The use of iron oxide-coated ceramic membranes in removing natural organic matter and phenol from waters

Ceramic tight-ultrafiltration (UF) membranes were coated with iron oxide layers to investigate the removals of phenol and/or natural organic matter (NOM) from waters. The effects of iron oxide coating on NOM rejections were dependent on NOM characteristics in waters. Iron oxide coating of the membrane increased NOM rejections in a water with high specific UV absorbance (SUVA) value, due to sorption of NOM, especially the UV280 absorbing fractions, to the iron oxide surfaces. In the low-SUVA water, aluminum oxide and iron oxide membrane surfaces behaved similarly in terms of NOM rejection. There were no interactions among phenol and NOM fractions and their rejections by aluminum oxide or iron oxide surfaces of the ceramic membranes were not affected by each other. Pore size exclusion mechanism played minor role in the rejection of phenol; the major rejection mechanism was electrostatic repulsion, depending on water pH. Compared with the uncoated membrane, membrane coating did not change membrane permeability. Coated iron oxides were stable and iron leaking was not observed. Coating tight-UF ceramic membranes with iron oxide layers may improve NOM rejections during drinking water treatment, especially in waters with high SUVA values.