Adsorption of Rhodamine B dye from aqueous solution onto acid activated mango (Magnifera indica) leaf powder: Equilibrium, kinetic and thermodynamic studies

Abstract

Acid activated mango leaf powder (MLP) was employed for removal of the rhodamine B (RB) dye from aqueous solution. Batch adsorption studies were carried out under varying conditions of dye concentration, adsorbent dose, particle size, contact time, pH, and temperature. Removal efficiency was 77% in 45 min with 6.0 pH, 25 g/L as dose, 250 mg/L RB concentration and 30°C temperature. The equilibrium data the best fitted with Langmuir model. The adsorption followed Lagergren pseudo-first order kinetics. The values of free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) indicated the process to be spontaneous. The diffusion studies indicated that adsorption initially takes place by external mass transfer and later by intraparticle diffusion. The results indicate that MLP is a good adsorbent for the removal of RB from wastewater.   Key words: Acid activated mango leaf powder, adsorption, Rhodamine B, isotherms, kinetics, thermodynamics.