Synthesis of activated carbon via microwave heating for dyes removal
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Date
2018-09-01
Authors
Siti Ruqayyah Ab Hamid
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Abstract
Methylene blue, (MB) as basic dye and metanil yellow (MY) as acid dye dissolved in water to produce negative and positive ions respectively. These ions were electrostatically attracted to the polar side of water molecules, thus making MB and MY difficult to be removed. Therefore, an effort was made to produce activated carbon (AC) from durian seed and jackfruit seed for MB and MY dyes removal from aqueous solution. These ACs were produced by employing microwave irradiation technique as heat treatment and physicochemical activation via potassium hydroxide (KOH) chemical treatment and carbon dioxide (CO2) gasification treatment. The preparation conditions of these ACs (radiation power, radiation time and impregnation ratio, (IR)) were optimized with the help of response surface methodology (RSM) in order to produce maximum value of responses (MB removal, MY removal, and AC’s yield). Durian seed based AC (DSAC) and jackfruit based AC (JSAC) prepared were found to pose relatively high Bruneaur-Emmet-Teller (BET) surface area and fixed carbon percentage which were (852.30m2/g and 78.51%) and (715.29m2/g and 73.94%) respectively. Optimum preparation conditions were determined to be (330W, 4.49min and 0.97 with 79.67% of MB removal and 23.60% of yield), (355W, 4.15min and 0.58 with 77.68% of MB removal and 24.40% of yield), (340W, 4.44min and 0.94 with 78.24% of MY removal and 23.51% of yield ) and (370W, 4.10min and 0.78 with 77.24% of MY removal and 23.67% of yield) for MB-DSAC, MB-JSAC, MY-DSAC and MY-JSAC systems respectively. Isotherm studies revealed that all adsorbate-adsorbent systems were best described by Freundlich model whereas kinetic studies revealed that all systems followed pseudo-second order kinetic model. Mechanism studies conducted found that the rate limiting step in adsorption process of all systems were contributed by film diffusion. Thermodynamic studies confirmed that all adsorption systems were exothermic in nature, spontaneous and governed by physisorption.