Synthesis, characterization and application of mesoporous silica in removal of cobalt ions from contaminated water

Mesoporous silica was synthesized by a chemical precipitation process and its efficiency was investigated for removal of cobalt ions (Co2+) from the contaminated water in a laboratory scale. The characteristic of the synthesized mesoporous were analyzed by SEM image. Optimal conditions were determined for important parameters such as solution pH, the absorbent dose, the initial Co2+ concentration and contact time by a one-variable method through the batch experiments. The SEM results confirmed the synthesized silica had high porosity with a honeycomb-like structure. The results showed that increase the adsorbent dose and contact time to the optimum increased the efficiency of Co2+ adsorption. However, with increasing the concentration of Co2+, the removal efficiency was decreased. The removal of Co2+ was 85% at the optimal contact time of 8 h. The maximum adsorption efficiency was 89% at pH = 7, initial Co2+ concentration of 5 ppm, and the adsorbent dose of 0.3 g/50 ml. The study of adsorption isotherm and kinetic models indicated that the adsorption process followed the Freundlich isotherm (R-2 = 0.9359) and the second-order kinetic model (R-2 = 0.9995). The synthesized mesoporous silica presented a chemical adsorption mechanism for Co2+ removal from aqueous media and it can be used in wastewater treatment containing bivalent heavy metals such as Co2+.