Study of phosphate removal from aqueous solution by zinc oxide

J Water Health. 2015 Sep;13(3):704-13. doi: 10.2166/wh.2015.210.

Abstract

Zinc oxide (ZnO) was synthesized and used to investigate the mechanism of phosphate removal from aqueous solution. ZnO particles were characterized by X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy before and after adsorption. Batch experiments were carried out to investigate the kinetics, isotherms, effects of initial pH and co-existing anions. The adsorption process was rapid and equilibrium was almost reached within 150 min. The adsorption kinetics were described well by a pseudo-second-order equation, and the maximum phosphate adsorption capacity was 163.4 mg/g at 298 K and pH ∼6.2±0.1. Thermodynamic analysis indicated the phosphate adsorption onto ZnO was endothermic and spontaneous. The point of zero charge of ZnO was around 8.4 according to the pH-drift method. Phosphate adsorption capacity reduced with the increasing initial solution pH values. The ligand exchange and Lewis acid-base interaction dominated the adsorption process in the lower and the higher pH range, respectively. Nitrate, sulfate and chloride ions had a negligible effect on phosphate removal, while carbonate displayed significant inhibition behavior.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Hydrogen-Ion Concentration
  • Phosphates / chemistry
  • Phosphates / isolation & purification*
  • Thermodynamics
  • Water Pollutants, Chemical / chemistry
  • Water Pollutants, Chemical / isolation & purification*
  • Water Purification
  • Zinc Oxide / chemistry*

Substances

  • Phosphates
  • Water Pollutants, Chemical
  • Zinc Oxide