Effect Of Activation Conditions Research Articles

Optimizing Activated Carbon Production from Waste Cashew Nut Shell with Zinc Chloride: A Box-Behnken Design and Group Method of Data Handling (GMDH) Application

In this study, Response surface methodology (RSM) and innovative Group Method of Data Handling (GMDH) approaches are applied to investigate the optimal process conditions of zinc chloride activated cashew nut production process. The effects of activation conditions (i.e. activation temperature, activation time, and impregnation ratio) on the achievable BET surface areas were studied with the aid of Box Behnken Design (BBD) and GMDH. Comparative analyses of RSM and GMDH-type neural models were further researched. During the process, the polynomial model equations developed were modified and fine-tuned to predict the highest BET surface area(s) using regression analysis and GMDH multi-layered iterative algorithm (MIA). Analysis of Variance (ANOVA) revealed that the significant factor(s) were impregnation ratio, impregnation ratio product, and the 2-way interactions (activation temperature and impregnation ratio) for ZnCl2 activated cashew nut shell. The best activation conditions for producing highest BET surface area of 504 m2.g-1 was activation temperature (873K), activation time (60 min), and impregnation ratio (1.50).The proposed GMDH-type BET model was ascertained to be the best model with average correlation coefficient (R) and root mean square error (RMSE) of 0.925 and 32.0 respectively. Sensitivity analysis conducted for GMDH-type neural network also revealed that the activation temperature and activation time with sensitivity values of 90.6% and 74.1% respectively were the most influential parameters in the basic (ZnCl2) activation process. The results of this study show that RSM and GMDH-type neural network could be applied as effective analytical tools for optimizing the ZCNS (zinc chloride-activated cashew nut shells) manufacturing process.

Effects of Activation Conditions on the Characteristics, Adsorption Capacity, and Energy Sorage of Carbon Aerogel from Watermelon Rind

AbstractIn this work, a watermelon rind‐derived carbon aerogel (WRCA) was synthesized via a facile and green procedure including hydrothermal combined freeze‐drying and pyrolysis technique. The influences of pyrolysis conditions on the characteristics, adsorption capacity, and energy storage of the produced WRCA were thoroughly investigated under two distinctive pyrolysis conditions in N2 and CO2 media to obtain the corresponding WRCA‐N and WRCA‐C products, respectively, at different temperatures (600, 700, and 800 °C). As a result, WRCA‐N samples exhibited notable hydrophobicity with a wetting angle of 127°, showing excellent concordance with the adsorbent field. Furthermore, the maximum adsorption capacity of used coconut oil, hexane, butanol, and chloroform for WRCA‐N pyrolyzed at 800 °C (WRCA‐N800) reached 70.521, 53.506, 58.102, and 59.913 g/g, respectively, whilst the adsorption process also followed the pseudo‐first‐order kinetic model. On the other hand, WRCA‐C held up considerable hydrophilic traits and cannot be used to adsorb organic matters. Nonetheless, WRCA‐C activated at 600 °C (WRCA‐C600) indicated the best physicochemical properties and energy storage capacity with better specific capacitance (190 F/g) compared to WRCA‐N600 (31.40 F/g), thanks to its large specific surface area, high porosity (91.27 %), and higher hetero‐element O content (9.79%) than other samples. Additionally, the electrochemical characteristics of WRCA‐C600 electrode were alternatively confirmed using the 2‐electrode supercapacitor model, demonstrating a high energy density (26.38 Wh/kg) and power density (2374.50 W/kg). The obtained results demonstrate the promising applications of carbon aerogel synthesized from the watermelon rind in the adsorption and energy storage sectors.

Fast-pyrolysis lignin-biochar as an excellent precursor for high-performance capacitors

Lignin-based activated carbons (LAC) were produced using thermochemical pretreatment and chemical activation with KOH. Fast pyrolysis at 550 °C in a CO2/N2 atmosphere resulted in lignin char (LC) with a more developed porous structure than slow pyrolysis. The effect of activation conditions (KOH usage, temperature, and duration) on surface/physicochemical properties and electrochemical characteristics of the resulting LAC was fully studied. Using fast pyrolysis lignin char as a precursor and optimized activation conditions (wKOH:wLC = 2, 800 °C, and 2 h), the resulting LAC featured a large surface area of 2149.5 m2 g−1, a total pore volume of 0.88 m3 g−1, and high capacitance of 300 F g−1 at 0.5 A g−1 in a 6 mol L−1 KOH electrolyte. The LAC-based symmetric supercapacitor could offer superior energy density (19.15 W h kg−1 at 250 W kg−1 power density) and a stable lifetime (98.2% of original capacity after 10,000 charge-discharge cycles). The excellent capacitor performance of LAC was attributed to its microporous-mesoporous structure developed from fast pyrolysis and subsequent chemical activation.

Oxamic acid potassium salt as a novel and bifunctional activator for the preparation of N-doped carbonaceous CO2 adsorbents

N-doped porous carbons have shown great potential as CO2 adsorbents. In the current work, we proposed the use of oxamic acid potassium salt (OAPS) as a novel and bifunctional activator for direct synthesis of N-doped porous carbon. OAPS served as both chemical activator and nitrogen source at the same time. N-doped carbons were prepared from different biomass materials including cellulose, agar, and glucose. The yielded carbons exhibited micropores dominated porous structure. Effects of activation conditions and biomass types on the carbons’ physicochemical properties were thoroughly studied. As a result, the carbons showed high specific surface area (733–2438 m2/g) and nitrogen content (1.51–3.92 wt%). The presence of narrow micropores and doped nitrogen qualified OAPS activated carbons as efficient CO2 adsorbents. These carbons demonstrated high CO2 uptake of 3.91 mmol/g at 25 °C and 1 bar. Respective effects of narrow micropores and N-doping on CO2 adsorption were also analyzed and revealed. The current study indicated that OAPS could be used as a very convenient and versatile activator for the preparation of N-doped carbonaceous CO2 adsorbents.

Preparation of activated carbon from sewage sludge using green activator and its performance on dye wastewater treatment

ABSTRACT The remediation of dyes in wastewater using activated carbon produced from sewage sludge pyrolysis char (PYC) is an environmentally friendly and sustainable process. However, traditional activators can cause corrosion of the processing facility, thereby increasing the costs of waste disposal. Here, activated carbons were prepared from sewage sludge PYC, and the effects of activation conditions (different activators, temperature and time, and char:activator mass ratio) on their specific surface areas and adsorption of iodine and methylene blue (MB; model dye) were studied. The results showed that a value of 952 m2/g could be attained for the specific surface area and values of 882 and 162 mg/g for the adsorption of iodine and MB, respectively, by heating PYC with KHCO3 (PYC- KHCO3: 1:2 w/w) for 60 min at 800 ℃. Compared with activation by KOH, the adsorption of MB using PYC-KHCO3 was slightly lower but the yield was 13.7% higher. Optimization of the activation process using surface response modelling indicated that sensitivity of three key factors to the adsorption of iodine and MB followed the order: Mass ratio > temperature > time. Systematic investigation of the effects of time, pH and temperature on the removal of MB by the activated carbon revealed that adsorption conformed to the Langmuir model and pseudo-second-order kinetics. The proposed mechanisms of MB adsorption involved ion exchange, functional group complexation and physical/π-π interactions. This study provides a basis for the efficient remediation of dyes in wastewater using activated carbon prepared from sustainable sewage sludge PYC and green chemistry.

Effect of activation conditions and iron loading content on the catalytic cracking of toluene by biochar

Biochar (BC) is a catalyst carrier with a porous structure and low production cost. Herein, a Fe-loaded BC catalyst was prepared by impregnation and calcination, and use toluene to determine the removal efficiency of the catalyst. When the Fe impregnation solution mass fraction was 4%, the removal efficiency for the Fe-loaded BC catalyst was 94.1%. The amount of H2 produced by toluene catalysis is 963.22 ml, which is about three times the total amount of H2 produced by toluene self-pyrolysis and catalyst self-gasification. The effects of steam activation conditions and Fe impregnation mass fraction on the microstructure of BC were studied. The results show that the activation temperature and time can increase the BET surface area. A high concentration of steam volume and impregnation solution decreases the BET surface area. The characterizations of the catalyst before and after the toluene removal experiment shows that C–O bond plays a vital role in the removal process and micropores of BC preferentially adsorb toluene. The adsorption mechanism on BC mainly depends on n–π interaction and pore filling. The electrostatic attraction and π–π interaction on Fe-loaded BC were enhanced. Loading treatment introduces lattice oxygen and leads to increased oxygen vacancies.

Effects of Activation Conditions on the Structure and Capacitive Performance of Hollow Tubular Fibrous Brucite Templated Carbons

Effects of Activation Conditions on the Structure and Capacitive Performance of Hollow Tubular Fibrous Brucite Templated Carbons

Effects of Activation Conditions on the Properties of Sludge-Based Activated Coke

Sewage sludge and waste biomass are unavoidable byproducts of municipal and industrial processes. Both materials have significant carbon contents. Activated coke with a developed pore structure can be obtained after its physical activation. In this study, sewage sludge and waste poplar bark were used as precursor materials to prepare activated coke by steam, carbon dioxide gas, and their mixtures. The effects of different concentrations of activation gas on the activated coke product were investigated. Through nitrogen adsorption analysis, it was found that activated coke has a higher specific surface area and better pore structure when activated in gas containing 20% steam. The activated coke prepared by carbon dioxide gas activation has higher microporosity than that prepared by steam activation. Infrared spectrum analysis shows that steam activation is beneficial to the formation of free hydroxyl functional groups. Through scanning electron microscopy analysis, the pores of activated coke prepared by steam activation appeared to extend deeper in the structure of the coke, while the pores of activated coke prepared by carbon dioxide activation appeared to have fine circular structures. The activated coke prepared by the activation of mixed gas appeared to have ablated particles on the surface due to the ablation of the pore structure. In order to prepare activated coke with excellent adsorption performance, the physical and chemical properties of activated coke under different activation conditions were studied in detail.

Systematic study of dynamic CO2 adsorption on activated carbons derived from different biomass

In this work, biomass wastes (chestnut shells, walnut shells and macadamia nut shells) were used as raw materials, and a series of activated carbons (ACs) with high micropore percentage were prepared by hydrothermal carbonization and chemical activation methods, and their dynamic CO2 adsorption capacity was systematically studied. Then the effect of activation conditions and adsorption conditions were all investigated, and the hydrothermal conditions were evaluated in detail. In particular, the relationship between the CO2 uptake and textural properties such as micropore percentage and pore structure was discussed. The results show that the desired AC derived from walnut shells show superior CO2 uptake up to 2.24 mmol g−1 under the dynamic condition, which is comparable with the literature reported. It is also found that the micropore percentage has an important influence on the application of AC for CO2 capture. Both carbonization and activation conditions have significant impact on the CO2 uptake of AC. In addition, to control the CO2 inlet flow rate is essential to obtain a better adsorption effect. This work will give an effective guide to the fabrication of biomass derived AC, particular in preparation of AC based CO2 adsorbents.

Supercritical electrocatalytic catalyst activation and its application in safflower seed oil isomerisation to prepare conjugated linoleic acid

SummaryThe supported Ru/Na‐ZSM‐5 catalyst was prepared by loading Ru on the zeolite support by the impregnation method. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed that Ru was successfully supported. The supported catalyst was subjected to supercritical electrocatalytic activation, and the activated catalyst was applied to the isomerisation of safflower seed oil. The effect of activation conditions on the conjugated linoleic acid (CLA) yield was examined. Under the supercritical CO2 condition, the optimal activation conditions were electrocatalytic current of 200 mA, reaction temperature of 70 °C, stirring speed of 300 r.p.m and reaction time of 1.5 h. The CLA yield was 43.10%, the content of c9,t11‐CLA in the product oil was 17.45% and the content of t10,c12‐CLA was 15.86%, significantly higher than the raw oil. The change was not noticeable in terms of physicochemical properties compared with the raw oil, which met edible vegetable oil quality standards.

Adsorption performance of UiO-66 towards organic dyes: Effect of activation conditions

The Zr-based metal-organic framework (MOF, UiO-66) was synthesized solvothermally. The synthesized UiO-66 was activated using different solvents (acetone, chloroform, and ethanol) via two activation methods of centrifugation and Soxhlet extraction over different periods (1–10 days). The crystalline structure and morphology of the synthesized UiO-66s were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and field-emission scanning electron microscopy (FESEM) techniques. The adsorption behaviors of the synthesized UiO-66s were then investigated by selecting anionic methyl red (MR) and cationic methylene blue (MB) as the model dyes. It was found that a change in activation solvent and activation method would alter the physical properties of UiO-66, such as surface area, pore-volume, pore diameter, and surface charge. Experimental adsorption tests demonstrated that UiO-66 activated by ethanol via the Soxhlet extraction method for five days (abbreviated as ES-5) presented higher MR uptake capacity (243 mg/g) than the other synthesized UiO-66s, ascribed to its large surface area and total pore volume. Furthermore, it was found that the uptake capacity of ES-5 for cationic MB and anionic MR dyes increased and decreased, respectively, with raising the solution pH. This resulted in superior adsorption selectivity of MB over MR at pH 9.1. All in all, the findings of this work showed that the Soxhlet extraction method holds great promise for the activation of different MOFs.

The effects of activation conditions on physical properties of activated carbon

Porous carbons with a high porosity were successfully produced from fast pyrolysis pine wood char via a thermochemical method in which KOH was used as chemical activator. The effects of various weight ratios of KOH to pyrolysis char (0.65:1, 0.7:1, 1.0:1, 1.35:1, and 1.7:1) on the physical properties of activated carbons were investigated. When the weight ratio of KOH to pyrolysis char was 1.35:1, the prepared activated carbon had the highest surface area of 1140 m2/g with a total pore volume of 0.71 cm3/g, a microporous surface area of 957 m2/g, and a microporous specific volume of 0.51 cm3/g. As the weight ratio of KOH to pyrolysis char increased from 0.65 to 1.35, the prepared activated carbon had increases in total surface area, total pore volume, microporous surface area, and specific volume of micropores. However, there was a reverse trend when the weight ratio of KOH to pyrolysis char was higher than 1.35. The use of nitrogen as a flow gas resulted in much more developed activated carbon than without nitrogen. The experiment results suggested that activated carbon with high surface area could be prepared from pyrolysis char by adjusting the activation conditions.

Adsorptive removal of CO2 on Nitrogen-doped porous carbon derived from polyaniline: Effect of chemical activation

Nitrogen-doped porous carbons (NDCs) with high surface areas were prepared using a nitrogen containing polymer (polyaniline) as precursor with H3PO4, ZnCl2 and KOH activation. The effects of activation conditions on the structure of adsorbents and CO2 adsorption were also investigated. The porous structure and surface chemical composition of microporous carbon were analyzed and characterized by N2 adsorption-desorption, elemental analysis (CHNS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effect of temperature on CO2 adsorption was studied at 298, 308 and 318 K on the prepared adsorbents activated by H3PO4, KOH and ZnCl2. Among activating agents studied, H3PO4 was the best activator for the structure development whereas the N-doped porous carbon obtained by ZnCl2 had high CO2 adsorption capacity of 3.54 mmol/g at ambient temperature and pressure with CO2 heat of adsorption energy of 55 kJ/mol at lower surface coverage. The selectivity of CO2 over N2 by H-2,650, Zn-2,500 and K-1,650 (CO2: N2 = 015:0.85, 298 K, 1 bar), predicted by the ideal adsorbed solution theory (IAST) model, were attained 13.65, 26.32 and 6.41, respectively. The multi advantages of these sorbents such as low cost, easy synthesis, lower heat of adsorption, high CO2 uptake capacity and high CO2/N2 selectivity prove the suitability of nitrogen-doped carbons for CO2 capture.

Preparation of Porous Carbon Spheres Under Different Activation Conditions from 2-Keto-l-gulonic Acid Mother Liquor for Electric Double-Layer Capacitor

2-Keto-l-gulonic acid mother liquor (GAML) as an organic waste solution contained highly polluting contents would pollute the environment if discharged directly. As reported in our previous paper, GAML was used as the precursor to prepare porous carbon sphere (PCS) as carbon-based electrode materials of electric double-layer capacitor (EDLC) to create its high value-added utilization, and in the carbonization process, Fe(NO3)3·9H2O acted as an oxidizing agent. Since the carbon sphere was a carbon material with a special morphology, the effect of activation conditions (activation ratio, activation temperature and activation time) on the pore structure and the electrochemical performance of PCS were explored in this paper. PCS was derived via hydrothermal carbonization, carbonization and KOH activation successively, and the as-prepared samples had excellent porosity and high SSA of 2747 m2 g−1. Besides, the specific capacitance of PCS-7-700-1 could reach as high as 303.7 F g−1 (206.5 F cm−3) in 6 M KOH electrolyte at 40 mA g−1.

Effects of activation conditions on the structural and adsorption characteristics of pinecones derived activated carbons

ABSTRACTThis study was conducted to understand and optimize the activation process for the production of a low-cost activated carbon (AC) using a renewable and plentiful biomass waste, pinecones. This was achieved by tracking the changes in porous structure, surface chemistry and adsorption properties of the AC produced using different activating agents, activation temperatures, holding times and heating rates. Generally, produced ACs were predominantly microporous with small external surface area and were different in terms of H/C and O/C ratios. Study of Pb2+ cations adsorption on these samples proved the high affinity of the pinecones derived ACs to this cation. The best adsorption behaviour was recognized in sample prepared by impregnation with H3PO4 at weight ratio of 2, then heating at 400 °C for 2 h at 5 °C/min heating rate. This sample possessed the highest BET surface area (1335 m2/g). The adsorption process obeyed the pseudo-first-order and Freundlich model slightly better than the pseudo-second-order kinetics and Langmuir model. The high Langmuir maximum adsorption capacity of 418 mg/g supports the applicability of the produced AC for the removal of Pb2+ cations from wastewater.

Nitrogen doped hierarchically porous carbon derived from glucosamine hydrochloride for CO2 adsorption

Hydrothermal carbonization (HTC) of biomass is an attractive and sustainable method for the preparation of carbonaceous materials. In this work, nitrogen doped carbon with a hierarchically porous strucutre was successfully prepared through the HTC of glucosamine hydrochloride and the subsequent KOH activation. The resultant carbons were characterized with different techniques, and the effects of activation conditions on the porous structure were also discussed. The carbons showed outstanding CO2 adsorption properties, a high CO2 uptake of 4.5mmol/g was achieved at 298K and 1bar. In order to analyze the influences of nitrogen doping, a pristine carbon sample with very close pore size distribution characteristics but higher porosity was also synthesized with glucose as the carbon precursor. The corresponding CO2 uptake at 298K and 1bar was 3.4mmol/g. Our results revealed that the presence of ultramicropores was an essential prerequisite for CO2 adsorption at ambient conditions, while nitrogen doping showed positive effects on both CO2 uptake and the adsorption selectivity over N2.

Ammonia-Treated Ordered Mesoporous Carbons with Hierarchical Porosity and Nitrogen-Doping for Lithium-Sulfur Batteries

The theoretical specific capacity and energy density of lithium sulfur battery are as high as 1675 mAh/g and 2600 Wh/kg，which is an order of magnitude higher than that of the commercial insertion cathodes. In combination with the natural abundance, low cost and environmental friendliness of sulfur, the Li-S battery becomes a promising candidate for the next generation power source. However，the commercialization of Li-S battery is inhibited by the insulating nature of sulfur and Li2S, the volume expansion, “Shuttle effect” caused by the high solubility of lithium polysulfides in the electrolyte, the severe corrosion of lithium anode and irreversible reaction during the charge/discharge process, which lead to a low utilization rate of sulfur, serious capacity fading, and low Coulombic efficiency of Li-S battery. One of the most effective ways to circumvent these three limitations is to fabricate sulfur/carbon composite cathodes by incorporating sulfur within a variety of carbon materials including porous carbons, carbon nanotubes, graphene nanosheets and many other forms. These carbon hosts can enhance the conductivity of sulfur electrodes and accommodate their volume changes. Furthermore, the weak interactions between carbon and polysulfides also alleviate the dissoluble loss of polysulfide intermediates. In particular, hierarchically porous carbon materials are recently receiving discernable attention. It is believed that the micropores enable better cycle stability due to solvent-restricted lithiation/delithiation of sulfur, while the larger pores (mesopores and macropores) promise high sulfur loading and rapid ion transport. Therefore, both of large capacity and high rate performance may be achieved. Further, the nitrogen doping of carbon materials has been recently demonstrated to be a powerful method for enhancing the overall electrochemical performance of sulfur cathodes. The nitrogen heteroatom with high electronegative improves the carbon conductivity and promotes chemical adsorption of polysulfides, resulting in enhanced sulfur utilization, rate capability, and cyclic stability. For these reasons, it is essential to develop facile and scalable methods to prepare nitrogen-doped carbon materials with hierarchical porosity. However, there is a trade-off between well-developed porosity and high nitrogen-doping level. Generally, current methods that favor high nitrogen contents tend to result in low specific surface area or small pore volume, or vice versa. To produce hierarchical porous carbon materials with both developed porosity and high nitrogen content, we herein introduce a simple and cost-efficient approach using two ease-to-scale-up steps including 1) one-pot aqueous self-assembly route to firstly get nitrogen-doped ordered mesoporous carbons (NOMCs) and then 2) ammonia activation treatment to achieve desirable porosity and nitrogen-doping. For comparison, another important and industrial method, KOH activation, was also used to obtain hierarchically porous carbon. Those gained carbons were then used as the sulfur hosts in the Li-S batteries. The effect of activation conditions on the nitrogen content, specific surface area, and pore size distribution of the hierarchically porous carbons as well as their electrochemical performance were investigated in detail. It clearly exhibits that ammonia activation enables the hierarchically porous carbon with relatively high porosity (specific surface area up to 1565 m2 g−1) and nitrogen content (up to 4.4 wt%). These combined superior properties make them good candidates as the host materials of sulfur cathodes in Li-S batteries with high sulfur loading.

Chemically activated carbon from lignocellulosic wastes for heavy metal wastewater remediation: Effect of activation conditions

Chemical activation is known to induce specific surface features of porosity and functionality which play a definite role in enhancing the adsorptive potential of the developed activated carbons. Different conditions of temperature, time, reagent type and impregnation ratio were applied on sawdust precursor and their effect on the physical, surface chemical features and finally on the adsorption potential of the developed activated carbons were analysed. Under activation conditions of 600°C, 1hr, 1:0.5 ratio, ZnCl2 impregnated carbon (CASD_ZnCl2) resulted in microporosity while KOH impregnation (CASD_KOH) yielded a carbon having a wider pore size distribution. The surface chemistry revealed similar functionalities. At same pH, temperature and adsorbate concentrations, CASD_KOH demonstrated better adsorption potential (1.06mmoles/g for Cd2+ and 1.61mmoles/g for Ni2+) in comparison to CASD_ZnCl2 (0.23mmoles/g and 0.33mmoles/g for Cd2+ and Ni2+ respectively). Other features were a short equilibrium time of 60mins and an adsorbent dose of 0.2g/L for the CASD_KOH in comparison to CASD_ZnCl2 (equilibrium time of 150min and dosage of 0.5g/L). The nature of interactions was physical for both adsorbents and pore diffusion mechanisms were operative. The results reveal the potentiality of chemical activation so as to achieve the best physico-chemical properties suited for energy efficient, economical and eco-friendly water treatment.

CO2 Capture in the Sustainable Wheat-Derived Activated Microporous Carbon Compartments.

Microporous carbon compartments (MCCs) were developed via controlled carbonization of wheat flour producing large cavities that allow CO2 gas molecules to access micropores and adsorb effectively. KOH activation of MCCs was conducted at 700 °C with varying mass ratios of KOH/C ranging from 1 to 5, and the effects of activation conditions on the prepared carbon materials in terms of the characteristics and behavior of CO2 adsorption were investigated. Textural properties, such as specific surface area and total pore volume, linearly increased with the KOH/C ratio, attributed to the development of pores and enlargement of pores within carbon. The highest CO2 adsorption capacities of 5.70 mol kg−1 at 0 °C and 3.48 mol kg−1 at 25 °C were obtained for MCC activated with a KOH/C ratio of 3 (MCC-K3). In addition, CO2 adsorption uptake was significantly dependent on the volume of narrow micropores with a pore size of less than 0.8 nm rather than the volume of larger pores or surface area. MCC-K3 also exhibited excellent cyclic stability, facile regeneration, and rapid adsorption kinetics. As compared to the pseudo-first-order model, the pseudo-second-order kinetic model described the experimental adsorption data methodically.

Rapeseed and Raspberry Seed Cakes as Inexpensive Raw Materials in the Production of Activated Carbon by Physical Activation: Effect of Activation Conditions on Textural and Phenol Adsorption Characteristics.

The production of activated carbons (ACs) from rapeseed cake and raspberry seed cake using slow pyrolysis followed by physical activation of the obtained solid residues is the topic of this study. The effect of activation temperature (850, 900 and 950 °C), activation time (30, 60, 90 and 120 min) and agent (steam and CO2) on the textural characteristics of the ACs is investigated by N2 adsorption. In general, higher activation temperatures and longer activation times increase the BET specific surface area and the porosity of the ACs, regardless of the activation agent or raw material. Steam is more reactive than CO2 in terms of pore development, especially in the case of raspberry seed cake. The performance of the ACs in liquid adsorption is evaluated by batch phenol adsorption tests. Experimental data are best fitted by the Freundlich isotherm model. Based on total yield, textural characteristics and phenol adsorption, steam activation at 900 °C for 90 min and CO2 activation at 900 °C for 120 min are found as the best activation conditions. Raspberry seed cake turns out to be a better raw material than rapeseed cake. Moreover, AC from raspberry seed cake produced by steam activation at 900 °C for 90 min performs as well as commercial AC (Norit GAC 1240) in phenol adsorption. The adsorption kinetics of the selected ACs are best fitted by the pseudo-second-order model.