Phosphate adsorption and desorption on two-stage synthesized amorphous-ZrO2/Mg–Fe layered double hydroxide composite

Abstract

Although different treatment techniques have been developed to eliminate phosphorus contamination, including for wastewater treatment, treated water often fails to meet quality regulations. Amorphous-ZrO2/Mg–Fe layered double hydroxide (LDH) composites with different molar ratios (Zr/Fe = 0.5–2) were prepared in two-stage synthesis by the combination of coprecipitation and hydrothermal methods. The requirement of high-temperature calcination in the LDH for phosphate adsorption could be eliminated by the synthesis of the composite. Moreover, the phosphate adsorption ability of the composite was higher than that of the individual LDH and amorphous-ZrO2. The addition of ZrO2 increased the phosphate adsorption ability of composite at low pH. The adsorption capacity was increased by decreasing the pH and increasing the temperature (from 290 to 324 K). The bicarbonate (HCO3−) was the most competitive anion for phosphate adsorption. The pseudo-second-order model provided the best description of the kinetic adsorption data. Furthermore, the adsorbed phosphate was easily desorbed by 1 N of NaOH solution. The results suggest that the amorphous-ZrO2/Mg–Fe LDH composite is a promising material for phosphate removal and recovery from wastewater. Ongoing research will investigate the performance of the composite for real wastewater as well as the mechanism of phosphate adsorption on the composite surface.