Optimization and characterization of paddy stalks-based activated carbon by physical activation: Box-Behnken design approach

Improper disposal of paddy stalks residue via open burning or soil incorporation creates contamination hazards by releasing particulate matter, residue ash, and breakdown chemicals into the environment. This study aimed to repurpose these stalks by converting them into activated carbon. Box Behnken Design BBD within the response surface methodology (RSM) framework was adopted. The independent variables of the preparation conditions were the holding time, heating rate and activation temperature. The optimization process response was the surface area of activated carbon. The paddy stalks based activated carbon (PSAC) was subjected to a suite of physicochemical characterization techniques including BET, FTIR, XRD and SEM. The highest surface area of 488.6 m²/g was obtained at heating rate of 10 min/°C, contact time of 120 min and activation temperature of 500 °C. The statistical analysis showed that contact time achieved the highest significancy, followed by activation temperature and heating rate. The activated carbon exhibited pore sizes spanning from 2 nm to over 269 nm, creating pores sufficiently broad to fit some toxic contaminants. The findings demonstrate the viability of paddy stalks for activated carbon production, introducing a sustainable stalk residue disposal solution that promotes environmental sustainability.