Effect of Phosphate on Ultrafiltration Membrane Performance After Predeposition of Fe3O4

The effect of predeposition of Fe3O4 on ultrafiltration (UF) processes has been widely studied in recent years. However, there have been no reports of effects of phosphate on the predeposition process. In this article, the fluxes of humic acid (HA) solutions filtered by Fe3O4+UF and Fe3O4+H2PO4-+UF were studied and filtered water was analyzed. Results indicate that the optimum concentration of Fe3O4 for the predeposition process was 0.45g/L. Filtration fluxes of HA solutions using UF, Fe3O4+UF, and Fe3O4+H2PO4-+UF were 0.32, 0.52, and 0.41, respectively, after 10min. Removal efficiencies of HA filtrated by UF, Fe3O4+UF, and Fe3O4+H2PO4-+UF were 32.6%, 41.1%, and 35.8%, respectively, according to dissolved organic matter results. After Fe3O4 adsorbed phosphate, the effect of Fe3O4 predeposition on removal of high and medium molecular weight HA was weaker. However, Fe3O4 predeposition enhanced removal of low molecular weight HA. Scanning electron microscopy and atomic force microscopy demonstrated that phosphate decreased compactness of the Fe3O4 predeposition layer. These data provide new insights into use of Fe3O4 predeposition in UF applications.