Equilibrium uptake and sorption dynamics for the removal of reactive dyes from aqueous solution using activated carbon prepared from Euphorbia tirucalli L wood

Activated carbon prepared from Euphorbia tirucalli L wood (ETAC) by chemical activation with phosphoric acid has been analysed for the removal of Reactive Red and Reactive Blue dyes from aqueous solutions through batch adsorption technique. Lower solution pH favours the adsorption of reactive dyes. The amount of dye adsorbed per unit mass of adsorbent increases with the increase in temperature and initial dye concentration. Freundlich and Langmuir models are used to analyze the equilibrium data at different temperatures. The equilibrium data for the adsorption of both dyes are better described by the Langmuir isotherm model. The adsorption of reactive dyes follows second order kinetics along with intra-particle diffusion model. Thermodynamic parameters such as free energy change, enthalpy change and entropy change for adsorption of reactive dyes show that the adsorption of Reactive Red and Reactive Blue onto ETAC are spontaneous, endothermic and physical adsorption. Activation energy and isosteric heat of adsorption suggests that adsorption of reactive dyes onto ETAC is a physical process.