Removal of humic acid foulant from ultrafiltration membrane surface using photocatalytic oxidation process

The experimental results indicated that without the TiO(2) particles and PCO treatment, the permeate flux of ultrafiltration (UF) membrane declined to 40% of the initial permeate flux after El hours filtration. Feeding the humic acid solution with TiO(2) particles dosage of 1 g/L with calcium ions into UF membrane, after the same filtration time and PCO reaction at 120 minutes, the permeate flux was increased to about 90% of the initial permeate flux. At longer PCO reaction times, a better water quality of UF permeate was observed. It has been found that with the coexistence of calcium ions in humic acid solution, the smaller molecular fragments of humic acid (HA) generated by PCO reaction may be transferred to the surface of TiO(2) by means of adsorption. The humic acid adsorption by TiO(2) in the presence of Ca(2+) is also pH dependent. The adsorption rates were 21.0, 14.9 and 10.8 ppmTOC/gTiO(2) for pH value of 4, 7 and 10 respectively. The combination of effects of PCO mineralization of humic acid into CO(2) and adsorption of humic acid by TiO(2) through the forming of HA-Ca(2+)-TiO(2) aggregate particles were responsible for the removal of humic acid foulant from UF membrane surface.