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Author: search.filters.author.Eiad-ua, ApiluckSubject: search.filters.subject.Chemical activation

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    Chemically activated carbons derived from cashew nut shells as potential electrode materials for electrochemical supercapacitors
    (2025-06-01)
    Chaiammart, Nattapat
    ;
    Vignesh, Veeramuthu
    ;
    Thu, Myo Myo
    ;
    Eiad-ua, Apiluck
    ;
    Maiyalagan, Thandavarayan
    Supercapacitors are widely recognized as energy storage solutions due to their high power densities and long cycle lives. Furthermore, there is growing scientific and technological interest in converting biomass waste into carbon materials for manufacturing supercapacitor electrodes. In addition to their abundance and cost-effectiveness, the appeal of carbons derived from biomass lies in their tunable porosity, which enables the rational design of carbon materials to achieve the desired performance of supercapacitors. Here, we present the synthesis of activated carbons from cashew nut shells via potassium hydroxide (KOH) activation at different temperatures (650, 750, and 850 °C). The resulting materials exhibited amorphous and predominant microporous structures. Increasing the activation temperature led to a rise in specific surface area from 1534 to 2034 m<sup>2</sup> g<sup>−1</sup> and an increased proportion of mesopores. The electrochemical properties of these activated carbons for supercapacitor applications were investigated by cyclic voltammetry, galvanostatic charge–discharge, and impedance spectroscopic techniques in a 1 M sodium sulfate (Na<inf>2</inf>SO<inf>4</inf>) electrolyte. Using a three-electrode system, the activated carbons treated at 750 °C exhibited a maximum specific capacitance of 106 F g<sup>−1</sup> at a current density of 0.5 A g<sup>−1</sup> with a good rate capability; they retained 75 % at 10 A g<sup>−1</sup> over a 1.0 V voltage window. Furthermore, a symmetric supercapacitor coin-cell, fabricated with activated carbons treated at 750 °C as the positive and negative electrodes, demonstrated an energy density of 2.43 Wh kg<sup>−1</sup> at a power density of 1002 W kg<sup>−1</sup>. The cell exhibited 87 % capacitance retention at 1.0 A g<sup>−1</sup> after 10,000 cycles. This work showcases the efficient and sustainable utilization of cashew nut shells as a carbon source for supercapacitor applications and highlights their value in a circular economy.
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    Synthesis of nanoporous carbon from brewer waste by hydrothermal carbonization assisted chemical activation for carbamazepine adsorption
    (2024-06-01)
    Apinyakul, Naruemon
    ;
    Chanpee, Sirayu
    ;
    Kaewtrakulchai, Napat
    ;
    Khemasiri, Narathon
    ;
    Eiad-ua, Apiluck
    Nanoporous carbon (NPC) has gained significant attention in wastewater treatment due to its effectiveness. The adsorption process, known for its simplicity, stability, and cost-effectiveness, is widely recognized as an efficient method for removing carbamazepine (CBZ) residues accumulate in the environment. However, the application of NPC is often hindered by challenges in the regeneration process after use, as well as issues related to large surface area, pore size, and functional groups. Fortunately, the samples in this study not only maintained their adsorption efficiency but also demonstrated the ability to be regenerated multiple times. Herein brewery waste was subjected to hydrothermal treatment at 200 °C for 1 h and followed by KOH and NaCl activation with different KOH:NaCl (w/w) ratios of 5:0, 4:1, 3:2, 1:1, 2:3, 1:4, and 0:5 to optimize the properties of malt husk derived nanoporous carbon (NPC). The optimal condition KOH:NaCl ratio of 1:1 had a maximum specific surface area of 906 m<sup>2</sup>/g with a total pore volume of 0.252 cm<sup>3</sup>/g. According to the adsorption test, the CBZ adsorption isotherm was well-fitted to the Langmuir model (R<sup>2</sup> = 0.976) kinetic data were consistent with the pseudo-second-order model (R<sup>2</sup> = 0.995). This suggests that the adsorption mechanism involves monolayer adsorption and chemisorption interaction. The Gibbs free energy and enthalpy of CBZ adsorption by NPC were found to be spontaneous and endothermic. The regeneration test revealed a 95.35% decrease in the adsorption capacity of NPC after 5 repeated cycles. Consequently, the study suggests a potential application of nanoporous carbon from MH as an alternative adsorbent for removing carbamazepine in wastewater.