Effect of Calcination and Ca-modified on Bentonite and Zeolite, with Respect to Phosphorus Removal from Aqueous Solution

Abstract

The effect of the thermal treatment and Ca-modification on bentonite (Bent) and zeolite (Z) was investigated for the ability of phosphorus sorption. Bentonite and zeolite were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer Emmett Teller (BET) specific surface area, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX). The XRD analysis indicated that montmorillonite and clinoptolite were the main minerals in bentonite and zeolite, respectively. Bentonite and zeolite were exposed to calcination and hydrothermal treatments with CaCl2 (0.1M) at different temperatures (200, 400, 600, 800, and 1000 o C) for 2 hr. The final reaction products were inspected, by XRD, FTIR, SEM, and EDX.The result of the thermal treatments was a significant loss of crystallinity and their structure in calcination than in hydrothermal treatments as a possible consequence of the increase of calcium ions and changing the Si/Al ratio. Further, batch equilibrium experiments were carried out at room temperature (25 o C) for 24 hr to investigate the effect of thermal treatment of Bent and Z for their ability for phosphorus sorption. The removal ability of phosphorus decreased with the increasing temperature of the thermal treatment of the sorbents as a result of the decreases in pore volume, and surface area. Bent and Z hydrothermal treatments less than 1000 o C indicated the enhancement effect of the calcium bending minerals on phosphorus removal ability.