Removal of Direct Red 12B from aqueous medium by ZnCl2 activated Jatropha husk carbon: Adsorption dynamics and equilibrium studies

Abstract

Adsorption isotherms and kinetics of adsorption of Direct Red 12B (DR 12B) on zinc chloride activated carbon prepared from Jatropha husk (ZAJHC) have been determined from batch tests. Effects of contact time, initial dye concentration, initial pH, adsorbent dose and solution temperature have been investigated. The equilibrium data are best represented by Langmuir isotherm model, showing monolayer adsorption capacity (Q_o) of 39 mg g^-1. The kinetic data are fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and are found to follow closely the pseudo-first-order kinetic model. Thermodynamic parameters such as standard enthalpy (∆H^o), standard entropy (∆S^o) and standard free energy (∆G^o) have been evaluated. The adsorption interaction is found to be endothermic in nature. Acidic pH is favourable for the adsorption of DR 12B. Desorption studies show that chemisorption seems to be the major mode of adsorption. ZAJHC is shown to be a promising adsorbent for removal of DR 12B from aqueous solutions.