Mesoporous Activated Carbons Research Articles

Facile synthesis of mesoporous active carbon from the valorisation of biomass waste and assessment of sequester efficiency of arsenic (As) from water

In this study, Phoenix dactylifera frond active carbons (PDFACs) were prepared using a low-cost biomass source through zinc chloride (ZnCl2) activation for the efficient elimination at batch scale, of the environmentally hazardous component arsenic (As) from polluted water. The influence of different factors including activation temperature, impregnation ratio, and impregnation time on the pore volumes, surface areas, and carbon yields of PDFACs were investigated. The PDF, PDF charcoal (PDFC) and PDFACs were characterized through thermogravimetric analysis (TGA), BET surface area (N2 adsorption-desorption), pore size distributions (PSD), SEM, FTIR, Energy-dispersive X-ray spectroscopy (EDX), and Transmission electron microscopy (TEM) analysis demonstrated successful modification in porosity and surface morphology. The maximum BET surface area of 1677 m2/g (1666 m2/g mesopore, 11 m2/g micropore surface area) and 0.665 cm3/g total pore volume were achieved at optimum synthesis condition of 4:5 impregnation ratio, 400 °C activation temperature, and 24 h soaking time. The impregnating ratio, impregnation time and activating temperature were found to have an inverse relationship with the yield of PDFACs. The impact of pH, sorbent dosage, As(V) concentration, contact time, temperature and agitation speed were inspected in batch experiments for As(V) adsorption efficiency by PDFAC. A maximum extraction efficiency 97% of As(V) was attained at optimal working conditions of 1.5 g dosage of PDFAC, initial concentration of As(V) 10 mg L−1, 120 min contact time, pH 6.0 and agitation speed 200 rpm at temperature 25 °C. The adsorption kinetic data fit the pseudo second order kinetic model well and the sorption data fit both Langmuir and Freundlich equations with little deviation in the r2 values. Research indicated that PDFAC derived from biomass wastes by ZnCl2 activation was found to be promising and feasible material for the elimination of As(V) from the aquatic environment.

Assessment of Two Materials as Adsorbents for the Effective Removal and Further Pre-Concentration of Gallium from Aqueous Solutions: Mesoporous Carbon vs. Clinoptilolite

In this research, the adsorption of gallium onto natural zeolite (clinoptilolite) and two mesoporous-activated carbons were compared and evaluated. The clinoptilolite was treated with HCl (HCPL), while mesoporous-activated carbons (MCSG60A and MCO1) were synthesized by replica method, using sucrose as the carbon precursor and silica gel as the template. These carbonaceous materials showed large pore sizes and mesoporous surface, as well as a suitable surface chemistry for cation adsorption, which promotes a high negative charge density. On the other hand, zeolites have narrower pore sizes, which hinders the material diffusion inside the particle; however, its strength is their ion exchange capacity. Regarding the gallium kinetic studies, it is described by Pseudo-second order model for both sorts of adsorbents. MCO1 is the best carbonaceous adsorbent studied, with a capacity of 4.58 mg/g. As for zeolites, between the two zeolites studied, HCPL showed the best results, with a gallium adsorption capacity of 3.1 mg/g. The gallium adsorption mechanism onto MCO1 material is based on physisorption, while HCPL is mainly retained due to an ion-exchange process. Regarding the Giles classification, MCO1 isotherm described an H-4 pattern of high affinity and characteristic of multilayer adsorption. The Double-Langmuir model fits properly within these experimental results. In the case of zeolites, HCPL adsorption isotherm followed an L-2 pattern, typical of monolayer adsorption—the Sips model is the one that better describes the adsorption of gallium onto the zeolite.

Reutilization of waste biomass from sugarcane bagasse and orange peel to obtain carbon foams: Applications in the metal ions removal

The high levels of heavy metals contained in residual water and the pollution generated by a large amount of unexploited agro-industrial waste are a serious problem for the environment and mankind. Therefore, in the present work, with the aim of treating and reducing the pollution caused by heavy metal ions (Pb, Cd, Zn and Cu), activated carbons (ACs) were synthesized from sugarcane bagasse (SCB) and orange peel (OP) by means of physical - chemical activation method in an acid medium (H3PO4, 85 wt%) followed by an activation at high temperature (500 and 700 °C). Thereafter, these materials were used to produce carbon foams (CF) by the replica method and to evaluate their adsorbent capacity for the removal of heavy metals from synthetic water. XRD, FTIR, DLS, BET, Zeta Potential (ζ), SEM-EDS and AAS were used to investigate their structures, surface area, pore size, morphology, and adsorption capacity. The results show that as-prepared CF have a second level mesoporous structure and AC present a micro-mesoporous structure with a pore diameter between 3 and 4 nm. The experimental adsorption capacities of heavy metals showed that the CF from OP present a better elimination of heavy metals compared to the AC; exhibiting a removal capacity of 95.2 ± 3.96% (Pb) and 94.7 ± 4.88% (Cu) at pH = 5. The adsorption values showed that the optimal parameters to reach a high metal removal are pH values above 5. In the best of cases, the minimum remaining concentration of lead and copper were 2.4 and 2.6 mg L−1, respectively. The experimental data for carbon adsorbents are in accordance with the Langmuir and BET isotherms, with R2 = 0.99 and the maximum homogenous biosorption capacity for lead and copper was Qmax = 968.72 and 754.14 mg g−1, respectively. This study showed that agro-industrial wastes can be effectively retrieved to produce adsorbents materials for wastewater treatment applications.

The Use of High Surface Area Mesoporous-Activated Carbon from Longan Seed Biomass for Increasing Capacity and Kinetics of Methylene Blue Adsorption from Aqueous Solution.

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO2 under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m2/g and mesopore volume of 0.474 cm3/g which accounts for 44.1% of the total pore volume. These activated carbons were utilized as porous adsorbents for the removal of methylene blue (MB) from an aqueous solution and their effectiveness was evaluated for both the adsorption kinetics and capacity. The adsorption kinetic data of MB were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the pore-diffusion model equations. It was found that the adsorption kinetic behavior for all carbons tested was best described by the pseudo-second-order model. The effective pore diffusivity (De) derived from the pore-diffusion model had the values of 4.657 × 10−7–6.014 × 10−7 cm2/s and 4.668 × 10−7–19.920 × 10−7 cm2/s for the microporous- and mesoporous-activated carbons, respectively. Three well-known adsorption models, namely the Langmuir, Freundlich and Redlich–Peterson equations were tested with the experimental MB adsorption isotherms, and the results showed that the Redlich–Peterson model provided the overall best fitting of the isotherm data. In addition, the maximum capacity for MB adsorption of 1000 mg/g was achieved with the mesoporous carbon having the largest surface area and pore volume. The initial pH of MB solution had virtually no effect on the adsorption capacity and removal efficiency of the methylene blue dye. Increasing temperature over the range from 35 to 55 °C increased the adsorption of methylene blue, presumably caused by the increase in the diffusion rate of methylene blue to the adsorption sites that could promote the interaction frequency between the adsorbent surface and the adsorbate molecules. Overall, the high surface area mesoporous carbon was superior to the microporous carbon in view of the adsorption kinetics and capacity, when both carbons were used for the removal of MB from an aqueous solution.

Kinetic study of adsorption carboxylic acids of used cooking oil using mesoporous active carbon

This study investigates the reduction of free fatty acids from the problem of used cooking oil in the food industry with bio-waste adsorbents such as banana peels—experimental conditions at the activation temperature of making activated carbon. Adsorption kinetics and temperature of activated effects were studied. Bio-char activated at 600, 650, and 700°C. The used cooking oil and activated carbon were analyzed using Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray energy-dispersive, and BET analysis. Activated carbon has a surface area of 548 m2/g, with an average pore diameter of 35 nm (range of mesophore). As a result, bio-char activated at 700°C is best presented by a linear pseudo-second-order kinetic model suitable for describing the adsorption kinetic. The maximum adsorption capacity was 62 mg/g at 303 K. Carboxylic groups as free fatty acid was removed from used cooking oil used surface of activated carbon. Models best described the experimental data as with the higher values of the correlation coefficient (R2). The results of this study prove that the banana peel bio-waste ingredient, which is food waste, is a potential adsorbent to reduce free fatty acid levels to the standard of 0.3

Mesoporous Activated Carbon Supported Ru Catalysts to Efficiently Convert Cellulose into Sorbitol by Hydrolytic Hydrogenation

Catalysts consisting of Ru nanoparticles (1 wt%), supported on mesoporous activated carbons (ACs), were prepared and used in the one-pot hydrolytic hydrogenation of cellulose to obtain sorbitol. The carbon materials used as supports are a pristine commercial mesoporous AC (named SA), and two samples derived from it by sulfonation or oxidation treatments (named SASu and SAS, respectively). The catalysts have been thoroughly characterized regarding both surface chemistry and porosity, as well as Ru electronic state and particle size. The amount and type of surface functional groups in the carbon materials becomes modified as a result of the Ru incorporation process, while a high mesopore volume is preserved upon functionalization and Ru incorporation. The prepared catalysts have shown to be very active, with cellulose conversion close to 50% and selectivity to sorbitol above 75%. The support functionalization does not lead to an improvement of the catalysts’ behavior and, in fact, the Ru/SA catalyst is the most effective one, with about 50% yield to sorbitol, and a very low generation of by-products.

Sludge‐based mesoporous activated carbon: the effect of hydrothermal pretreatment on material preparation and adsorption of bisphenol A

AbstractBackgroundThe excess sludge produced by sewage treatment plants contains a large number of pollutants, which is of huge environmental risk. Transforming this kind of solid waste into adsorption materials is an effective approach to realize the resource utilization of sludge. Combined with hydrothermal pretreatment and chemical activation, the synthesis of sludge‐based mesoporous carbon is used to remove bisphenol A (BPA) in wastewater.ResultsA resource recycling measure to prepare mesoporous activated carbons (MACs) from sewage sludge was developed via the combination of hydrothermal pretreatment and chemical activation using sewage sludge and sulfuric acid as carbon precursor and activating agent, respectively. The combination of hydrothermal pretreatment and chemical activation not only can make efficient use of the activating agents but also facilitate the deep pyrolysis of the sludge. The resultant MAC obtained using the hydrothermal pretreatment possessed a larger total surface area, less crystalline phase and a narrower pore size distribution compared to other samples. Meanwhile, the MAC obtained from hydrothermal pretreatment presented the highest amount of adsorption of BPA and achieved a better capture than the reference commercial activated carbons. In addition, a possible adsorption mechanism has been proposed to further analyze the enhanced adsorption performance.ConclusionsThe yield and mesoporous content of the obtained MAC is 59.19% and 31.51%, respectively. The maximum adsorption capacity for BPA is 137.87 mg g−1. Microporosity, hydrogen bonding and π–π effect introduced by the hydrothermal pretreatment play an important role in BPA adsorption. © 2020 Society of Chemical Industry

Influence of dissolved organic matter and activated carbon pore characteristics on organic micropollutant desorption

By simulating decreasing inflow concentrations, the extent of desorption of organic micropollutants (OMP) from three activated carbons (AC) was examined in laboratory batch tests. The tested AC showed strong differences in pore size distribution and could therefore be characterized as typical micro-, meso- and macroporous AC, respectively. Adsorption and desorption conditions were varied by using drinking water (containing dissolved organic matter (DOM)) and DOM-free pure water as background solutions to examine the influence of DOM on OMP desorption for the different AC. Under ideal conditions (adsorption and desorption in pure water) adsorption of the tested OMP was found to be highly up to completely reversible for all tested AC. Under real conditions (adsorption and desorption in drinking water) additional DOM adsorption affects desorption in different ways depending on the AC pore structure. For the micro- and mesoporous AC, an increased irreversibility of OMP adsorption was found, which shows that DOM adsorption prevents OMP desorption. This could be referred to pore blockage effects that occur during the parallel adsorption of DOM and OMP. For the macroporous AC, DOM adsorption led to an enhanced OMP desorption which could be attributed to displacement processes. These results show that smaller pores tend to be blocked by DOM which hinders OMP from desorption. The overall larger pores of the macroporous AC do not get blocked which could allow (i) OMP to desorb and (ii) DOM to enter and displace OMP.

Electrochemical performance of microporous and mesoporous activated carbons in neat and diluted 1-ethyl-3-methylimidazolium tetrafluoroborate

Abstract 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIm·BF4), neat and diluted with propylene carbonate to 1 mol L−1, have been employed as electrolytes of electrical double-layer capacitors (EDLCs). The effects of microporosity and mesoporosity in activated carbon (AC) electrodes on the capacitive and resistive performances upon the use of neat and diluted EMIm·BF4 have been explored. In addition to cyclic voltammetry and galvanostatic charge–discharge tests, electrochemical impedance spectroscopy has been performed employing Kang's equivalent circuit model consisting of three resistances, three constant phase elements, and one bounded Warburg impedance. The overall impedance of the EDLC cell was separated into components of intrinsic resistance, bulk electrolyte, diffusion layer, and Helmholtz layer. The specific capacitance and the equivalent series resistance (ESR) of mesoporous AC were found to be highly dependent on the rate of ionic transfer. Lower cell voltage was identified as being responsible for lower specific capacitance and larger ESR of mesoporous AC, which was similarly seen in the neat and diluted EMIm·BF4, and could be alleviated by increasing the cell voltage. The inferior rate performance and the cell-voltage-dependent performance of mesoporous AC, which were more distinctly observed in the neat EMIm·BF4, could be attributed to the lower mobility of EMIm+ and BF4− in mesopores.

Electrochemical performance of activated carbons prepared from rice husk in different types of non-aqueous electrolytes

Activated carbons (ACs) prepared from rice husk (RH), an agricultural byproduct, have mesoporosity that is obtainable from leaching of the mineral component of silica. To verify the suitability of RH-derived ACs for the use of electrode materials of electrical double-layer capacitors, we evaluated the electrochemical performance of three RH-derived ACs (two micro- and mesoporous ACs and one mesoporous AC). Evaluation was done by using the non-aqueous ionic electrolyte solutions 1 mol dm−3 triethylmethyl ammonium tetrafluoroborate/propylene carbonate (PC) solution, 1.5 mol dm−3 spiro-(1,1′)-bipyrrolidinium tetrafluoroborate/PC (SBP·BF4/PC) solution, and the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm·BF4). Under low voltage scan rate (1 mV s−1) and low current density (<1 mA cm−2), mesoporous AC, which had the highest specific surface area, showed the highest specific capacitance (120 F g−1) in EMIm·BF4. However, its specific capacitance considerably decreased because of the increase in scan rate and current density. Under high scan rate (10 and 100 mV s−1) and high current density (>10 mA cm−2), micro- and mesoporous AC in 1.5 mol dm−3 SBP·BF4/PC showed the highest specific capacitance and highest retention of specific capacitance, even though its specific surface area was not the highest. Mesoporous AC showed voltage-dependent specific capacitance, indicating that ionic transport in the mesoporous structure was sensitive to electric field. It was finally shown that micro- and mesoporosity developed by utilizing natural structure and composition of RH was useful for the electrode materials of advanced electrical double-layer capacitors requiring more viscous non-aqueous electrolytes.

Lignite-derived high surface area mesoporous activated carbons for electrochemical capacitors

Mesoporous activated carbons (ACs) were successfully prepared from lignite using KOH as activation agent at the temperature above 700°C. The pore structure and surface chemistry of the as-prepared ACs were characterized by means of nitrogen adsorption–desorption, X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The results show that such prepared mesoporous ACs have a high specific surface area (~3036m2·g−1) with a hierarchical macro–meso–micro-pore structure and oxygen-enriched surface. The electrochemical performances of the ACs as electrode materials for electrochemical capacitors (ECs) were assessed by galvanostatic charge–discharge, cyclic voltammetry and cycling durability tests. It was demonstrated that the mesoporous ACs produced in this study possessed a maximum specific capacitance of 355F·g−1 and 196F·g−1 in 3M KOH aqueous and 1M (C2H5)4NBF4/PC organic electrolytes, respectively, at a current density of 50mA·g−1, and exhibited a desirable energy and power density with a superior cycling performance. The excellent capacitive behavior of the prepared mesoporous ACs in aqueous system is attributed to their unique macro–meso–micro-hierarchical pore structure with high surface area and oxygen-containing surface. Their superb electrochemical performance in the organic electrolyte is attributed to their well-developed mesoporous structure.

Mesoporous silicon oxycarbide materials for controlled drug delivery systems

The suitability of using mesoporous silicon oxycarbide materials as controlled drug delivery systems is reported here. The silicon oxycarbide materials are known for their nanostructured nature composed of silica and carbon nanodomains in an amorphous matrix. The SiOC present a large surface area and a bimodal porous structure with pores of 6 and 100nm size. The surface modification of the SiOC with amino-containing silanes leads to a similar porous structure with the grafted silane adopting a specific configuration depending on the amount of silane. The availability of the amino groups to interact with the loaded drug molecule has been determined through infrared spectroscopy whereas the amount of drug adsorbed on the material has been calculated through UV–vis spectroscopy and thermogravimetry. The materials are biologically inactive but they can host a large amount of active drug molecules per cm2 into their porous structure. The adsorption kinetics have been compared with mesoporous silica and mesoporous active carbon and we have deducted that the drug penetrates faster in the SiOC than in the AC and the adsorption mechanism occurs via acceptor–donor interactions between the drug molecules and the surface of the materials.

Remarkable effect of soft-templating synthesis procedure on catalytic properties of mesoporous carbon supported Ni in hydrodechlorination of trichloroethylene in liquid phase

Ordered mesoporous carbon (CST-A) obtained by soft-templating method under acidic condition was used for preparation of nickel containing catalyst by incipient wetness impregnation with an aqueous solution of NiCl2·6H2O. The reduction of as prepared catalysts by 10% H2/Ar at 673K led to formation of well dispersed active metallic phase with average nickel particles size ∼11nm. 2wt.% Ni/CST-A was examined as a catalyst in hydrodechlorination (HDC) of trichloroethylene in liquid phase, without presence of an additional organic solvent in the reaction mixture. Ethane and ethylene were the predominant product of reaction. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies for catalysts after reduction and after HDC reaction indicated that use of hydrophobic, mesoporous active carbon as the support for nickel led to formation of resistant for sintering and leaching catalyst and the effective material for catalytic removal of trichloroethylene from water. Post-reaction deposits investigated by the temperature programmed hydrogenation (TPH) showed substantial amounts of carbon-containing deposit, with C2-hydrocarbons desorbing at a relatively low temperature (∼650K).

Excellent performance for preferential CO oxidition over porous carbon supported IrFe catalysts.

By employing mesoporous carbon (MC), active carbon (AC), XC-72 and CMK-3 as the supports, we report carbon supported IrFe catalysts in the application of preferential oxidation of CO for the first time. The optimal activity was obtained over IrFe/MC, with a CO conversion of 83.5% at 80 degrees C. This activity became even better in the second run and achieved a CO conversion of 89.5% at 60 degrees C. The as-prepared catalysts have been characterized by N2 sorption isotherms, X-ray diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy, X-ray photoelectron spectroscopy and H2 temperature programmed reduction. The promising PROX performance over the IrFe/MC can be attributed to the intrinsic surface properties of MC and its specific interaction with metal species.

Effect of Pore Structure of Activated Carbon on its Electrochemical Performance in Non-Aqueous Electrolyte

The surface area and pore distribution of activated carbons (ACs) were characterized by nitrogen adsorption isotherms at 77 K, and double layer capacitors were assembled to demonstrate the electrochemical performance. With 1 mol·L-1 tetraethylammonium tetrafluoroborate dissolved in acetonitrile (Et4NBF4/AN) as electrolyte, electrochemical methods including cyclic voltammetry (CV) and galvanostatic charge-discharge tests were used to evaluate the capacitors. Results show that the surface area has a limited effect on the specific capacitance of ACs and the increaing of mesoporous content can decrease the capacitance decay rate at large discharge current. When current increases from 0.15A·g-1 to 9.6A·g-1, the minimum specific capacitance decay rate of mesoporous ACs is 10.93%, while that of the microporous ACs is 15.21%;the contributions of mesoporous surface area to the specific capacitance drop from 10.10 to 9.95μF·cm-2, while that of microporous surface area drop from 5.68 to 4.21μF·cm-2.

Mechanism of adsorption of different humic acid fractions on mesoporous activated carbons with basic surface characteristics

The effects of the humic acid (HA) nature and the activated carbon (AC) surface chemistry on the effectiveness of HA removal were investigated. Brown (BHA) and gray (GHA) humic acid fractions of different structure and physicochemical properties were tested in the adsorption process using mesoporous ACs. The modification of chemical structure and surface properties of AC was achieved by ammonization (AC/N) and hydrogen treatment (AC/H). Both approaches led to a decrease in the oxygen content followed by an increase in the carbon basicity, maintaining the porous texture of AC nearly unaltered. Over twice higher removal degree of BHA and GHA was observed for the modified ACs. The kinetics of adsorption of HA fractions have been discussed using the pseudo-second-order model and the intraparticle diffusion model. All ACs showed a higher adsorption capacity toward BHA compared to GHA, which is mainly attributed to the lower molecular weight of BHA. The shape of the equilibrium isotherms indicates a strong competition between water and HA molecules for adsorption sites of the carbon surface.

High Rate and Long Cycle Life Anodes Via ALD TiO2 Coatings on Mesoporous Activated Carbons

Titanium dioxide (TiO2), a candidate as anode active material for lithium ion batteries, has attracted much attention from researchers due to its safety characteristics arising from its high electrochemical potential (~1.5V) vs. Li/Li+, low cost, material availability and environmental benignity. However, low electric conductivity, sluggish Li+ diffusivity and poor cycle performance of TiO2 have limited its wide acceptance in practical rechargeable lithium ion batteries. Various strategies such as TiO2-C-nano metal composites [1], nanofibers [2], and TiO2 flakes [3], have been investigated in literature work. While these studies led to improved performance to various degrees, they were limited either in rate (<20C) or cycle life (<100 cycles) or both. A recent work [4] involved atomic layer deposition (ALD) of TiO2on graphene powders and demonstrated vastly improved rate and cycle capabilities of the resulting materials. Here we present an alternative and promising method of preparing extremely high rate and long cycle life anodes via ALD coatings of TiO2on mesoporous activated carbon (AC) electrodes. Figure 1 shows charge and discharge voltages between 1.5V and 3.0V (vs. Li/Li+) of an ALD TiO2-AC and a mesoporous AC baseline coin half cell versus specific capacity based on total active materials. Conventional carbonate-based lithium ion electrolyte was used. The ALD TiO2-AC cell demonstrated nearly five-fold capacity increase against the baseline with voltage profiles typical of nano TiO2. The contribution of ALD TiO2to the observed capacity is ~83%, which leads to ~73 mAh/g specific capacity. The relatively low specific capacity is because of the 1.5V cutoff voltage used in this study. Figure 2 shows rate performance of ALD TiO2-AC vs. AC baseline half cells. The ALD TiO2-AC demonstrated very high rate capability, e.g. delivering 70% of low rate capacity at 400C rate, surpassing that of AC baseline. Figure 3 shows excellent cycle stability of ALD TiO2-AC half cell with 80% capacity retention after 800 cycles. The remarkable electrochemical performance demonstrated from ALD TiO2-AC is attributed to ALD enabled TiO2nano structure. Such nano structure is responsible for facile lithium insertion/extraction leading to extremely high rate capability and long cycle life due to stress/stain free nano architecture. The results in this study suggest a promising material processing methodology for high rate and long cycle life anodes for lithium ion batteries used in applications that require fast rate capability, when implemented with high throughput, high volume ALD processes. Figure 1. Charge and discharge voltage profiles of ALD TiO2-AC/Li vs. AC/Li baseline half cells.Figure 2. Rate capability tests of ALD TiO2-AC/Li vs. AC baseline half cells.Figure 3. Cycle life test of an ALD TiO2-AC/Li cell. References Song Gyun Lee, Honggui Deng, Jun Hu, Lihui Zhou, Honglai Liu, Int. J. Electrochem. Sci., 8, 2204 (2013).Zunxian Yang, Guodong Du, Qing Meng, Zaiping Guo, Xuebin Yu, Zhixin Chen, Tailiang Guo, and Rong Zeng, J. Mater. Chem., 22, 5848 (2012).Ming-Che Yang, Yang-Yao Lee, Bo Xu, Kevin Powers, Ying Shirley Meng, J. Power Sources, 207, 166 (2012).Chunmei Ban, Ming Xie, Xiang Sun, Jonathan J Travis, Gongkai Wang, Hongtao Sun, Anne C Dillon, Jie Lian and Steven M George, Nanotechnology 24, 424002 (2013).

Fabrication, characterization and evaluation of mesoporous activated carbons from agricultural waste: Jerusalem artichoke stalk as an example

This work explores the feasibility of Jerusalem artichoke stem (JAS), an agricultural waste, as an alternative precursor for fabrication of mesoporous activated carbon (MAC) via conventional ZnCl2 activation. The as-prepared JAS-MACs were characterized by thermogravimetric, nitrogen gas adsorption isotherm and high resolution scanning electron microscopy analysis. The interacting effects of chemical dosage, activation temperature and time on the mesoporosity, mesopore volume and carbon yield were investigated, and further optimized by response surface methodology (RSM). The Brunauer-Emmett-Teller surface area, mesoporosity and mesopore volume of the JAS-MAC prepared under optimum condition were identified to be 1631 m(2)center dot g(-1), 90.16% and 1.11 cm(3)center dot g(-1), respectively. Compared with commercial activated carbons, this carbon exhibited a comparable monolayer adsorption capacity of 374.5 mg center dot g(-1) for Methylene Blue dye. The findings suggest that RSM could be an effective approach for optimizing the pore structure of fabricated activated carbons.

Enhanced removal of Cr (VI) from aqueous solution by mesoporous activated carbons

The capability of mesoporous activated carbons (MACs) to adsorb Cr (VI) in aqueous solution was investigated. The MACs were prepared in the lab from upgraded coal tar pitch using the nano-sized imprinting method. Adsorption of Cr (VI) was found to be dependent on the solution pH. The adsorption kinetic data was found to fit well with a pseudo-second-order rate equation. Three adsorption isotherm models were used to analyse the equilibrium data. Removal of Cr (VI) increased with an increase in mesoporosity of MACs, highlighting the importance of mesoporosity in enhancing adsorption efficiency. The major surface oxygen groups were carboxylic, lactonic and hydroxyl. X-ray photoelectron spectroscopy analysis was employed to investigate the sorption mechanism. It was revealed that a portion of Cr (VI) was adsorbed via electrostatic interaction, while the rest was adsorbed in the reduced form (Cr (III)) which was most likely bound to surface oxygen groups on the MAC.

Electrical double-layer capacitance of micro- and mesoporous activated carbon prepared from rice husk and beet sugar

To produce micro- and mesoporous RH-derived activated carbons (ACs), a mixture of rice husk (RH) and beet sugar (BS) was carbonized to produce a precursor, which was subjected to the silica-leaching process and then CO2 activation. The silica, intrinsically present in natural RH, was used as a template for mesopores, and BS was used for additional development of micropores. The RH-derived ACs were prepared with the intention of application as the electrode materials of electrical double-layer capacitors. The RH-derived AC, exhibiting BET specific surface area of 1357m2/g, total pore volume of 0.99mL/g, and mesopore volume fraction of 44.4%, showed superior capacitive performance in both aqueous (1M H2SO4) and organic (1M TEMA·BF4/PC) electrolytes, in comparison with commercial microporous and mesoporous ACs with similar BET specific surface area (1200–1600m2/g). The specific capacitance, evaluated by means of cyclic voltammetry using a three-electrode cell system at a scan rate of 5mV/s, was 106F/g for the aqueous electrolyte, and 114F/g for the organic electrolyte. Higher specific capacitance in the organic electrolyte was obtained from the RH-derived AC, and was much higher than those of commercial ACs. The good compatibility with both the aqueous and organic electrolytes was attributed to the well-balanced micro- and mesoporosity. The role of the microporosity and mesoporosity on the capacitive performance of ACs in both electrolytes is also discussed.