Effect of Microwave-Assisted CO2 Pyrolysis on the Production of Activated Carbon from Confiscated Cigarettes

Abstract

Confiscated cigarettes are a significant problem worldwide, and in Malaysia, the Royal Malaysian Customs Department (RMCD) Perlis had confiscated 1.5 billion sticks of cigarettes from 2016 to 2019 and the cost of disposal reached RM1.2 billion. Confiscated cigarettes are commonly disposed by incineration which can cause environmental pollution. In this study, the cigarette tobacco was converted into activated carbon (AC) via microwave-assisted CO₂ pyrolysis. The tobacco was first carbonized at 300℃, followed by carbon dioxide (CO₂) activation under microwave heating. The highest yield, 31% was obtained at 616W for 6 min. The BET surface area for tobacco, char and the best AC produced were 1.99, 1.21 and 1.69 m²/g, respectively. Response surface methodology (RSM) of dye removal from AC showed that the optimum condition with the best adsorption properties was achieved at 364 Watt for 2 minutes, which resulted in 87.4% removal of methylene blue (MB). Due to the low surface area, the capability of the AC to adsorb MB dye might be assisted by a diversified factors that contributes to the adsorption mechanism. Modelling of the adsorption data also showed that the adsorption process occurs in multilayers of the adsorbent, best fit to the Freundlich isotherm. Microwave-assisted CO₂ pyrolysis shows potential in the production of AC from tobacco and could be further improved to increase the surface area.