Adsorption of Methylene blue from aqueous solutions by modified nano-TiO2

Methylene blue (MB) is the cationic dye that is most commonly used for coloring. It is generally used for dyeing cotton, wool, and silk [1,2]. MB can cause eye burns in humans and animals, cyanosis, convulsions, tachycardia, dyspnea, irritation to the skin, and if ingested, irritation to the gastrointestinal tract, nausea, vomiting, and diarrhea [3]. Thus, development of suitable methods for the decontamination of MB is necessary. In this research, adsorption capacity of MB onto modified TiO2 nanoparticles was investigated in a batch system by considering the effects of various parameters like contact time, adsorbent dosage, pH, initial dye concentration and temperature. Optimum conditions for MB adsorption were found to be pH≈7, 0.4 g of adsorbent and equilibrium time≈50 min. The results showed that the increase of temperature and initial MB concentration leads to gradual decreas of adsorption rate. Evaluation of non-linear adsorption isotherm and kinetic models by Polymath software suggested that data can be well described by the pseudo-second-order kinetic and Freundlich isotherm models. Thermodynamic studies showed that the adsorption process was spontaneous and exothermic.