Valorization of Casuarina empty fruit-based activated carbons for dyes removal - Activators, isotherm, kinetics and thermodynamics

The present work was aimed to evaluate the adsorption properties of Casuarina fruit-based activated carbons to remove cationic (methylene blue) and anionic (congo red) dyes. The roles of activators on the characteristics and performance of activated carbons were studied. Activated carbons were characterized for textural characteristic, surface morphology, surface functional groups, elemental composition, thermal degradation analysis and pH at the zero point of charge (pHpzc). The specific surface of the materials is between 2.33 m(2)/g and 1511 m(2)/g. Batch adsorption was conducted at varying concentrations, contact times and temperatures. Results show that KOH activation yields activated carbon with excellent maximum capacities of 615 mg/g and 339 mg/g for methylene blue and congo red, respectively. The adsorption data displayed a good regression with Langmuir and pseudo-second-order kinetic models. Both intraparticle and film controlled the diffusion of dye molecules onto the carbon surface. The adsorption is endothermic and spontaneous at high temperature especially for methylene blue removal.