Application of central composite design for simultaneous removal of methylene blue and Pb(2+) ions by walnut wood activated carbon.

Activated carbon was prepared from walnut wood which was locally available, non-toxic, abundant and cheap. This new adsorbent was characterized using BET, FTIR and SEM. Point of zero charge (pHpzc) and oxygen containing functional groups were also determined. The prepared adsorbent was applied for simultaneous removal of Pb(2+) ions and methylene blue (MB) dye from aqueous solution. The prominent effect and interaction of variables such as amount of adsorbent, contact time, concentration of MB and Pb(2+) ions were optimized by central composite design. The equilibrium data obtained at optimum condition were fitted to conventional isotherm models and found that Langmuir model was the best fitted isotherm. Kinetic data were fitted using various models. It was revealed that the adsorption rate follows pseudo-second order kinetic model and intraparticle diffusion model.