Mesoporous carbon-based material from Nephelium mutabile via thermochemical pyrolysis process: Characterizations and optimization for crystal violet dye removal

Abstract

In this study, pulasan (Nephelium mutabile) fruit peel (PUP) waste was transformed into activated carbon (PUP-AC) martial via thermochemical pyrolysis process using microwave-assisted ZnCl₂ activation. The physicochemical properties of PUP-AC were investigated using several analytical techniques including BET, XRD, pH_pzc, FTIR, and SEM-EDX. Afterward, the ability of PUP-AC to adsorb toxic organic dye namely crystal violet (CV) from aqueous environment was investigated. Thus, Box-Benken design (BBD) and the desirability function approach were applied to identify the optimal adsorption conditions for CV removal including contact time (20–180 min), pH of the solution (4–10), and PUP-AC dosage (0.02–0.1 g/100 mL). The Langmuir isotherm model is the best model that describes the adsorption isotherm data for CV dye with a maximum adsorption capacity of 225.1 mg/g at optimal desirability function conditions (PUP-AC dosage 0.097 g/100 mL and solution pH = 8.2). The mechanism of CV adsorption by the PUP-AC can be attributed to the pores filling, hydrogen bonding, electrostatic attraction, and π-π stacking. The output of this study presents PUP as a potential precursor for producing porous activated carbon with desirable property for removing cationic dyes from an aqueous environment.