Al30 polycation pillared montmorillonite preparation and phosphate adsorption removal from water

Abstract

Phosphorus removal from surface water is a key to control eutrophication issues. Among phosphorus removal strategies, clay adsorption materials have been studied widely due to various advantages. Yet, raw montmorillonite (MMT) has limited adsorption capacity for phosphate. In order to improve the adsorption performance of MMT for phosphate, aluminum polycation Al30 was used as a pillaring agent to modify MMT material, and response surface method was used to optimize the preparation process. The optimal conditions were obtained as: [OH−]/[Al3+] molar ratio of 2.4:1, Al/MMT ratio of 4:1, curing time of 12 h, reaction temperature of 77.5 °C, and alkali adding rate of 1.55 mL/min. After modification, the properties of MMT were improved obviously and the adsorption of phosphate in solution was enhanced. Investigation results indicate that the acid environment is more favorable for the adsorption of phosphate by Al30-MMT. The adsorption of phosphate by Al30-MMT accords with Langmuir model with maximum adsorption of 62.5 mg/g at 318 K and pseudo-second order kinetic model. The main adsorption mechanisms of Al30-MMT in the process of phosphate removal include electrostatic physical adsorption and anion exchange.