets were then dried in an oven at 80 °C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analyses were performed to evaluate the surface structure and specific surface area of the finalized pellets. HCl gas was adsorbed at a concentration of 50 ppm while examining the adsorption characteristics relative to the pore structure and specific surface area.

In this work, carbon dots were created from activated and non-activated pyrolytic carbon black obtained from waste tires, which were then chemically oxidized with HNO3. The effects caused to the carbon dot properties were analyzed in detail through characterization techniques such as ion chromatography; UV-visible, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy; ζ potential; transmission electron microscopy (TEM); and spectrofluorometry. The presence of functional groups on the surface of all carbon dots was revealed by UV-visible, FTIR, XPS, and Raman spectra. The higher oxidation degrees of carbon dots from activated precursors compared to those from nonactivated precursors resulted in differences in photoluminescence (PL) properties such as bathochromic shift, lower intensity, and excitation-dependent behavior. The results demonstrate that the use of an activating agent in the recovery of pyrolytic carbon black resulted in carbon dots with different PL properties. In addition, a dialysis methodology is proposed to overcome purification obstacles, finding that 360 h were required to obtain pure carbon dots synthesized by a chemical oxidation method.

Industrial wastewaters contain persistent and toxic organic compounds that pose a significant risk to public health and the environment upon release. Phenol and its derivatives are examples of such pollutants. Activated carbon, often sourced from unconventional materials like plant biomass, provides a sustainable solution for treating wastewater. This research focuses on creating activated carbon from date nuts through chemical activation with phosphoric acid. The effectiveness of this carbon in removing pentachlorophenol (PCP) from secondary wastewater (SWW) is evaluated. The analysis of the date nut activated carbon (DAC) includes studying its adsorption capacities for iodine and Methylene Blue, surface functional groups, and the point of zero charge (pHpzc) compared to a commercial activated carbon (CAC). The DAC demonstrates promising adsorption capacities, with values of 368.03 mg/g for iodine and 619.9 mg/g for Methylene Blue, which are close to those of the CAC (444.17 mg/g and 620.25 mg/g, respectively). Both DAC and CAC exhibit acidic surface functionalities, with pHpzc values below 10. The efficiency of PCP removal from SWW contaminated with PCP (100 mg/L) reaches 78% within 72 hours. This study indicates that using DAC for PCP removal from SWW is a sustainable approach for wastewater treatment, potentially allowing for the reuse of non-traditional water sources.

The concentration of CO2 in the atmosphere has been increasing and is soon to reach a threatening level for life on the planet. Porous carbons made from biobased materials including from waste resources can be applied to selectively adsorb CO2 from large industrial sites and then lower atmospheric CO2 emissions. In this work, we synthesized highly porous carbons from lemon-peel wastes using two-step activation process involving hydrothermal carbonization followed by chemical activation with KOH, and KOH + alum at 800 °C. The sample activated with KOH + alum has the highest BET surface area (2143 m2/g) and total pore volume of 1.3 cc/g. Although the KOH activated sample has a lower surface area (1113 m2/g), it has better CO2 adsorption capacity ranging up to 4.5 mmol/g because of its well-developed pore structures and a high proportion (90 %) of micropore distributions. The isosteric heat of adsorption lower than 40 kJ/mol indicated that adsorption is mainly driven by physisorption. Better CO2/N2 selectivity suggested a high affinity of the activated carbons towards CO2. Particularly, the sample activated with KOH had selectivity in the range of 20 at the highest adsorption temperature (40 °C), making it a potentially viable option for direct CO2 adsorption applications from large industrial sources.

Adsorption of CO2 by solid sorbents has been proposed as a pathway to decrease the emissions associated with combustion of fuels. However, if employing the waste residues of the combustion process (e.g. biomass combustion bottom ash), a pathway towards a green circular zero-waste and zero-emissions economy may be achieved. As such, a carbonaceous adsorbent has been produced (via chemical activation) using biomass combustion bottom ash as a precursor. This process entailed an intelligently designed experimental campaign based on a randomised Taguchi L9 orthogonal array, which revealed moderate activation temperatures (∼625 °C) and times (30 min) coupled with high ramp rates (10 – 15 °C/min) to be preferable. Following this method, a highly microporous (∼93 %) material was produced possessing a surface area of 643.6 m2/g. This, in turn, facilitated a substantial increase in CO2 uptake, namely, 1.29 mmol/g at 50 °C (quadruple that of the parent carbon and double that of the physically activated counterpart). Additionally, the working capacity as well as the heat of adsorption were measured. The latter properties are often overlooked with main focus drawn towards purely the adsorption capacity; however, they are imperative for industrial deployment of CO2 adsorbents.

[Display omitted] This study investigates the effects of high-power laser irradiation on multilayer MoS 2 , a promising material for catalysis, optoelectronics, and energy applications. In addition to previously reported sculpting of MoS 2 layers, we discovered a novel effect of laser-induced photothermal heating that drives the chemical activation of MoS 2. The photothermal effect was confirmed by temperature-dependent experiments, in situ temperature measurements with nanolocalized probes, and simulations. Remarkably, we observed the reduction of Ag+ ions on laser-irradiated MoS 2 layers, forming plasmonic nanostructures without external stimuli such as photons or chemical reducing agents. We attribute this phenomenon to the significant defect density within the laser-carved region and the surrounding area induced by photothermal effects. Further functionalization of the laser-modified MoS 2 with 4-nitrobenzenethiol self-assembled monolayers demonstrated a significant increase in photocatalytic activity, close to 100% yield compared to the negligible activity of pristine material. Our findings contribute to a deeper understanding of the light-induced modification of MoS 2 properties and introduce a novel method for spatially controlling the chemical activation of MoS 2. This advancement holds significant potential in developing high-performance 2D semiconductors as nano-engineered catalytic materials. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective biosorbents derived from biowaste are highly demanding to handle various environmental challenges, and demonstrate the remarkable synergy between sustainability and innovation. In this study, the extraction of uranium U(VI) was investigated on biowaste activated carbon (BAC) obtained by chemical activation (phosphoric acid) using Albizia Lebbeck pods as biowaste. The biowaste powder (BP), biowaste charcoal (BC) and BAC were evaluated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) with nitrogen adsorption for thermal properties, chemical structures, porosity and surface area, respectively. The pHPZC for acidic or basic nature of the surface and X-ray diffraction (XRD) analysis were performed for BAC. The morphological and elemental analysis were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The extraction of uranium U(VI) ions from aqueous solutions using BAC as sorbent was investigated by using different variables such as pH, contact time, initial uranium U(VI) concentration and BAC dose. The highest adsorption (90.60% was achieved at 0.5 g BAC dose, 2 h contact time, pH 6, 10 ppm initial U(VI) concentration and with 200 rpm shaking speeds. The production of this efficient adsorbent from biowaste could be a potential step forward in adsorption of uranium to meet the high demand of uranium for nuclear energy applications. [ABSTRACT FROM AUTHOR]

Biomass-derived products are a promising way to substitute the necessity for petroleum-derived products, since lignocellulosic material is widely available in our atmosphere and contributes to the reduction of greenhouse gases (GHGs), due to zero net emissions of CO2. This study explores the impact of temperature and molarity on the pyrolysis of açaí seeds (Euterpe oleracea, Mart.) activated with KOH and subsequently on the yield of bio-oil, hydrocarbon content of bio-oil, antioxidant activity of bio-oil, and chemical composition of the aqueous phase. The experiments were carried out at 350, 400, and 450 °C and 1.0 atmosphere, with 2.0 M KOH, and at 450 °C and 1.0 atmosphere, with 0.5 M, 1.0 M, and 2.0 M KOH, at laboratory scale. The composition of bio-oils and the aqueous phase were determined by GC-MS, while the acid value, a physicochemical property of fundamental importance in biofuels, was determined by AOCS methods. The antioxidant activity of bio-oils was determined by the TEAC method. The solid phase (biochar) was characterized by X-ray diffraction (XRD). The diffractograms identified the presence of Kalicinite (KHCO3) in biochar, and those higher temperatures favor the formation peaks of Kalicinite (KHCO3). The pyrolysis of açaí seeds activated with KOH show bio-oil yields from 3.19 to 6.79 (wt.%), aqueous phase yields between 20.34 and 25.57 (wt.%), solid phase yields (coke) between 33.40 and 43.37 (wt.%), and gas yields from 31.85 to 34.45 (wt.%). The yield of bio-oil shows a smooth exponential increase with temperature. The acidity of bio-oil varied between 12.3 and 257.6 mg KOH/g, decreasing exponentially with temperature, while that of the aqueous phase varied between 17.9 and 118.9 mg KOH/g, showing an exponential decay behavior with temperature and demonstrating that higher temperatures favor not only the yield of bio-oil but also bio-oils with lower acidity. For the experiments with KOH activation, the GC-MS of bio-oil identified the presence of hydrocarbons (alkanes, alkenes, cycloalkanes, cycloalkenes, and aromatics) and oxygenates (carboxylic acids, phenols, ketones, and esters). The concentration of hydrocarbons varied between 10.19 and 25.71 (area.%), increasing with temperature, while that of oxygenates varied between 52.69 and 72.15 (area.%), decreasing with temperature. For the experiments with constant temperature, the concentrations of hydrocarbons in bio-oil increased exponentially with molarity, while those of oxygenates decreased exponentially, showing that higher molarities favor the formation of hydrocarbons in bio-oil. The antioxidant activity of bio-oils decreases with increasing temperature, as the content of phenolic compounds decreases, and it decreases with increasing KOH molarity, as higher molarities favor the formation of hydrocarbons. Finally, it can be concluded that chemical activation of açaí seeds with KOH favors not only the yield of bio-oil but also the content of hydrocarbons. The study of process variables is of utmost importance in order to clearly assess reaction mechanisms, economic viability, and design goals that could be derived from chemically activated biomass pyrolysis processes. The study of the antioxidant properties of pyrolysis oils provides insight into new products derived from biomass pyrolysis. [ABSTRACT FROM AUTHOR]

The aim of the present work was to prepare an activated carbon from new precursor Asphodelus microcarpus using KOH as an impregnating agent, in two steps and in the absence of nitrogen. Its preparation requires a pre-carbonization at 500 °C for 60 min in order to obtain the char. Then activation of the char is realized by using KOH using as activating agent variable impregnation ratio: char/activating agent. Calcination is then carried out at 750 °C and 850 °C for 1 hour without azote. The determination of the optimum conditions is carried out by measuring the iodine number and that of methylene blue. The characterization of the chosen product is carried out by the following techniques: BET, FTIR-ATR, SEM and DRX. Under optimum conditions with mass ratio 1:4 at 750 °C (the calcination temperature), the specific surface area is equal to 1025.75 m².g-1 and we obtain micromeso activated carbon. The adsorption kinetics of dye chosen agrees with the pseudo-second-order model, and it appears that Freundlich (two parameters model) and Redlich-Peterson (three parameters model) describe better the adsorption data. Error analysis also showed that the Freunlich model better described the adsorption of Eriochrome Black T compared with the three parameter models. [ABSTRACT FROM AUTHOR]

In this study, we have successfully synthesized a high surface area of activated carbons (ACs) from cocoa pod husk (CPH) by using a combination of hydrothermal carbonization (HTC) and chemical activation in the presence of ZnCl2 as both of catalyst as well as activating agent. During HTC, the effect of HTC temperature (200 and 225℃) and ZnCl2 to biomass mass ratio (1:1, 2:1, 3:1) as a catalyst to the characteristics of the obtained hydrochar (HC) and ACs were investigated. The obtained hydrochar (HCs) was then processed by using ZnCl2 chemical activation with a fixed HC to ZnCl2 mass ratio of 1:4 and the mixture was pyrolyzed at 600 ℃ for 1 h under an inert atmosphere. The results showed that the addition of catalyst during HTC presented different AC morphology, where the carbon samples were decorated with carbon microspheres. An increase of surface area was observed, where the ACs synthesized from catalyzed HC at biomass to ZnCl2 ratio of 1:3 at temperature 200 ℃ gave a higher surface area of 1954 m2/g compared to that of without catalyst (1165 m²/g). The catalysis effect was more profound at the HTC temperature of 200 ℃ compared to 225 ℃, as reflected in the significant increase of AC surface area. The addition of a catalyst creates ACs with narrow pore distribution compared to that of synthesized in the absence of a catalyst. It was also observed that the ACs from catalyzed hydrochar possessed higher oxygenated functional groups (OFG) than those without catalysts. [ABSTRACT FROM AUTHOR]

The preparation of eco-friendly activated carbons (ACs) has gained significant attention due to their enhanced ability to remove a wide range of pollutants from water. Agricultural waste materials are promising precursors for the preparation of ACs due to their abundant availability and low cost. For the first time, this study is dedicated to preparing activated carbon from the useless leaves of sugar beet (LSB). This was conducted by thermo-chemical activation using H3PO4 as a robust activating agent. The activation process was carried out in a programmable furnace at a fixed temperature of 550 °C for 2 h. Different ratios of H3PO4 (85%) and pristine LSB (0.5:1, 1:1, 2:1, and 3:1) were used to produce four synthesized ACs, which were labeled as AC(0.5:1), AC(1:1), AC(2:1) and AC(3:1), respectively, for evaluating the impact of the impregnation ratios on the properties of these synthesized ACs. The as-synthesized ACs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller surface area (SBET) analysis. Among all the prepared ACs, AC(2:1) showed the highest degree of amorphicity, which resulted in the highest SBET value of 700.71 m2/g. This high surface area suggests a magnificent porous structure and surface chemistry of the synthesized AC, making it suitable for various environmental applications. The study shows that the thermo-chemical activation of sugar beet leaves with H3PO4 can produce a highly competent AC with excellent characteristics that can be used in waste management, water purification, and other related applications. Overall, this study highlights the potential of using useless LSB as a sustainable source of AC production and provides new insights into the preparation and characterization of eco-friendly ACs. [ABSTRACT FROM AUTHOR]

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The preparation of activated carbons (ACs) from cherry stones and chemical activation with H3PO4 can be controlled by the experimental variables during the impregnation step in order to obtain a tailored porous structure of the as-prepared ACs. This control not only extends to the ACs' texture and porosity development, but also to the chemical nature of their surface. The spectroscopic and elemental characterization of different series of ACs is presented in this study. The spectroscopic band features and assignments strongly depend on the H3PO4 concentration and/or the semi-carbonization treatments applied to the feedstock before impregnation, which ultimately influence different characteristics such as the AC hydrophilicity. Different surface chemistries arise from the different tailored impregnation solutions, showing a practical outcome for future applications of the as-prepared ACs. [ABSTRACT FROM AUTHOR]

In this study, using waste materials such as hard almond bark and palm kernels, the porous activated carbon has been synthesized by chemical activation method with activation agents of sodium hydroxide (NaOH), sodium chloride (NaCl), and phosphoric acid (H3PO4). Then, the structural, morphological, and optical properties of the synthesized activated carbons were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy. The XRD patterns showed that an activated carbon structure was formed in all the samples synthesized with chemical activators. The SEM and TEM images showed that there is no porosity and pitted for raw and primary carbon samples of hard almond bark and palm kernels, but for activated carbon by various activating agents, it was clearly porous structure in the activated samples. Also, in the FTIR spectra of activated carbon, it was confirmed that there are carbon single and double bonds for in all samples. The measurement of the optical absorption coefficient (α) and optical band gap (Eg) of porous carbon nanostructures showed that α is in order of 106–107 cm−1 and energy gap is in range of 1.98–2.83 eV. The activated carbon sample synthesized from almond bark with H3PO4 activator has highest energy gap (Eg = 2.83 eV) and NaCl activator has lowest energy gap (Eg = 1.98 eV). [ABSTRACT FROM AUTHOR]

Activated carbon is the preferred adsorbent for gas and water treatment in various industry across the world due to its efficiency, reliability, and accessibility. Recently, in Malaysia, studies are mainly focused on the fabrication of activated carbon from lignocellulosic biomass-based precursors from agricultural waste such as coconut shell, rice husk, and palm kernel shell. Activated carbon fabrication is a two-step process; the precursor will first undergo carbonization, then, activation is carried out either physically or chemically to develop its porous surface for adsorption purposes. The main benefit of activated carbon is the customizable pore structure for different utilization, which can be easily achieved by the chemical activation process. The types and concentration of chemicals used for activation, pre-treatment of precursor, duration of the activation process, and the mass ratio of precursor to chemicals are proven to effectively influence the resulting pore structure. However, the chemicals used in the activation process can be harmful to the environment. Thus, the chemical recovery process is necessary after the activation process. Nonetheless, more in-depth research on producing activated carbon from abundant biomass materials with bio-based chemical agents for activation is needed to achieve an ecological and sustainable manufacturing process. [ABSTRACT FROM AUTHOR]

In this study, activated carbon was synthesized using the almond shell and palm kernel by physical activation with water vapor and chemical activation with phosphoric acid (H3PO4) methods. Then, the structural and optical properties of the activated carbons were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The SEM images showed that in the raw sample of hard almond shell and palm kernel, there is no porosity and pores, but in the activated carbon samples, porosity and structural defects were clearly observed. The XRD patterns showed that porous and amorphous structure was formed in all samples synthesized with physical and chemical activation. The results of FTIR spectra of activated carbons showed that there are carbon functional groups in all samples. The optical absorption coefficient (α) of the activated carbon with physical and chemical activation methods was obtained in order of 105–106. The band gap measurement of porous nanostructures showed that the activated carbon synthesized with chemical and physical activation methods have energy gap (Eg) in region = 2.80 to 3.15 eV and urbach energy (EU) in region = 120 to 210 meV. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the properties of carbon materials prepared from apricot stones by carbonization at 300–900 °C and chemical activation by KOH with different ratios between components. It was found that increasing the carbonization temperature to 800–900 °C leads to the degradation of narrow micropores and the carbon matrix. The adsorbent materials were characterized with FTIR and SEM, and a specific surface area was calculated. Moreover, additional activation by HNO3 and annealing at 450 °C led to an increase in surface area up to 1300 m2/g. The obtained N-enriched sorbents show adsorption activities of 190–235 mg/g for methylene blue and 210–260 mg/g for methyl orange. The results of this study can be useful for future scale-up using the apricot material as a low-cost adsorbent for the removal of dyes in environmental remediation production. [ABSTRACT FROM AUTHOR]

Wastewater containing dyes are released into water bodies generating serious problems in human health and marine life. To contribute to the solution of this problem, a novel activated carbon was prepared from untreated pine (Pinus radiata) sawdust by dry chemical activation with ZnCl2 and was used for wood dye adsorption. The carbon was characterized by point of zero charge, N2 and CO2 adsorption isotherms, SEM-EDX, and FTIR. N2 and CO2 surface areas were 471.4 and 319.5 m2 g−1, respectively, with 91% of micropores. Wood dye adsorption was studied in function of pH (2–12), adsorbent dose (0.1–4 g L−1), time (up to 48 h for blue and red and 12 h for black), and initial concentration (5–500 mg L−1). The equilibrium data for the blue and black dyes were satisfactorily fitted to the Freundlich model while those for the red dye to the Langmuir model. Kinetic data were explained by the pseudo-second order (chemisorption process) and intraparticle diffusion models. At 5 mg L−1, a 100% removal efficiency was achieved at all pH for the blue dye, whereas for the red and black, natural pH (5.1) and pH = 2, respectively, led to the best removal efficiencies, 96 and 56%. Increasing concentration above 25 mg L−1 significantly reduced adsorption efficiency for blue and red dyes. For the black dye increasing the dose to 1 g L−1, the adsorption efficiency reached 82% at 25 mg L−1. High removal efficiencies were achieved for all dyes at 25 mg L−1 and 4 g L−1. [ABSTRACT FROM AUTHOR]

Currently, carbon derived from biomass waste or residues is being intensively utilized as electrodes due to its excellent electrical properties, including high conductivity, appropriate porosity, and a specific surface area suitable for supercapacitor applications. Despite its advantages, the performance of supercapacitors made from biomass-derived carbon is insufficient for engineering applications because of the challenges in obtaining the mesoporous structure of activated carbon (AC). Therefore, this study highlights the potential of biomass-based carbon as the electrodes of a highly efficient supercapacitor, which can facilitate highly efficient current transport in energy storage systems. It comprehensively discusses various biomass material sources and activation methods to produce carbon, with a focus on the physical and electrical properties. Initially, the study discusses carbon activation methods and mechanisms to understand why activating agents and electrolyte solutions have a high specific surface area and specific capacitance. It then concentrates on the chemical activation method and its importance in making AC useful as an efficient electrode. Finally, in this study, various biomass sources were discussed to highlight the performance of supercapacitors electrodes originating from agricultural and wood residues relating to the specific capacitance and capacitance retention. Based on the obtained results, it is concluded that biomassbased carbon materials could be the most advantageous platform material for energy conversion and storage. [ABSTRACT FROM AUTHOR]

Water pollution remains a global problem that urges researchers to develop new technologies aimed at environmental restoration. Here, this study aimed at obtaining an activated biochar from pequi almonds for dye removal. Before and after adsorption, the materials underwent characterization using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TG). The biochar from the pequi almond was called BA, and the activated biochar from the pequi almond was called ABA. The influence of the pH, contact time, and adsorbate concentration on adsorption was investigated using the dye methylene blue. The morphological assessment revealed higher cracks and pores in the ABA than in the BA. The TG showed that the BA lost approximately 19% more mass than the ABA, indicating that activation occurred. The activation contributed to the decrease in the degree of disorder in the BA because of the increased number of graphitic carbon atoms (ordered) in the ABA, as observed via Raman. The adsorption kinetics followed a pseudo-second-order model, while the adsorption isotherms followed the Langmuir model. The BA adsorption capacity was 500.00 mg g−1, constituting a robust solution for dye removal from aqueous environments. Therefore, this implies the success of the process. [ABSTRACT FROM AUTHOR]

The increasing accumulation of rock waste obtained due to ore processing and its environmental impacts, such as acid mine drainage and elevated concentrations of heavy metals in soils, necessitates the transformation of mining technologies based on the concept of circular waste management. The research is aimed at improving the parameters of the mechanical activation effect produced on technogenic georesources, as well as at expanding the application scope of disintegrators in the field of using the partial backfill of the mined-out space when developing stratified deposits. In this regard, the research purpose was to substantiate the parameters of extracting metals from enrichment tailings using their mechanochemical activation to ensure cyclic waste management. The research involved the application of three-dimensional interpolation methods used for processing the data and the graphical representation. As a result, the following was found to be characteristic of the waste of the Sadonsky mine management. The degree of extracting zinc from pre-activated tailings increases logarithmically when the H2SO4 concentration and the NaCl proportion decrease 3.5 times. The degree of extracting lead from the activated tailings increases according to the Fourier law when decreasing the NaCl mass concentration, and an optimal range of the H2SO4 (0.38–0.51%) proportion decreases six times. One of the key results of the research is the justification of expanding the scope of applying disintegrators in the case of a directed activation influence exerted on the components of the stowing strips. The obtained results expand the understanding of the mechanism of the influence of the mechanochemical activation of dry tailings on the reactivity unevenness when extracting several metals from them. [ABSTRACT FROM AUTHOR]

The removal of heavy metals from wastewater has become the subject of considerable interest at present. Thus, the use of novel adsorbents that are highly efficient is of critical importance for the removal of Cr (VI) ions from aqueous media. The adsorption of Cr (VI) ions from aqueous solutions by a new adsorbent, cedar wood sawdust, and the optimization of its adsorption parameters, were investigated in this study. Cedar wood sawdust was used in its native and HNO3/NaOH chemically modified forms as new low-cost sorbents to remove Cr (VI) ions from aqueous solutions in a batch system. The adsorption conditions were analyzed via response surface methodology. The RSM results showed that the optimal adsorption conditions yielding the best response were an adsorbent mass of 2 g for native Cedar and 1.125 g for its activated form, a metal concentration of 150 mg/L for native Cedar and 250 mg/L for activated, a temperature of 50 °C, a pH of 1, and a contact time of 67.5 min. At optimum adsorption conditions, the maximum adsorption capacities and the adsorption yields were 23.64 mg/g and 84% for native Cedar and 48.31 mg/g and 99% for activated Cedar, respectively. [ABSTRACT FROM AUTHOR]

In the current investigation, carbon-based solid acid catalysts were synthesized from peanut shells (PSs) and rice straw (RS) using ZnCl2 activation and concentrated sulfuric acid sulfonation. These catalysts were then employed for the hydration of pinene to produce terpineol. The research findings suggest that the natural porous structure of RS is more amenable to ZnCl2 activation compared to PSs. Furthermore, the catalysts prepared from fully activated RS by ZnCl2 (RSA-C-S) had a higher SBET and higher density of oxygen-containing groups (–COOH) in comparison with unactivated RS-based solid acids (RSC-S). The characterization outcomes revealed that RSA-C-S possesses a specific surface area of 527.0 m2/g, significantly outperforming RSC-S, which has a surface area of 420.9 m2/g. Additionally, RSA-C-S registered a higher –COOH density of 1.37 mmol/g, as opposed to RSC-S's, with 1.07 mmol/g, attributable to the partial oxidation of internal –OH groups during activation. Experimental data from hydration tests confirmed that the catalyst's superior performance is largely attributed to its elevated specific surface area and a high density of –COOH functional groups. Under optimal reaction parameters, RSA-C-S demonstrated unparalleled catalytic efficiency in the synthesis of α-terpineol via hydration of α-pinene, achieving conversion and selectivity rates of 87.15% and 54.19%, respectively. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) is a widely used adsorbent that can be applied to remove lead (Pb(II)) ions from wastewater. In the current work, carrageenan was used as a precursor to prepare carraggenan based activated carbon (CAC) using potassium hydroxide (KOH) as a chemical activating agent for Pb(II) ions adsorption from aqueous solution of lead nitrate (Pb(NO3)2). The preparation process involved activation of the carrageenan with KOH at a ratio of 1:4 followed by carbonization at 700oC for 4 h. Physical and chemical characterization of synthesized CAC was conducted to understand surface morphology and functional groups. As the scanning electron microscope (SEM) analysis found, the CAC particle sizes are, on average 25.11 µm before adsorption and 39.21 µm after adsorption. Functional group studies proved that the adsorbate had been adsorbed into the CAC by showing a band stretch of the nitrile group in the Fourier transform infrared (FTIR) spectroscopy analysis. The adsorption process was optimized by changing the temperature of adsorption, dosage of adsorbent, and initial concentration of adsorbate. At the optimum conditions, maximum Pb(II) ions adsorption on the CAC was achieved by 99.04%. Throughout this study, the highest capacity of CAC was determined to be 1.95 mg/g, while the minimum capacity was found to be 0.19 mg/g. Langmuir and Freundlich isotherm were studied to understand adsorption mechanisms. The results suggested that the Langmuir isotherm model fits better than the Freundlich model with a regression coefficient -2 of 0.9845. Pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. Pseudo-second-order exhibited the best fit data for kinetic studies with a regression coefficient of -2 0.9996, indicating that the adsorption of lead using CAC is limited by the chemisorption process. [ABSTRACT FROM AUTHOR]

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor for obtaining nanostructured activated carbons by chemical activation with various reagents. The obtained activated carbons were characterized using nitrogen adsorption–desorption isotherms, ash content, Boehm titration and pH of water extracts. It was shown that the choice of activator had an important effect on the physicochemical and sorption properties of the obtained activated carbons. The specific surface area of the obtained adsorbents ranged from 345 to 1052 m2/g. Chemical activation of the starting material with potassium carbonate made it possible to obtain activated carbons with the strongest developed specific surface area and the best sorption capacity against the tested pollutants. 1 g of this carbon is able to adsorb 1215 mg of iodine and 454 mg of methylene blue. The least effective adsorbent turned out to be the carbon obtained by chemical activation of fennel seeds with sodium carbonate, whose sorption capacity toward the pollutants from aqueous solutions was 77 mg/g and 317 mg/g for methylene blue for iodine, respectively. The alkaline pH of the solution promotes effective adsorption of methylene blue on the surface of the obtained adsorbents. The reaction of the dye molecules adsorption on the activated carbons occurs according to the pseudo-second-order model. The Langmuir isotherm best described the process under study. In addition, it was shown that chemical activation of fennel seeds leads to carbon adsorbents with acidic surface character. The negative values of Gibbs free energy indicate the spontaneous character of the process. The study has shown that fennel seeds can be successfully used to obtain low-cost and effective nanostructured carbon adsorbents with good sorption capacity toward organic and inorganic contaminants, from the aqueous phase. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective biosorbents derived from biowaste are highly demanding to handle various environmental challenges, and demonstrate the remarkable synergy between sustainability and innovation. In this study, the extraction of uranium U(VI) was investigated on biowaste activated carbon (BAC) obtained by chemical activation (phosphoric acid) using Albizia Lebbeck pods as biowaste. The biowaste powder (BP), biowaste charcoal (BC) and BAC were evaluated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) with nitrogen adsorption for thermal properties, chemical structures, porosity and surface area, respectively. The pHPZC for acidic or basic nature of the surface and X-ray diffraction (XRD) analysis were performed for BAC. The morphological and elemental analysis were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The extraction of uranium U(VI) ions from aqueous solutions using BAC as sorbent was investigated by using different variables such as pH, contact time, initial uranium U(VI) concentration and BAC dose. The highest adsorption (90.60% was achieved at 0.5 g BAC dose, 2 h contact time, pH 6, 10 ppm initial U(VI) concentration and with 200 rpm shaking speeds. The production of this efficient adsorbent from biowaste could be a potential step forward in adsorption of uranium to meet the high demand of uranium for nuclear energy applications.

The objective of the present work was to synthesize a graphene-like structure from petroleum coke (pet coke). Graphene is a potential alternative conducting material to replace traditional electrode materials such as indium tin oxide. The phosphoric acid was used to activate the pet coke in conditions where the coke to acid ratio is varied as 1:1, 1:2, 1:3, 1:4 and 1:5. The samples were kept at different temperatures in the furnace maintained in inert atmospheric conditions at 400, 500 and 600 °C for activation time intervals of 1, 2 and 3 h. The extent of activation of pet coke samples was characterized by their yield and iodine number. For the optimized conditions (600 °C, 3 h, 1:4 coke to acid ratio), the activated pet coke was moulded and taken as the anode for electrochemical exfoliation using platinum wire as cathode, and 0.3 M H2SO4 solution as electrolyte. The electrochemical exfoliation was carried out using DC power supply at 22 V for 8 h, and the obtained exfoliated product was analysed by surface-sensitive techniques (XRD, Raman and SEM). The specific capacitance values were measured using cyclic vol­tammetry in KOH, Na2SO4 and H2SO4 electrolytes. The highest specific capacitance value of 40 F g-1 for the scanning rate of 25 mV s-1 was obtained in 1 M H2SO4. It was confirmed that graphene-like structure produced from activated pet coke can be used as an alternate material for supercapacitor applications.

This study reports on the development of nanocomposites utilizing a mineral inhibitor and a micronutrient filler. The objective was to produce a slow release fertilizer, with zinc sulfate as the filler and halloysite nanotubes as the inhibitor. The study seeks to chemically activate the intercalation of zinc into the macro-, meso-, and micropores of the halloysite nanotubes to enhance their performance. As a result, we obtained three nanocomposites in zinc sulfate solution with concentrations of 2%, 20%, and 40%, respectively, which we named Hly-7Å-Zn2, Hly-7Å-Zn20, and Hly-7Å-Zn40. We investigated the encapsulation of zinc sulfate in halloysite nanotubes using X-ray diffraction analysis, transmission electron spectroscopy, infrared spectroscopy (FTIR), and scanning electron microscopy with an energy-dispersive spectrometer. No significant changes were observed in the initial mineral parameters when exposed to a zinc solution with a concentration of 2 mol%. It was proven that zinc was weakly intercalated in the micropore space of the halloysite through the increase in its interlayer distance from 7.2 to 7.4. With an increase in the concentration of the reacted solution, the average diameter of the nanotubes increased from 96 nm to 129 nm, indicating that the macropore space of the nanotubes, also known as the "site", was filled. The activated nanocomposites exhibit a maximum fixed content of adsorbed zinc on the nanotube surface of 1.4 wt%. The TEM images reveal an opaque appearance in the middle section of the nanotubes. S SEM images revealed strong adhesion of halloysite nanotubes to plant tissues. This property guarantees prolonged retention of the fertilizer on the plant surface and its resistance to leaching through irrigation or rainwater. Surface spraying of halloysite nanotubes offers accurate delivery of zinc to plants and prevents soil and groundwater contamination, rendering this fertilizer ecologically sound. The suggested approach of activating halloysite with a zinc solution appears to be a possible route forward, with potential for the production of tailored fertilizers in the days ahead. [ABSTRACT FROM AUTHOR]

Efficient production of activated carbon (AC) depends on variables such as feedstock properties, preparation conditions, and activating agents. This study aimed to identify optimal conditions for AC production from African Oil Bean (Pentaclethra macrophylla) Pods (PMps) using potassium hydroxide (KOH) and phosphoric acid (H3PO4) as activating agents. Through a systematic iodine adsorption characterization approach and leveraging Response Surface Methodology as a chemometric tool, the study fine-tuned chemical activation and carbonization parameters (temperature, time, and impregnation ratio) for producing PMACs. The adjustments directly impacted the iodine number (In) and yields (Cy) of the PMACs (PMAC-KOHop and PMAC-H3PO4op). The predicted In and Cy values closely aligned with the observed values – (PMAC-KOHop: 918.58 mg/g predicted vs. 916.56 mg/g observed; PMAC-H3PO4op: 593.44 mg/g predicted vs. 592.88 mg/g observed) and (PMAC-KOHop: 39.60% predicted vs. 39.15% observed; PMAC-H3PO4op: 51.30% predicted vs. 51.10% observed), demonstrating precision of the production process. Key structural properties, including BET specific surface areas (SSA), total pore volumes (Vt), and average pore diameters, exhibited notable differences between the PMAC-KOHop and PMAC-H3PO4op, with the former demonstrating superiority. Particularly, FTIR spectra highlighted higher aromaticity in PMAC-KOHop, revealing the preference for KOH over H3PO4 in the chemical activation of PMps. The high In achieved with the PMAC-KOHop indicated its efficacy as a pollutant adsorbent, aligning with the established attributes of commercial granular activated carbons for pollutants removal from wastewater. This study establishes PMps as a dependable AC precursor, emphasizing the advantages of KOH over H3PO4 in chemical activation. Future research should be directed at investigating PMAC-KOHop adsorption capabilities for diverse pollutants and exploring PMps' potential contributions to metallic or nanocomposite formations with other adsorbents. [ABSTRACT FROM AUTHOR]

In this study, we systematically study the efficient production method and electrochemical characteristics of activated carbons (AC) derived from rice husk (RH) and walnut shell (WS). In particular, the effectiveness of physical activation using carbon dioxide (CO2) was investigated and compared with the more common chemical activation method using potassium hydroxide (KOH). The results show that the KOH–activated samples have remarkable specific capacities, reaching 157.8 F g−1 for RH and 152 F g−1 for WS at 1 A g−1. However, the rate capability of AC obtained via KOH decreases significantly as the scanning rate increases, retaining only 51.5% and 68% of their original capacities for RH–KOH and WS–KOH, respectively, at 20 A g–1. In contrast, CO2–activated samples show a superior rate performance with a capacity retention of 75.6% for WS and 80% for RH at the same current density. In addition, electrochemical impedance spectroscopy (EIS) analysis shows that AC obtained via CO2 has a lower charge transfer resistance compared to its KOH counterparts. CO2–activated RH and WS electrodes show Rct values of 0.1 Ω and 0.24 Ω, respectively, indicating improved ion transport kinetics and surface area utilization. These results highlight the importance of activation techniques in tailoring the electrochemical behavior of biomass–derived carbon. This study not only expands the understanding of the interaction between activation, morphology, and performance but also indicates the potential of CO2 activation as an environmentally friendly and efficient alternative. As the field of sustainable energy storage advances, this work provides valuable guidance for the development of high–performance supercapacitor electrodes with less environmental impact. [ABSTRACT FROM AUTHOR]

The adsorption of aniline from aqueous solution on carbon sorbents is investigated. The sorbents are derived from D and G Kuznetsk Basin coal by chemical activation using potassium hydroxide at 800°C, when the coal/alkali ratio (by mass) is 1.0 : 0.5 and 1.0 : 1.0. The sorbents consist mainly of micropores, and their specific surface is relatively high (700–1340 m2/g). The experimental adsorption isotherms are plotted. On that basis, the parameters of the Langmuir, Freundlich, Dubinin–Astakhov, and BET sorption models are calculated. The models are appropriate for the description of aniline adsorption (R2 > 0.9). The Langmuir model is the most accurate. The state parameters indicate that the adsorption of aniline by this means is very effective. The process may be described as monomolecular adsorption on the surface of microporous sorbents. The thermomechanical characteristics of the adsorption process are low. That indicates physical adsorption. [ABSTRACT FROM AUTHOR]

Benzene vapor is notoriously known to induce adverse human health, which plays a definite role in the deformation of cells. Various advanced adsorbents from lignocellulosic precursors have emerged as cheaper alternatives to the green process for the adsorption of gaseous benzene. In this paper, the prominence mainly benzene vapor removal with lignin-based adsorbent in the adsorption technology has investigated the textural, morphology, and chemical characteristics of activated carbon synthesized from Fraxinus excelsior L. seeds, a lignocellulosic biomass waste. Chemically starting HCl and KOH in the N2 atmosphere was adopted, contributing to the porous carbon material's well-developed porosity and surface chemistry. Also, carbonaceous materials were investigated by Brunauer–Emmet–Teller (BET), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction. Herein, the optimum way for producing activated carbon was recognized to be: activation temperature of 800 and 700 °C in line with an impregnation weight ratio of samples to HCl 1:2 and KOH 1:3 for 2 h activation time as FE7AC and FE22AC, which have resulted in 676 m2/g and 0.39 cm3/g; 734 m2/g and 0.48 cm3/g of BET surface area and total pore volume, respectively. The SEM observations exhibited advanced high porosity development formed by oxidation–reduction reaction, while FTIR confirmed the presence of various surface functional groups. Moreover, benzene became more tremendously facile for four ambient temperatures (20, 25, 30, and 35 °C) and until 200 min contact time. The tremendous values varied from 96 to 224 mg/g and 122 to 286 mg/g depending on lignin-based adsorbent amounts as 0.5 or 1 g and an initial benzene concentration of 100 mg/m3 by using FE7AC and FE22AC. The main innovation of this paper is exciting to assist recent paths for optimizing air filtration procedures under actual environmental circumstances, particularly regarding its compatibility with the benzene molecular structure of FE22AC. The paper concludes that the performance of the FE22AC can be enhanced via improvements in its surface properties for a wide array of actual benzene concentrations from gaseous applications. [ABSTRACT FROM AUTHOR]

This paper studies the chemical and mechanochemical preparation of glauconite with ammonium dihydrogen phosphate (ADP) nanocomposites with a ratio of 9:1 in the vol.% and wt.%, respectively. The methods include X-ray diffraction analysis, scanning electron microscope with energy-dispersive X-ray spectroscopy, transmission electron microscopy, infrared spectroscopy, and differential thermal analysis with a quadruple mass spectrometer. The manufactured nanocomposites keep the flaky glauconite structure. Some glauconite unit structures have been thickened due to minimal nitrogen (ammonium) intercalation into the interlayer space. The globular, granular, or pellet mineral particles of nanocomposites can be preserved via chemical techniques. Globular and micro-aggregate particles in nanocomposites comprise a thin film of adsorbed ADP. The two-step mechanochemical method makes it possible to slightly increase the proportion of adsorbed (up to 3.2%) and intercalated (up to 6.0%) nutrients versus chemical ways. Nanocomposites prepared via chemical methods consist of glauconite (90%), adsorbed (1.8–3.6%), and intercalated (3.0–3.7%) substances of ADP. Through the use of a potassium-containing clay mineral as an inhibitor, nitrogen, phosphorus, and potassium (NPK), nanocomposite fertilisers of controlled action were obtained. Targeted and controlled release of nutrients such as phosphate, ammonium, and potassium are expected due to various forms of nutrients on the surface, in the micropores, and in the interlayer space of glauconite. This is confirmed via the stepwise dynamics of the release of ammonium, nitrate, potassium, and phosphate from their created nanocomposites. These features of nanocomposites contribute to the stimulation of plant growth and development when fertilisers are applied to the soil. [ABSTRACT FROM AUTHOR]

In this study, activated carbons were produced through the chemical activation of caraway seeds using three different activators: Na2CO3, K2CO3, and H3PO4. A 1:2 weight ratio of precursor to activator was maintained in every instance. Comprehensive analyses were conducted on the resultant activated carbons, including elemental analysis, textural parameters determination, Boehm titration for surface oxygen functional groups, pH assessment of aqueous extracts, and quantification of ash content. The produced materials were subjected to adsorption tests for methylene blue and methyl red sodium salt from the liquid phase and the effects of adsorbent dosage, pH of the aqueous dye solution, process temperature, and adsorbent–adsorbate contact time on sorption capacity obtained. To characterize the adsorption model of the examined pollutants, both the Langmuir and Freundlich equations were employed. In addition, the sorption capacity of the obtained carbon materials against an iodine aqueous solution was assessed. The specific surface area of the obtained adsorbents ranged from 269 to 926 m2/g. By employing potassium carbonate to chemically activate the starting substance, the resulting activated carbons show the highest level of specific surface area development and the greatest sorption capacity against the tested impurities—296 mg/g for methylene blue and 208 mg/g for methyl red sodium salt. The adsorption rate for both dyes was determined to align with a pseudo-second-order kinetic model. The experimental adsorption data for methylene blue were well-described by the Langmuir model, whereas the Freundlich model was found to be congruent with the data pertaining to methyl red sodium salt. [ABSTRACT FROM AUTHOR]

Porous carbon is an emerging material for the capture of CO2 from point sources of emissions due to its high structural, mechanical, and chemical stability, along with reusability advantages. Currently, research efforts are mainly focused on high- or medium-pressure adsorption, rather than low-pressure or DAC (direct air capture) conditions. Highly porous and functionalized carbon, containing heteroatoms (N, O, etc.), is synthesized using different activation synthesis routes, such as hard template, soft template, and chemical activation, to achieve high CO2 capture efficiency at various temperatures and pressure ranges. Fundamental pore formation mechanisms with different activation routes have been evaluated and explored. Higher porosity alone can be ineffective without the presence of proper saturated diffusion pathways for CO2 transfer. Therefore, it is imperative to emphasize more rational multi-hierarchical macro-/meso-/micro-/super-/ultra-pore design strategies to achieve a higher utilization efficiency of these pores. Moreover, the present research primarily focuses on powder-based hierarchical porous carbon materials, which may reduce the efficiency of the capture performance when shaping the powder into pellets or fixed-bed shapes for applications considered. Therefore, it is imperative to develop a synthesis strategy for pelletized porous carbon and to explore its mechanistic synthesis route and potential for CO2 capture. [ABSTRACT FROM AUTHOR]

Porous Ni-doped copper oxide (NCO) photocatalyst has been produced using chemical activation and metal doping techniques. Structural, optical, morphological, and electrical analyses were performed on copper oxide (CO) and porous NCO photocatalysts. The monoclinic-phased, UV/Vis light-triggered, electrically conductive, and porous-surfaced NCO photocatalyst was successfully synthesized, according to a detailed physicochemical investigation. The photo-decomposition abilities of synthetic porous NCO and counterpart CO photocatalysts were investigated and compared using Allura red (AR). According to the photocatalytic study, the porous NCO photocatalyst outperformed its counterpart (CuO) and eliminated 91.4% (adsorption: 18%; decomposition: 79%) of the AR dye in 48 min. Over the porous NCO photocatalyst, the AR dye disintegrated at a rate of 0.024 min−1, which is more than 1.84 times quicker than the rate of disintegration over the CO photocatalyst. The porous NCO photocatalyst, as synthesized, preserved 88% of its photocatalytic activity after five recyclability tests and had remarkable electron-hole separation activity, according to reusability tests and transient-photocurrent measurements. Also, the radical capture experiment suggested that superoxide and hydroxyl are important for porous NCO's photocatalytic activity. According to the findings of this research, the synthesis of ferromagnetic metal-doped and porous semiconductive materials has a great potential for azo dye breakdown, which makes it an efficient, cost-effective, and environmentally acceptable solution for the clean-up of polluted water. [Display omitted] [ABSTRACT FROM AUTHOR]

Dyes are responsible for major environmental issues globally due to their toxicity, large-scale production, and extensive use in various industrial sectors. Pollution caused by hazardous dyes is mainly due to textile waste, which is constantly discharged into the aquatic system, often causing harm to humans and affecting water quality. In recent years, the removal of dyes from industrial textile wastewater has been a major challenge. Numerous technologies and methods have been developed to remove dyes from wastewater and meet clean water requirements. In this study, the effectiveness of activated carbon prepared by chemical activation of jujube stones for textile wastewater treatment was investigated. The effects of the concentration of H3PO4 and the carbonization temperature on the activated carbon's properties were studied. Several physicochemical methods, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction, methylene blue index, Boehm titration, iodine index and pH point of zero charge, were considered to characterize the produced adsorbents. To assess the quality of the two studied textile effluents (Mustard and Violet), the following parameters were used: biological oxygen demand (BOD), chemical oxygen demand (COD), turbidity, suspended particles and dissolved solids, before and after treatment with the produced activated carbon. Untreated wastewater analysis revealed high values for almost all parameters: pH > 9, COD of 302.72 mg/L and 230.68 mg/L for Mustard and Violet effluent, respectively. Both effluents from an industrial textile factory exhibited a COD/BOD ratio higher than three, which restricts their biodegradability. Examination of the effect of contact time and activated carbon dosage on the treatment of the two effluents showed that 4 g/L of activated carbon and 60 min of contact time were sufficient for optimal treatment, resulting in pollutant removal rates of 81.03 and 84.65% for the Violet and Mustard effluents, respectively. The results of this research highlight the efficiency of activated carbon derived from jujube stones as a cost-effective adsorbent for the treatment of real textile wastewater. [ABSTRACT FROM AUTHOR]

The objective of this research was to produce an activated carbon (AC) from exhausted coffee grounds (ECG) and chemically activate it with natural lye from eucalyptus ash to subsequently evaluate the fluoride adsorption process in an aqueous medium. The thermal analysis of ECG was determined as well as solubilized extraction, alkalinity and calcium content of eucalyptus ashes. AC was characterized by elemental analysis, scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), analysis of textural properties, pH and point of zero charge (PZC). The AC presented macroporosity and XRD confirmed the amorphous characteristic of cellulose-containing materials. Carboxylic acid functional group was identified in the AC surface, which can contribute to the adsorption of fluoride. The specific surface area of ECG and AC were 189.01 and 21.74 m2/g. The adsorption kinetics of fluoride revealed that equilibrium is reached around 800 min and the data followed the pseudo-second order model. The Freundlich model fitted the experimental data with the best quality and Freundlich's constant n allowed inferring that the adsorption is favorable and the isotherm appears to be L-type, with an initial downward curvature, which suggests less availability of active sites when increasing the adsorbent concentration. [ABSTRACT FROM AUTHOR]

The increase in burning, deforestation, and the exorbitant use of fossil fuels have contributed to the increase in carbon dioxide emissions; this gas is responsible for the intensification of the greenhouse effect and radical climate changes. In this way, it becomes necessary to find alternatives to reduce its emission. Porous carbon materials synthesized from lignocellulosic waste can be employed in technologies for capture and utilization of CO2 due to the advantages such as selectivity, low-cost synthesis, high surface area and pore volume, and thermal and chemical stability. Considering the availability of Brazil nut biomass residues in the Amazon region, this article proposes to synthesize activated carbon from the lignocellulosic residue using physical and chemical activation methods for CO2 capture. The analysis of N2 adsorption–desorption isotherms proves the predominance of a microporous structure when using the two synthesis methods described here. In physical activation, the surface area was 912 m2/g, while, in chemical activation, it was 1421 to 2730 m2/g. The sample treated via the chemical method (BS6-K1) showed better performance in CO2 adsorption, with adsorption results of 3.8 and 6 mmol/g of CO2 at 25 ℃ and 0 °C, respectively, at 101 kPa. CO2 adsorption capacity is due to the high volume of ultramicropores. It is believed that the microporous carbon material synthesized from Brazil nut residues is an alternative precursor for carbon materials used as CO2 capture. [ABSTRACT FROM AUTHOR]

The production of activated carbon (AC) from lignocellulosic biomass through chemical activation is gaining global attention due to its scalability, economic viability, and environmental advantages. Chemical activation offers several benefits, including energy efficiency, reduced carbonization time, and lower temperature requirements. In this study, potassium hydroxide (KOH) was employed for chemical activation, resulting in activated carbon with a high specific surface area of ~3050 m2/g. The structural analysis revealed the presence of graphitized carbon in the activated carbon matrix, accounting for over 15%. The X-ray diffraction (XRD) technique was employed to investigate the activated carbon derived from rice husk (RH). The potential applications of activated carbon obtained from rice husks through chemical activation were explored, including its use for heavy metal removal, elimination of organic pollutants, and as an active material in hybrid energy storage devices. Furthermore, a scaling methodology for the production of activated carbon was proposed, facilitating its industrial implementation. [ABSTRACT FROM AUTHOR]

The main challenges in wastewater treatment using adsorbents are the selection, development, and characterization of the absorbents. In this study, activated carbons (ACs) were prepared through chemical activation with phosphoric acid, followed by carbonization of banana root (BR). Proximate, ultimate, BET, FTIR, and FE-SEM analyses were employed to characterize the precursor and prepared ACs. A maximum BET surface area of 989 m 2 / g was observed for one of the ACs. The developed ACs were employed to remove methylene blue (MB) from synthetic wastewater at different initial concentrations (20–200 mg/L) and adsorption temperatures (25, 30, and 40 ∘ C ) for 24 h in a batch mode. Adsorption isotherm models in linear and non-linear forms of Langmuir, Freundlich, and Temkin were considered to analyze experimental equilibrium data. For evaluation of the optimum isotherm, six different error analysis functions were used. Results indicated that the non-linear form of the Temkin isotherm model was the most suitable to explain the adsorption of MB. The maximum adsorption of 152.83 m g / g was observed for an adsorption temperature of 40 ∘ C and an initial concentration of 200 mg/L. The adsorption kinetic data were fitted with two models: pseudo-first-order and pseudo-second-order. The pseudo-second-order model was the best to explain the adsorption mechanism. The Weber and Morris intraparticle diffusion model was used to identify the rate-controlling step. The intraparticle diffusion was not only the rate-controlling step; another step like surface diffusion might also be involved in the adsorption process. Thermodynamic analyses were carried out, which revealed that the adsorption process was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

Here in this work, gum arabic tree seed shell (bio mass) was utilized to synthesize carbon adsorbents by chemical activation methods at constant carbonization temperature. The properties of the carbon adsorbents were estimated through characterization techniques such as X-ray diffraction, Fourier Transform Infrared spectroscopy, Laser Raman spectroscopy, Field Emission Scanning electron microscopy, CHNS-elemental analysis and N2 adsorption studies. Gum arabic tree seed shell–derived carbon adsorbents were examined for CO2 capture in 25 to 70 °C temperature range. The characterization results indicated that these carbons contain high surface area with micro porosity. Among all the carbons, the carbon prepared after treatment of KOH to biomass ratio is 3:1 followed by and carbonization at 750 °C exhibited high adsorption capacity of 3.42 m.mol/g at 25 °C. The reason for high adsorption capacity of the adsorbents mainly depended on surface area (1472 m2/g) and micropore volume. The adsorbents showed easy desorption and recyclable up to five cycles with consistent activity. [ABSTRACT FROM AUTHOR]

Nanoporous carbon materials exhibiting a high specific pore volume and specific surface area are the most effective for most applications in modern industrial production. The technological modes of obtaining a nanoporous material by chemical high-temperature activation are studied. The mechanisms of activation are considered and the main parameters that affect the characteristics of the resulting material are found. On the basis of experimental data, effective values of the technological modes of activation of a carbon material and directions toward further research are proposed. [ABSTRACT FROM AUTHOR]