Sulfate removal from acid mine drainage using Al, Fe-pillared nano bentonite

High concentration of sulfate in acid mine drainage is one of a chemical pollutants which can cause various health problems and damage the wastewater piping systems if not enough attention is given to its removal. In this research, adsorption process was selected as an effective, simple and low-cost method for sulfate removal. The modification of clay minerals as a natural and eco-friendly adsorbent is very useful for improving their properties along with permanent porosity. In recent years, pillared clay has been received much attention. In this study, the structural properties of Al, Fe-pillared nano bentonite is improved by using the combined ultrasonic wave and microwave irradiation technology. In this adsorbent, the synthetic duration time and water consumtion are reduced and the number of active sites are increased. Therefore, an effective adsorbent is produced with high absorption capacity compared to the initial bentonite sample. In this study, the thermodynamic parameters was calculated by examining the effect of temperature, while the adsorption data are fitted by Freundlich, Langmuir and Temkin isotherm models. The thermodynamic results showed that the adsorption process for both initial and pillared bentonite were exothermic and spontaneous. Second-order kinetic models and intra-particle diffusion model demonstrated that the main adsorption mechanism was chemical absorption with penetration into the absorbent porous media, especially in the pillared sample.