Adsorption of phosphate from wastewater by a ZnO-ZnAl hydrotalcite

A ZnO-ZnAl hydrotalcite (ZZA) was prepared by a new centrifugal method, and its micromorphology was characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses. The adsorption by ZZA of phosphate in a simulated wastewater was studied in detail. The effects of a variety of factors, including pH, coexisting ions, adsorption time, ZZA dosage, and adsorption temperature, on the phosphate adsorption were evaluated. The reaction of ZZA adsorbing phosphate in the simulated wastewater may be an endothermic reaction. The adsorption process is more in line with the Langmuir model equation, indicating that it may be homogeneous surface monolayer chemisorption. By studying the thermodynamic index of ZZA adsorbing phosphate in simulated wastewater, it was suggested that the adsorption is a spontaneous, endothermic, and entropy-increasing process. For moderate and low level of phosphate amount wastewater, the emission requirements can be met.