Adsorptive removal of phosphate ions from aqueous solution using zirconia-functionalized graphite oxide

Abstract

A new zirconia-functionalized graphite oxide was synthesized and its adsorption performance for the removal of phosphate in water was evaluated by batch and column tests. The adsorbent was characterized by X-ray powder diffraction, transmission electron microscope, Fourier transform infrared spectra, N2 adsorption–desorption, X-ray photoelectron spectroscopy, X-ray fluorescence and zeta potential measurements. Results showed that adsorption kinetics followed the pseudo-second-order model and the adsorption isotherm could be well described by the Langmuir adsorption model. Markedly enhanced phosphate adsorption was observed on zirconia-functionalized graphite oxide compared with graphite oxide due to the strong phosphate adsorption on ZrO2 and effective dispersion of nanosized ZrO2 on graphite oxide surface. Phosphate adsorption was suppressed by increasing pH, while slightly influenced by solution ionic strength. Column tests were conducted at a fixed flow rate at room temperature and both Thomas and Yoon–Nelson models were found to be suitable for describing the dynamic behavior. The adsorbent exhibited stable adsorption–desorption behavior in 11 consecutive test cycles. The present study highlights the potential of using zirconia-functionalized graphite oxide as effective and regenerable adsorbent for the removal of phosphate in water.