Kinetics and equilibrium adsorption of Basic Green 4 dye on activated carbon derived from durian peel: Effects of pyrolysis and post-treatment conditions

Durian peel was evaluated as raw material for the production of activated carbon used in adsorption of dyes. The synthesis of activated carbon was based on either nitrogen atmospheric or vacuum pyrolysis, followed by CO2 activation. Post-treatment of synthesized activated carbon with acid or base solution was performed. Activated carbon synthesized under vacuum pyrolysis had better properties (BET surface area, pore volume and adsorption capacities) than that under nitrogen atmospheric pyrolysis. Improvement in such properties was also observed when activated carbon was post-treated with HCl solution. Rather than surface modification, removal of impurities was responsible for this improvement. The HCl-treated activated carbon best adsorbed Basic Green 4 dye compared to acid dyes. Adsorption of Basic Green 4 dye was well explained with pseudo-second-order kinetics. The experimental adsorption equilibrium data were fitted to Langmuir and Freundlich models, with the former providing the best fit. The maximum adsorption capacities of activated carbons synthesized under nitrogen atmospheric and vacuum pyrolysis were very high (303.0 and 312.5 mg/g, respectively).