Search

In this study, the effects of torrefaction (TF) and hydrothermal treatment (HT) on the preparation of activated carbons (ACs) from penicillin mycelia residues (PMR) were investigated. Textural properties, microstructures, graphitization, and surface functional groups of the ACs were examined. The adsorption isotherms and kinetics of ACs for methylene blue (MB) were discussed. The results showed TAC1 exhibited the largest specific surface area (1983.95 m2/g), while TAC0.5 exhibited the largest microporous surface area (1447.88 m2/g). With the increase of the KOH ratio, the pore size distribution of ACs gradually developed to large micropores and mesopores. Raman and FT-IR results showed that all ACs have similar graphitized structures and surface chemistry, although the peak intensities differed. XPS results showed that both BAC0.5 and TAC0.5 contained higher C = O, improving the aromatization, especially BAC0.5. TAC0.5 had the largest adsorption capacity for MB, with adsorption values of 620.16 mg/g at an MB concentration of 1000 mg/L. The isothermal adsorption model showed that the adsorption of ACs for MB was better fitted by the Freundlich than Langmuir models. The adsorption kinetics indicated that the adsorption process of AC0.5, HTAC0.5, and TAC0.5 for MB was mainly chemical adsorption, while that of BAC0.5 was physical adsorption. [ABSTRACT FROM AUTHOR]

From a char of Palm seed (CSP), activated carbon at 973, 1073, and 1173 K was obtained (CASPs). These temperatures developed textural properties to favor the adsorptive properties. The CASPs percentage of burning decreased with the increase of the activation temperature from 76 to 26%. These products were obtained with a CO2 flow (as activating gas) and a short time of activation. The CASPs were characterized by mercury porosimetry, adsorption of N2, CO2, and methylene blue at 77, 273, and 298 K, respectively. Wide supermicropores were obtained for CASP1173 and narrow mesoporosity was achieved for CASP973 and CASP11073 (1.4–2.0 nm and 2.0–5.0 nm, respectively). Mercury porosimetry determined that the activated carbons have mesopores with diameters smaller than 50 nm and macropores with diameters greater than 50 nm. The use of Dubinin and Langmuir models showed that the adsorption occurred in the larger diameter micropores and smaller diameter mesopores of the highest and shortest diameters (above 3.85 mmol/g). The activated carbon at 973 K showed a higher methylene blue adsorption capacity (181.03 mg/g). The MB adsorption was determined by the diameters of the adsorbent pores. For this reason, a batch adsorption system to remove this contaminant was proposed. [ABSTRACT FROM AUTHOR]

The sorption of triterpene saponins is studied on different brands of active carbon under equilibrium conditions. The effect the surface activity of glycosides has on the course of the curves is established. Sorption isotherms are assessed using a formal approach based on selecting the sorption equations (Langmuir, Freundlich, BET, Redlich–Peterson) that describe the obtained dependences as closely as possible. Thermodynamic characteristics of the given process (energy of sorption, enthalpy, and entropy) are calculated using sorption curves in the coordinates of the Langmuir equation. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rare earth elements (REEs), comprising seventeen metallic elements, including lanthanides, scandium, and yttrium, are indispensable for modern technological industries due to their unique properties. However, their supply is critically risky for the European Union, with 95% of global production concentrated in China, Brazil, Vietnam, Russia, India, and Australia. This mini-review examines the adsorption of REEs onto pyrolytic carbon-based materials as a sustainable recovery method from secondary raw materials. The review covers different types of carbon-based adsorbents used in several research works, such as activated carbon, chars, and biochar, and discusses their adsorption mechanisms and influencing factors. Comparative analyses of adsorption capacities highlight the significance of surface area and functionalization in enhancing adsorption efficiency. Despite promising results, the variability in adsorption performance due to experimental conditions and the scarcity of real-world application studies are noticed. This review underscores the need for further research using real e-waste leachates to validate the practical applicability of pyrolytic carbon-based adsorbents for REEs' recovery, aiming for an economically and environmentally sustainable solution. [ABSTRACT FROM AUTHOR]

Activated carbons are commonly used for adsorption/depollution applications, but only a few studies are related to their lubricating properties. In order to investigate a new family of friction reducers, the tribological properties of biochars and derived activated carbons obtained from sugar cane bagasse are investigated. Activated carbons are obtained from either a physical (steam water) or chemical (with phosphoric acid) activation process. The tribological tests show that the activated carbons present very low friction coefficients, close to 0.08. The correlation of textural and tribological investigations shows that the specific surface area of the compounds as well as the microporous and mesoporous domain extensions are key parameters to optimize the friction reduction properties of activated carbons. The friction properties of the compounds are improved if the mesoporous domain extension is above 40% of the total porous volume. This study shows that local biomass waste valorization is possible and that sugar cane bagasse-derived activated carbons appear as interesting new friction reduction additives for lubricants. [ABSTRACT FROM AUTHOR]

The essential target of this work was to exploit some locally obtainable hard bio-wastes viz. date pits and pistachio shells, in preparing varioufigs activated carbons (ACs) via the optimised ZnCl2 and H3PO4 activation routes. After preparing ACs from an equal blend of the hard bio-waste, the best samples were identified for their BET surface area and pore volume, X-ray diffraction (×RD), Fourier Transform Infra-Red spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray (EDX). The ACZnCl2 exhibited a higher BET surface area (895.53 m2/g) than the ACH3PO4 (419.60 m2/g). The optimal ACs were implemented in the adsorptive elimination of dibenzothiophene (DBT) from model gasoline. The DBT trials were optimized by investigating the impact of the initial concentration of DBT (25–200 mg/L), ACs mass (0.05–0.40 g), temperature (0.0–60 °C), and working period (5.0–80 minutes). The highest elimination of DBT by ACZnCl2 reached 97.78% using 0.30 g of it at 40°C for 60 minutes employing 25 mL of 200 mg/L DBT, while ACH3PO4 revealed the superlative elimination of DBT (88.46%) utilising 0.35 g of it at 40°C for 70 minutes using 25 mL of 200 mg/L DBT. Besides the kinetics investigations, isothermal studies indicated that the Freundlich isotherm and the pseudo-2nd-order kinetic best described the DBT adsorption by the ACs more than the other models. In a batch process, the adsorption capacities of DBT by both ACZnCl2 and ACH3PO4 were 26.31 mg/g and 20.23 mg/g, respectively. The typical adsorption conditions for each adsorbent were employed to eliminate S- compounds from commercial gasoline and DBT in a fixed-bed system. In conclusion, the ACs above could be reutilised for 5 successive runs with an insignificant loss in their desulphurisation ability. They can thus be recommended for the desulfurization of fuels on an industrial scale. [ABSTRACT FROM AUTHOR]

Natural waters and wastewaters often contain heavy metals, e.g., iron. Iron ore mining contaminates groundwater with iron up to 30 maximal permissible concentrations (MPC) as this element gets washed out from rock and soil. Adsorption is the most effective and economically feasible method of additional purification of natural and wastewater from iron. Its efficiency depends on the type of adsorbent. The research objective was to select the most efficient sorption material to eliminate water from iron, as well as to establish the adsorption patterns for different sorbents, thus creating sustainable and effective purification. The study featured carbonaceous sorbent of the SKD-515 grade, mineral sorption materials with aluminosilicate of the AC grade, and silicate-based sorbent of the ODM-2F grade. The porous structure was studied by porometry methods while the surface image was obtained using scanning electron microscopy. Other indicators included equilibrium, kinetics, and dynamics of iron adsorption by various sorbents. The Freundlich and Langmuir equations made it possible to calculate the key adsorption parameters. The Gibbs energy values were obtained from the Langmuir equation and equaled 11.93–20.66 kJ/mol, which indicated the physical nature of the adsorption process. Under static conditions, the sorbents demonstrated a high adsorption capacity with respect to iron, depending on the structure, and could be arranged as AC > SKD-515 > ODM-2F. In SKD-515, iron adsorption occurred in micropores; in AC and ODM-2F, it took place in mesopores. The kinetics of iron extraction showed that the adsorption process was limited by external mass transfer. The research provided a new understanding of iron adsorption by materials of various structures. The conclusions were supported by scanning electron microscopy images. Initial concentration, flow velocity, and loading layer height were studied in dynamics, i.e., during continuous operation of the adsorption column. The system proved extremely effective and reached 99.0% Fe3+ extraction under the following conditions: flow rate = 1 L/min, loading column height = 0.15 m, column diameter = 0.05 m, initial concentration = 0.5 mg/L (5 MPC). The column performance was tested at an initial concentration of iron ions of 50 MPC, which simulated the wastewater treatment at industrial enterprises. This comprehensive study of iron adsorption from wastewater proved the efficiency of the mineral sorption materials with aluminosilicate of AC grade.

The rise in atmospheric greenhouse gases like CO2 is a primary driver of global warming. Human actions are the primary factor behind the surge in CO2 levels, contributing to two-thirds of the greenhouse effect over the past decade. This study focuses on the chemical activation of avocado seeds with sodium hydroxide (NaOH). The influence of various preparation methods was studied under the same parameters: carbon precursor to NaOH mass ratio, carbonization temperature, and nitrogen flow. For two samples, preliminary thermal treatment was applied (500 °C). NaOH was used in the form of a saturated solution as well as dry NaOH. The same temperature of 850 °C of carbonization combined with chemical activation was applied for all samples. The applied modifications resulted in the following textural parameters: specific surface area from 696 to 1217 m2/g, total pore volume from 0.440 to 0.761 cm3/g, micropore volume from 0.159 to 0.418 cm3/g. The textural parameters were estimated based on nitrogen sorption at −196 °C. The XRD measurements and SEM pictures were also performed. CO2 adsorption was performed at temperatures of 0, 10, 20, and 30 °C and pressure up to 1 bar. In order to calculate the CO2 selectivity over N2 nitrogen adsorption at 20 °C was investigated. The highest CO2 adsorption (4.90 mmol/g) at 1 bar and 0 °C was achieved. [ABSTRACT FROM AUTHOR]

Cellulose microspheres have a wide range of applications due to their unique properties and versatility. Various preparation methods have been explored to tailor these microspheres for specific applications. Among these methods, the acetate method using cellulose acetate is well known. However, replacement of the acetate group through the butyrate group significantly extends the variety of morphological properties. In the present work, microspheres based on cellulose acetate butyrate are being developed with modified characteristics in terms of particle size, porosity, surface morphology and the inner structure of the microspheres. While the inner structure of cellulose acetate microspheres is predominantly porous, microspheres prepared from cellulose acetate butyrate are mainly filled or contain several smaller microspheres. Carbon materials from cellulose acetate butyrate microspheres exhibit a high specific surface area of 567 m2 g−1, even without further activation. Activation processes can further increase the specific surface area, accompanied by an adaptation of the pore structure. The prepared carbons show promising results in symmetrical supercapacitors with aqueous 6 M KOH electrolytes. Activated carbons derived from cellulose acetate butyrate microspheres demonstrate an energy density of 12 Wh kg−1 at a power density of 0.9 kW kg−1. [ABSTRACT FROM AUTHOR]

This study introduces a gamma pretreatment of water hyacinth powder for activated carbon (AC) production with improved electrochemical properties for supercapacitor applications. The structural and morphological changes of post-irradiation were meticulously analyzed using scanning electron microscopy (SEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). The pretreatment significantly modifies the pore structure and reduces the particle size of the resulting activated carbon (WHAC). Nitrogen adsorption-desorption isotherms indicated a substantial increase in micropore volume with escalating doses of gamma irradiation. Electrochemically, the activated carbon produced from pretreated WH at 100 kGy exhibited a marked increase in specific capacitance, reaching 257.82 F g−1, a notable improvement over the 95.35 F g−1 of its untreated counterpart, while maintaining 99.40% capacitance after 7000 cycles. These findings suggest that gamma-pretreated biomasses are promising precursors for fabricating high-performance supercapacitor electrodes, offering a viable and environmentally friendly alternative for energy storage technology development. [ABSTRACT FROM AUTHOR]

This work aims at emphasizing the impact of different physical interactions such as intermolecular ones between co‐adsorbed molecules on the adsorption mechanisms in the liquid phase. Thus, the adsorption of a low concentration (5 ppm) of benzene, phenol, and p‐nitrophenol from aqueous medium in single and binary mixture solutions is studied. Two activated carbons were prepared from two different activating agents and used in this regard. The adsorbed amounts are determined by high‐performance liquid chromatography. The results showed the great importance of the aforementioned interactions in the adsorption of phenol, particularly the interactions with the co‐adsorbed compounds. Indeed, phenol was remarkably better retained in binary mixture solutions than in a single one. [ABSTRACT FROM AUTHOR]

The increasing emissions of gaseous pollutants of anthropogenic origin, such as carbon dioxide (CO2), which causes global warming, have raised great interest in developing and improving processes that allow their mitigation. Among them, adsorption on porous materials has been proposed as a sustainable alternative. This work presents a study of CO2 equilibrium adsorption at low temperatures (0, 10, and 20 °C) over a wide range of low pressures, on activated carbon derived from Eucalyptus (ES) and Patula pine (PP) forest waste, and carbonaceous material derived from waste tires (WT). The precursors of these materials were previously prepared, and their physicochemical properties were characterized. ES and PP were thermochemically treated with phosphoric acid, and WT was oxidized with nitric acid. Additionally, these materials were used to obtain monoliths using uniaxial compaction techniques and different binding agents, with better results obtained with montmorillonite. A total of six adsorbent solids had their textural and chemical properties characterized and were tested for CO2 adsorption. The highest specific surface area (1405 m2 g−1), and micropore properties were found for activated carbon derived from Eucalyptus whose highest adsorption capacity ranged from 2.27 mmol g−1 (at 0 °C and 100 kPa) to 1.60 mmol g−1 (at 20 °C and 100 kPa). The activated carbon monoliths presented the lowest CO2 adsorption capacities; however, the studied materials showed high potential for CO2 capture and storage applications at high pressures. The isosteric heats of adsorption were also estimated for all the materials and ranged from 16 to 45 kJ mol−1 at very low coverage explained by the energetic heterogeneity and weak repulsive interactions among adsorbed CO2 molecules. [ABSTRACT FROM AUTHOR]

In this paper, we provide a comprehensive review of the latest research trends in terms of the preparation, and characteristics of activated carbons regarding CO2 adsorption applications, with a special focus on future investigation paths. The reported current research trends are primarily closely related to the synthesis conditions (carbonization and physical or chemical activation process), to develop the microporosity and surface area, which are the most important factors affecting the effectiveness of adsorption. Furthermore, we emphasized the importance of regeneration techniques as a factor determining the actual technological and economic suitability of a given material for CO2 capture application. Consequently, this work provides a summary and potential directions for the development of activated carbons (AC). We attempt to create a thorough theoretical foundation for activated carbons while also focusing on identifying and specific statements of the most relevant ongoing research scope that might be advantageous to progress and pursue in the coming years. [ABSTRACT FROM AUTHOR]

Vehicular hydrogen has been stored in special tanks at very high pressures (700 bar) with obvious disadvantages in the energy cost of compression and safety. The use of adsorbed H2 instead of compressed H2 can be a solution to enable safer and more economical storage. Conducting experimental studies of H2 adsorption at high pressures may present operational difficulties and risks. In this study we propose the prediction of H2 adsorption up to 700 bar using the Monte Carlo algorithm in the grand canonical ensemble and the representative pores method. The prediction was carried out in eight commercial activated carbons, the results showed a good agreement between the experimental and simulated data. It was possible to determine the maximum pressure where the highest adsorption of H2 occurs at 298 K with emphasis on Maxsorb that reached 6.14 wt % at 700 bar, near the US Department of Energy (DOE) target value of 6.5 wt%. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) materials from renewable sources are widely used in electrochemical applications due to their well‐known high surface area. However, their application as electrode material in double‐layer electrochemical devices may be limited due to their relatively low electrical conductivity and lightweight. To overcome these limitations, the incorporation of pseudocapacitance metal oxide nanoparticles is an optimum approach. These nanoparticles can provide a second energy storage mechanism to the composite, mitigating the loss of surface area associated with their incorporation. As a result, the composite material is endowed with increased conductivity and higher density, making it more suitable for practical implementation in real devices. In this study, we have incorporated a fine dispersion of 1 % of MnO clusters into a highly porous activated carbon synthesized from walnut shells (WAC). The high‐resolution electron microscopy studies, combined with their related analytical techniques, allow us to determine the presence of the cluster within the matrix carbon precisely. The resulting MnO@WAC composite demonstrated significantly improved capacitive behavior compared with the WAC material, with increased volumetric capacitance and higher charge retention at higher current densities. The composite's electrochemical performance suggests its potential as a promising electrode material for supercapacitors, addressing drawbacks associated with traditional AC materials. [ABSTRACT FROM AUTHOR]

The active coals obtained from high-moor peat of the European North of Russia by thermochemical activation with NaOH and various types of pre-treatment (debituminization and pre-pyrolysis) were studied. Based on the results of the low-temperature adsorption of nitrogen, the resulting active coals belonged to adsorbents whose structure was dominated by micropores. The specific surface area of coal pores reached 2330 m2/g, and the total pore volume was 1.44 cm3/g. The introduction of the stage of pre-pyrolysis made it possible to increase significantly the yield of active coals. This increase was 28 or 97% for the initial peat or debituminized samples, respectively; moreover, the sorption characteristics were significantly improved. It has been shown that weakly decomposed high-moor peat of the European North of Russia can be used as a raw material for the production of high-efficiency carbon microporous adsorbents. [ABSTRACT FROM AUTHOR]

This study reveals the impact of the activation with microwave and conventional heating sources on textural properties and CO2 uptake of a mixed plastic-based char. Two mixed plastic-based adsorbents, one activated using microwaves and the other using conventional heating, were produced at optimum activation conditions, and subsequently compared. The findings show that both heating sources produced microporous adsorbents, but activation heating sources influenced their physicochemical properties and CO2 uptake. The microwave-produced activated carbon (AC) displayed superior BET surface area, total, micro- and ultra-micropore volumes compared to the conventionally produced AC. The microwave-produced AC possessed CO2 adsorption capacities of 1.66 and 2.37 mmol/g under dynamic and equilibrium conditions, respectively, at 25 °C and 1 bar. These capacities represent an 8 and 30 % higher uptake, respectively, compared to the 1.53 and 1.66 mmol/g displayed by the conventionally prepared AC under the same adsorption conditions. Both samples displayed stable and excellent CO2 recyclability over 10 adsorption-desorption cycles, with desorption efficiencies ranging from 93.46 % to 96.72 % (microwave- and conventionally- produced ACs respectively). The Avrami model most accurately described the experimental CO2 adsorption data under dynamic conditions, while the Sip model gave the best fit for equilibrium conditions. These findings apply to both types of ACs at various temperatures, irrespective of the heating source. Overall microwave heating is more efficient than conventional heating, requiring 300°C lower temperature, 115 minutes shorter time, 0.79 kWh less energy, and less KOH. It improves CO2 uptake and reduces production costs by 80 %, offering a sustainable alternative for CO2 adsorbent production.

Electrochemical performances of three electrodes (E) fabricated using activated carbons (AC) derived from agricultural biomass waste, specifically argan husks (ah), date seeds (ds) and olive stones (os), denoted ACah-E, ACds-E and ACos-E respectively were evaluated. These activated carbons were produced through a combination of thermal and chemical methods, involving carbonization for 2 hours at a temperature of 900 °C, followed by chemical activation using phosphoric acid as the activating agent. The scanning electron microscope observations revealed that the obtained samples exhibited variable pore size distributions tailored based on the raw materials activated by the same process. Subsequently, cyclic voltammetry, galvanostatic charge-discharge, and electro­chemical impedance spectroscopy were used to characterize the electrochemical performances of ACah-E, ACds-E and ACos-E as supercapacitor electrodes. The results revealed that the ACah-E, ACds-E and ACos-E cells have specific capacitances of 138.26, 50.41 and 34.61 F/g, respectively. These results were found to be influenced by the specific surface areas, which were 476 m²/g for ACah, 441 m²/g for ACds and 362 m²/g for ACos, as determined by the BET method. The behaviour of electrochemical double-layer capacitors (EDLC) in acidic aqueous electrolyte (1 M H2SO4) is demonstrated by these findings, which suggest that the waste materials used may also be prospective candidates for supercapacitor applications, with the best performance for ACah-E than other.

Abstract The design of adsorption processes for pharmaceuticals removal depends not only on the adsorption equilibrium but also on the mass transfer and adsorbate stability, being a problem still not solved the case of degradation products. By selecting different stable (amoxicillin, ciprofloxacin, carbamazepine and ibuprofen) and labile micropollutants (omeprazole) as case studies emerging pollutants, we have quantitatively analysed these effects on activated carbon. For stable compounds, the experimental data were fitted to equilibrium models to obtain information about the different adsorption mechanism depending on the characteristics of the molecules. Mass transfer effects were analysed for all the adsorbates, observing the control of intraparticle pore diffusion mechanism, since the effective pore diffusion coefficient is in the range from 10–8 to 10–10 cm2 h−1. As far as omeprazole is concerned, a kinetic model is proposed for predicting its degradation, identifying the reversibility of several degradation steps. The overall adsorption of OMP and derivates is calculated, observing the pore diffusion is considered as the rate-limiting step. For the first time, a combined model considering the chemical degradation and the adsorption of the degradation products is proposed and experimentally validated. This represents an important step in the modelling of processes leading to the purification of water from this type of pollutant.

Carbonization of biomass residues followed by activation has great potential to become a safe process for the production of various carbon materials for various applications. Demand for commercial use of biomass-based carbon materials is growing rapidly in advanced technologies, including in the energy sector, as catalysts, batteries and capacitor electrodes. In this study, carbon materials were synthesized from hardwood using two carbonization methods, followed by activation with H3PO4, KOH and NaOH and doping with nitrogen. Their chemical composition, porous structure, thermal stability and structural order of samples were studied. It was shown that, despite the differences, the synthesized carbon materials are active catalysts for oxygen reduction reactions. Among the investigated carbon materials, NaOH-activated samples exhibited the lowest Tafel slope values, of −90.6 and −88.0 mV dec–1, which are very close to the values of commercial Pt/C at −86.6 mV dec–1. [ABSTRACT FROM AUTHOR]

Every late autumn, fluttering poplar leaves scatter throughout the campus and city streets. In this work, poplar leaves were used as the raw material, while H3PO4 and KOH were used as activators and urea was used as the nitrogen source to prepare biomass based-activated carbons (ACs) to capture CO2. The pore structures, functional groups and morphology, and desorption performance of the prepared ACs were characterized; the CO2 adsorption, regeneration, and kinetics were also evaluated. The results showed that H3PO4 and urea obviously promoted the development of pore structures and pyrrole nitrogen (N–5), while KOH and urea were more conductive to the formation of hydroxyl (–OH) and ether (C–O) functional groups. At optimal operating conditions, the CO2 adsorption capacity of H3PO4– and KOH–activated poplar leaves after urea treatment reached 4.07 and 3.85 mmol/g, respectively, at room temperature; both showed stable regenerative behaviour after ten adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

This study aims to valorize three agricultural-food (agri-food) wastes: Argan husks, dates seeds, and olive stones collected from various regions of Morocco to produce three types of activated carbons (ACah),(ACds) and (ACos) respectively. These activated carbons were used to compare their effectiveness in removing methyl orange, an organic pollutant in aqueous solutions. The precursor materials were carbonized at a temperature of T=900°C for 2 hours and subsequently chemically activated using phosphoric acid (H3 PO4 ) in a weight ratio of 1:2. The obtained samples were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET-analysis to determine the specific surface area. The analysis revealed that (ACah) displayed a rough surface with more pores and O-H chemical bonds, indicating its superior adsorption properties. This finding corresponds to the BETspecific surface areas obtained, which were 476 m²g-1 for ACah, 441 m²g-1 for ACds, and 362 m²g-1 for ACos. In all methyl orange adsorption experiments (10 mg L-1), 60 mg of each activated carbon was used for 30 minutes, resulting in removal efficiencies of 93.87% for ACah, 91.83% for ACds, and 89.79% for ACos. The examination of adsorption kinetics and isotherm analysis demonstrated a strong alignment of the adsorption data with both the pseudo-second-order and Langmuir models across various materials. [ABSTRACT FROM AUTHOR]

The design of adsorption processes for pharmaceuticals removal depends not only on the adsorption equilibrium but also on the mass transfer and adsorbate stability, being a problem still not solved the case of degradation products. By selecting different stable (amoxicillin, ciprofloxacin, carbamazepine and ibuprofen) and labile micropollutants (omeprazole) as case studies emerging pollutants, we have quantitatively analysed these effects on activated carbon. For stable compounds, the experimental data were fitted to equilibrium models to obtain information about the different adsorption mechanism depending on the characteristics of the molecules. Mass transfer effects were analysed for all the adsorbates, observing the control of intraparticle pore diffusion mechanism, since the effective pore diffusion coefficient is in the range from 10–8 to 10–10 cm2 h−1. As far as omeprazole is concerned, a kinetic model is proposed for predicting its degradation, identifying the reversibility of several degradation steps. The overall adsorption of OMP and derivates is calculated, observing the pore diffusion is considered as the rate-limiting step. For the first time, a combined model considering the chemical degradation and the adsorption of the degradation products is proposed and experimentally validated. This represents an important step in the modelling of processes leading to the purification of water from this type of pollutant. [ABSTRACT FROM AUTHOR]

This work focused on preparing biochars from different biomasses: orange, pomegranate, and watermelon peels, as promising materials for the removal of Cr (VI) removal. Chemical activation was performed using the phosphoric acid at the ratio 2:1 (wt%) between the biomasses and the acid, followed by nitrogen pyrolysis. The physicochemical properties of the activated carbons were characterized via pH of zero charge, Fourier transform infrared spectroscopy, elemental analysis, surface area, nitrogen adsorption–desorption isotherms, particle size distribution, and scanning electron microscopy-energy-dispersive X-ray spectroscopy. Changing the precursor type had significant effect on the porous structure of the produced activated carbon. Pomegranate-based biochar exhibited the highest specific area exceeding 2000 m2 g−1 with a total pore of 1.2 cm3 g−1. Doehlert experimental design was employed to evaluate the influence of adsorption process factors (adsorbent amount, pH, and temperature) on Cr (VI) removal by the three biochars. All three models present good correlation coefficient R2 greater than 0.975. The optimum conditions were at pH 2.54, temperature of 36.83 °C and an amount of 9 mg for orange biochar. For both biochars derived from pomegranate and watermelon, the optimal conditions were at pH 1.5, temperature of 22 °C and an amount of 10 mg. The kinetic results showed good correlation with pseudo-first-order model for orange and watermelon biochars, while the pseudo-second-order fits the data for pomegranate biochar. Maximum Langmuir adsorption capacities of hexavalent chromium were found to be 53.38 mg g−1, 73.01 mg g−1, 64.21 mg g−1, for orange, pomegranate, and watermelon biochars, respectively. [ABSTRACT FROM AUTHOR]

This work describes the effect of nitrogen and oxygen functional groups on the sorption properties of activated carbons produced from furfuryl alcohol. The poly(furfuryl) alcohol underwent carbonization in nitrogen, ammonia, and ammonia and air (in a 3:2 proportion) atmospheres at 600 °C for 4 h. The resulting materials were subsequently activated in a carbon dioxide atmosphere for 1 h at temperatures of 700 °C, 800 °C, 900 °C, and 1000 °C. The X-ray photoelectron spectroscopy (XPS) findings suggest that ammoxidation is superior to amination in terms of nitrogen doping. The maximum nitrogen concentration achieved after ammoxidation was 25 at.%, which decreased to 4 at.% after activation. Additionally, it was observed that oxygen functional groups have a greater impact on porous structure development compared to nitrogen functional groups. The materials activated through carbonization under an ammonia/air atmosphere attained the highest oxygen concentration of roughly 19 at.% as confirmed by XPS. The materials were evaluated for their sorption capacities for carbon dioxide and ethylene, which were 2.2 mmol/g and 2.9 mmol/g, respectively, at 30 °C. [ABSTRACT FROM AUTHOR]

In this study, the effects of artificial neural networks on CO2 adsorption on several types of rice husk activated carbon samples are investigated. Using conventional approach, the eight activated carbon samples are examined for carbon dioxide adsorption at 298 K and up to 1 bar pressure. The influence of altered training/validating ratios, various data initiation points, various training algorithms and number of neurons necessary for an artificial neural network model were investigated using ANN modelling. The work can give useful information on the effects of each of the investigated factors, which are crucial in ANN modelling and training techniques. The results may be used to create an optimum activated carbon, improved applications of gas and oil purification that plan to use artificial intelligence modelling in their evaluations. [ABSTRACT FROM AUTHOR]

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO2, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm's titration method, and pHpzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (qm exp) of MB and MG (349 mg g−1 and 274 mg g−1, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents. [ABSTRACT FROM AUTHOR]

Activated carbons obtained via the thermochemical treatment of lemon balm and mint herbs were applied for ionic polymers adsorption, which directly affects the stability of these types of aqueous suspensions. The examined carbonaceous materials were characterized by well-developed specific surface area (approximately 1000 m2/g) and mesoporous structure. The adsorbed amounts of anionic poly(acrylic acid) and cationic polyethyleneimine from one-component solutions reached significant levels, but the efficiency of adsorption of these compounds from binary solutions slightly decreased. Moreover, the ionic polymers showed stabilizing properties towards the activated carbons suspensions. For both adsorbents, the most stable suspensions were systems containing both types of polymeric macromolecules with different ionic characters. This was due to the occurrence of electrosteric and depletion stabilization mechanisms. Furthermore, the zeta potential and size of particle aggregates were also influenced by the presence of polymers in the aqueous suspensions of activated carbons. [ABSTRACT FROM AUTHOR]

Activated carbons exhibit a high grade of porosity, which together with structural stability, regenerability and cyclability makes them capable of achieving excellent hydrogen adsorption capacity. A further advantage comes from the ease of production and the use of recyclable and biocompatible materials. A simple way to produce activated carbons from amorphous cellulose involves procedures in which a pyrolysis process is combined with physical activation in CO 2. We used this approach by optimizing the production process tuning the activation times. The aim is to evaluate the influence of this process parameter on the formation of the specific surface area, the pore volume and fraction of micropores with a typical size <2 nm. The influence of these structural parameters on the hydrogen adsorption properties was then evaluated. The textural and adsorption characteristics were investigated using a commercial volumetric apparatus (ASAP 2460, Micromeritics) at −196 °C and pressures between 0 and 1 bar, while the morphological properties were investigated using scanning electron microscopy. The results show that the nanostructured samples are characterized by a very high degree of ultra-microporosity (<0.7 nm) with an average pore size between 0.5 and 0.6 nm and a high specific surface area, reaching maximum values around 1500 m2/g and micropore volume up to 0.58 cc/g. These morphological characteristics strongly influence the hydrogen adsorption properties, where the molecules adsorbed reach values very close to the coverage of ideal monolayer. The synthesized activated carbon samples show a higher hydrogen adsorption capacity than similar commercial materials tested under the same thermodynamic conditions. [Display omitted] • Easily tuning of ultra-microporosity. • Precursor influence on storage performance. • Hierarchical porous carbons and possibility hydrogen storage at low pressure. • Fully reversible hydrogen physisorption. • Amorphous cellulose as sustainable solution. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) from coconut shell, iron‐based metal organic framework (Fe‐MOF), zinc oxide (ZnO), and calcium oxide (CaO) were prepared as adsorbents for the CO2 adsorption process. The adsorption experiments were performed in a self‐designed fixed‐bed small reactor to study the influence of reaction conditions on the CO2 adsorption capacity of adsorbents. According to the findings, Fe‐MOF showed better performance in CO2 adsorption compared to the other selected adsorbents. The results were supported by the high surface area of Fe‐MOF, which was greater than that of AC, ZnO, and CaO. The optimal parameters for CO2 adsorption of all adsorbents were determined in terms of adsorbent dosage, operating pressure, and CO2 adsorption time. [ABSTRACT FROM AUTHOR]

Natural gas consisting mainly of methane is becoming increasingly prominent as a clean energy source. However, the major impurity, carbon dioxide, can adversely affect the performance of natural gas. Therefore, separating CO2 from CH4 is necessary to decrease the erosion of pipelines and increase the calorific value. This paper aimed at reviewing the performances, mechanisms, and novel developments of common adsorbents to adsorb pure CH4, pure CO2, and their mixtures. Several studies suggest that zeolites exhibit better separating performance than metal organic frameworks (MOFs) except the modified amine‐MIL group. Activated carbons may not be suitable adsorbents due to low selectivity between CO2 and CH4. The modified amine‐MIL group are the best type of adsorbent to separate CO2 from CH4 and its best operating conditions are at low pressure (<2 bar), low feed composition of CO2, and near room temperature using pressure swing adsorption (PSA) method. [ABSTRACT FROM AUTHOR]

With the increase in agriculture intensity, associated with the use of nitrogen-based fertilizers, nitrate pollution is starting to be an issue in soils and waters. Therefore, there is a need to find a way to prevent nitrate from leaching from the soils by retaining it into the soil. One of the solutions is to use carbon-based amendments such as activated carbon, which has a good sorption capacity. This study aimed at evaluating the sorption capacities of several activated carbons towards nitrate, and study the effects of different parameters, i.e. initial nitrate concentration, initial solution pH, contact time and co-existing anions, on their sorption capacities. Results showed that among eight tested activated carbons, from different feedstocks, four (L27, 2 K, 5 K, CS) presented a high sorption capacity, between 5.91 and 14.55 mg.g−1, which was affected (p < 0.001) by contact time (maximum sorption occurred within 60 min), solution pH (maximum sorption at pH 2) and the presence of co-existing anions. Moreover, the construction of sorption isotherms showed that sorption occurred mainly through monolayer, while the kinetic model showed a chemical sorption mechanism. Finally, infra-red analysis of the activated carbons revealed that various functional groups were involved in the sorption but also that electrostatic interaction was not the only sorption mechanism. This study demonstrates the importance of feedstock and activation type, as well as particular properties of activated carbon for the sorption of nitrate. It also shows the potential of four materials (L27,2 K, 5 K, CS) for the retention of nitrate in water-soil systems. [ABSTRACT FROM AUTHOR]

Gasification residues/chars (GR) and activated carbon (AC) are added to wastewater treatment processes mainly as a fourth purification stage, e.g., to adsorb heavy metals or pharmaceutical residues. However, the effects of GR or AC, which are transferred to the anaerobic digestion (AD) via the sludge, are not yet fully understood. Although, the positive effect of char addition on AD has been demonstrated in several investigations, systematic studies with chemically well described chars are still missing. Therefore, in this study, different chars were characterized in detail, subjected to AD in different concentrations, and their effect on methane production investigated. GR of a gasification plant with a floating fixed bed technology, carbon made by chemical impregnation with ZnCl2 from waste-wood, carbon produced by thermochemical activation with CO2 from GR and commercial powdered AC were used for the experiments. Among others, thermogravimetric analysis, physisorption, pH, and conductivity analysis were used to characterize the chars. Mesophilic AD batch tests with different concentrations (0.025, 0.05, 0.5, 1.0, 7.0, 14.0 gL−1) of all chars (GR and ACs, respectively) were performed with digester sludge from a wastewater treatment plant for a period of 47 d. Volatile fatty acids (VFA) as well as biogas production and CH4 concentrations were monitored. It could be shown, that concentrations below 1.0 g char L−1 did not result in significant effects on CH4 and/or VFA production, whereas high concentrations of GR and AC influenced both, the CH4 yield and kinetics. Depending on the production process and the characteristics of the chars, the effect on AD varied, whereby both, positive and negative effects on biogas yield and methane production were observed. This study provides the first systematic evaluation of char application to AD processes, and therefore allows for better predictions of char applicability and effect.

Activated carbons are commonly used for adsorption/depollution applications, but only a few studies are related to their lubricating properties. In order to investigate a new family of friction reducers, the tribological properties of biochars and derived activated carbons obtained from sugar cane bagasse are investigated. Activated carbons are obtained from either a physical (steam water) or chemical (with phosphoric acid) activation process. The tribological tests show that the activated carbons present very low friction coefficients, close to 0.08. The correlation of textural and tribological investigations shows that the specific surface area of the compounds as well as the microporous and mesoporous domain extensions are key parameters to optimize the friction reduction properties of activated carbons. The friction properties of the compounds are improved if the mesoporous domain extension is above 40% of the total porous volume. This study shows that local biomass waste valorization is possible and that sugar cane bagasse-derived activated carbons appear as interesting new friction reduction additives for lubricants.

Access to clean water remains a challenge in many parts of Africa. This is compounded by the increasing pollution levels with increasing population and industrialization. Activated carbon remains the most widely used adsorbent for the removal of chemical pollutants in both drinking water and wastewater treatment processes due to its unique chemical properties and a plethora of precursor materials for development. However, to date, no available literature has systematically summarized the advances in Africa on the adsorptive removal of contaminants using activated carbons and research issues such as data acquisition and presentation, analysis approaches, citations, inconsistencies and adsorption experimental setups remain largely undocumented. In this paper, adsorption studies from Africa focusing on activated carbons for the removal of various contaminants are reviewed, from 2007 to 2022. The study focused on a literature-based approach by searching key terms in selected databases. The adsorption data were mostly best described by the Langmuir and pseudo-second-order models for dyes, anions, metal ions pesticides, and pharmaceutical compounds. According to the pooled data, the highest adsorption capacity was 1552.5 mg g − 1 for PFOS adsorbed onto H3PO4-activated maize tassel-based carbon. The majority of the studies relied on linearized adsorption isotherm and kinetic models with coefficient of determination (R2) as the sole criterion for determining best-fitting models. Additionally, the majority of the studies are batch mode and laboratory-scale studies with no desorption and recyclability evaluations. Researchers should be careful to present accurate equations and units of parameters with proper citations. Pilot-scale and life cycle assessment (LCA) of the reported new materials represent an aspect largely unexplored. The fact that studies from most African countries, dating beyond 2007, could be obtained implies that activated carbons present an accessible and possibly sustainable technology for emerging economies.

The development of coal-based activated carbon for supercapacitors provides a robust and effective approach toward the clean and efficient use of coal, and it also offers high-quality and low-cost raw materials for energy storage devices. However, the one-step activation method for preparing coal-based activated carbon has problems, such as difficulty in introducing surface-functional groups and high KOH dosage. In our work, activated carbon was prepared through an effective strategy of oxidation and KOH activation with a low KOH content by employing coal-based carbon dots as raw material. The influence of temperature during the KOH activation of carbon dots on a specific surface area, pore structure, and various quantities and types of surface-functional groups, as well as on the electrochemical performance of supercapacitors, was systematically studied. The as-prepared sample, with the alkali–carbon ratio of 0.75, processes a large specific surface area (1207 m2 g−1) and abundant surface-functional groups, which may provide enormous active sites and high wettability, thus bringing in high specific capacitance and boosted electrochemical performances. The oxygen and nitrogen content of the activated carbon decreases while the carbon content increases, and the activation temperature also increases. The as-prepared activated carbon reaches the highest specific capacitance of 202.2 F g−1 in a 6 M KOH electrolyte at a current density of 10 A g−1. This study provides new insight into the design of high-performance activated carbon and new avenues for the application of coal-based carbon dots. [ABSTRACT FROM AUTHOR]

Pyrolysis and activation processes are important pathways to utilize residues after lipid extraction from microalgae in a high-value way. The obtained microalgae-based nitrogen-doped activated carbon has excellent electrochemical performance. It has the advantage of nitrogen self-doping using high elemental nitrogen in microalgae. In this study, two kinds of microalgae, Nanochloropsis and Chlorella, were used as feedstock for lipid extraction. The microalgae residue was firstly pyrolyzed at 500 °C to obtain biochar. Then, nitrogen-doped activated carbons were synthesized at an activation temperature of 700–900 °C with different ratios of biochar and KOH (1:1, 1:2, and 1:4). The obtained carbon materials presented rich nitrogen functional groups, including quaternary-N, pyridine-N-oxide, pyrrolic-N, and pyridinic-N. The nitrogen content of microalgae-based activated carbon material was up to 2.62%. The obtained materials had a specific surface area of up to 3186 m2/g and a pore volume in the range of 0.78–1.54 cm3/g. The microporous pore sizes of these materials were distributed at around 0.4 nm. Through electrochemical testing such as cyclic voltammetry and galvanostatic charge–discharge of materials, the materials exhibited good reversibility and high charge–discharge efficiency. The sample, sourced from microalgae Chlorella residue at activation conditions of 700 °C and biochar/KOH = 1:4, exhibited excellent endurance of 94.1% over 5000 cycles at 2 A/g. Its high specific capacitance was 432 F/g at 1 A/g. [ABSTRACT FROM AUTHOR]

In this work, the activated carbon of palm trunk fiber was prepared by the thermochemical activation method for the adsorptive removal of azo dyes known for their toxicity, including methylene blue (MB) and methyl orange (MO) from aqueous solution. This preparation was realized with activated factor phosphoric acid H3PO4 at 450°C in different impregnation ratios, which varied within the following range: 30, 60, 100, and 150 wt.%. Investigated adsorbents were characterized using several methods such as X-ray diffraction, N2 sorption, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and scanning electron microscopy techniques. Also, Boehm titrations and point of zero charge measurements were carried out to give more explication about surface properties. The effect of adsorbent dosage was evaluated and discussed. The results show that the adsorption capacity increases with increasing the mesoporous of the activated carbons. At 150 wt.% H3PO4 ratios were found to be appropriate for efficient adsorption of the (MO) dye (~862 mg·g-1) and (MB) dye (~508 mg·g-1). Isotherm data were investigated according to Langmuir and Freundlich equations. The obtained results revealed that the Langmuir model provides the best fit for the cationic MB dye while the Langmuir and Freundlich models offer the best fit for anionic MO dye. [ABSTRACT FROM AUTHOR]

Growing volatile organic compound (VOC) emission will cause air pollution and further threaten human health. Activated carbon is widely applied to treatment of VOCs in virtue of lower cost and excellent adsorption ability. In this work, the adsorption capacity of polarity VOCs on activated carbon is improved by oxalic acid (H2C2O4) hydrothermal modification. After 2 M H2C2O4 modification, the adsorption capacity of 2-butanone rose from 312.60 to 345.98 mg/g, and the time reaching saturation adsorption became shorter. BET results showed that both the specific surface area and total pore volume of 2 M H2C2O4-modified activated carbon increased by 3.32% and 3.9%, respectively. Both FTIR and XPS characterization confirmed variation of the surface oxygen–containing functional groups (SOFGs), while quantitative analysis via Boehm titration showed the significant increase of total acidity (61.36%), particularly the carboxyl content increased by 96.28%. The results indicated modification process can not only change the pore structure but also the SOFGs of activated carbons. The dynamic adsorption curves conform to the Bangham kinetics model, indicating that the adsorption of 2-butanone on both activated carbon is controlled by the diffusion in the pore channel. The adsorption data was also modeled by the internal particle diffusion model, and the internal diffusion adsorption stage is the rate-controlling step. The stability before and after adsorption and the cycling performance were studied. [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]

The main objective of this study was to assess the usefulness of the low-quality brown coal, ash obtained as a result of its combustion, as well as used gear oil for the production of mineral-carbon adsorbents. The adsorbents were characterized in terms of textural parameters, acidic-basic character of the surface, mineral matter contribution to the structure, as well as their suitability for drinking water purification. Adsorption tests were carried out against two synthetic dyes—methylene blue and methyl orange. In order to understand the nature of the organic pollutants adsorption, the effect of the initial dye concentration, temperature, and pH of the system as well as the phase contact time were investigated. The obtained mineral-carbon composite and activated carbons significantly differed not only in terms of the elemental composition and chemical character of the surface (from slightly acidic to strongly alkaline), but also showed a very diverse degree of specific surface development (from 21 to 656 m2/g) and the type of porous structure generated (from micro/mesoporous to typically mesoporous). Adsorption tests showed that the efficiency of organic dye removal from aqueous solutions primarily depends on the type of the adsorbent and adsorbate applied, and, to a lesser extent, on the temperature and pH of the system. In turn, kinetic studies have shown that the sorption of dyes on such materials is consistent with a pseudo-second-order kinetics model, regardless of the type of adsorbed dye. [ABSTRACT FROM AUTHOR]

CO2 capture is a practical approach to mitigating the impacts of global warming. Adsorption‐based carbon capture is a clean and potentially energy‐efficient method whose performance greatly depends on adsorbent design. In this study, we explored the use of jute‐derived carbon as a high‐performance adsorbent for CO2 capture. The carbons were produced by pyrolyzing powdered jute sticks with NaHCO3 as an activating agent at 500–700 °C. Impressive adsorption capacities of up to 2.5 mmol ⋅ g−1 and CO2/N2 selectivities of up to 54 were achieved by adjusting the pore size distribution and surface functionalization. Based on the isotherm results, the working capacities, regenerabilities, and potentials for CO2 separation were determined for a practical vacuum swing adsorption process. The adsorbent materials were characterized by XRD, FTIR, Raman, FESEM and N2 sorption at 77 K. This study provides a general approach for designing adsorbents for various gas‐separation applications. [ABSTRACT FROM AUTHOR]