Abstract: Eutrophication caused by excess phosphate in water bodies is an important issue in China and many countries (regions) around the world. Therefore, it is crucial to investigate the environmental geochemical behavior of phosphate and to explore phosphorus removal techniques and principles. In this study, a Ce-Al oxide was synthesized as the adsorbent material to investigate the adsorption behavior and mechanism of orthophosphate. The effects of system parameters such as reaction time, initial phosphate concentration, pH and ionic strength on the phosphate adsorption by the Ce-Al oxide were examined. The results showed that the phosphate adsorption reached equilibrium within 24 hours; the adsorption isotherm (pH=7) was best fitted by Langmuir adsorption mode, yielding a maximum adsorption amount of 75.5 mg·g-1; and importantly the adsorption was insensitive to pH and maintained a high efficiency in the studied pH range (i.e. pH=3-10). This study further employed zeta potential measurement, microscopic analyses (SEM and TEM) and spectroscopic methods (XRD and XPS) to investigate the phosphate adsorption mechanisms by the Ce-Al oxide. It can be concluded that surface precipitation and inner-sphere adsorption dominates the phosphate adsorption mechanisms by the Ce-Al oxide. The study demonstrates that the Ce-Al oxide is a candidate material for phosphate removal.

Key words: Ce-Al oxide, phosphate, adsorption, adsorption mechanism, XPS