Effects of pH and ionic strength on methylene blue removal from synthetic aqueous solutions by sorption onto orange peel and desorption study

The aim of this work is to study the efficiency of waste material ‘’orange peel’’ for the removal of methylene blue from synthetic aqueous solutions in batch conditions. The effects of initial pH and ionic strength of solution on the dye sorption kinetics has been studied at ambient temperature (25°C). A desorption tests on material, previously saturated with dye, were undertaken in distilled water at different pH values. The results showed that the sorption kinetics of the quantity of dye uptake at equilibrium depends with initial pH and the ionic strength in solution. For each parameter study, the kinetic model of pseudo-second order proved to be adequate to describe the results of sorption dye kinetics and the model of Langmuir has been found perfectly adequate to describe the equilibrium results of sorption. The maximal capacities (Qmax) of methylene blue sorption decrease from 280 to 98 mg/g when the initial pH of solution decreases from 9 to 3 and from 205 to 74 mg/g when the NaCl concentration in solutions increases from 0.00 to 0.10 mol/L.