Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Toluidine Blue also known as Tolonium Chloride is an acidophilic metachromatic dye which selectively stains acidic tissue components (sulfates, carboxylates, and phosphate radicals).It is a member of the thiazine group and is partially soluble in both water and alcohol. Toluidine blue has been known for various medical applications. In this study, adsorption of Toluidine Blue, on SiO2 nanoparticles was investigated using a batch adsorption technique. In order to reach a maximum removal efficiency (R%), optimum conditions were explored by means of experimental design approach. The experimental factors were considered such as: pH, contact time, sorbent dosage and dye concentration in the solution. Response surface methodology (RSM) including faced central composite design (FCCD) was employed to optimize the removal conditions and to propose an appropriate regression models along with related surface plots. Second-order kinetic model described well the dynamic behavior of the current adsorption process. The desorption efficiencies with HCl, HNO3, CH3COOH and NaOH were low. Also it was found that presence of Na+, K+,Ca2+ and Mg2+ ion have no significant interference on adsorption efficiency. FT-IR analysis identified that the functional groups of sorbent were involved in the adsorption process.
