A hybrid photocatalysis and ceramic membrane filtration process for humic acid degradation: Effect of pore size and transmembrane pressure

A hybrid photocatalysis with ceramic membrane filtration system is demonstrated for degradation of humic acids (HAs), which are typical refractory components of natural organic matter (NOM) present in water and wastewater. More specifically, the combination of chemical oxidation photocatalysis process with physical separation via a ceramic membrane filtration was explored. The effects of operating parameters such as transmembrane pressure and the membrane pore size on the permeate flux and organic removal was investigated. The interaction between the two solutes in the system, humic acids and TiO2 photocatalyst, played an important role in the observed flux decline during ceramic ultrafiltration (UF) and microfiltration (MF). Results showed that the MF membrane showed flux rates that were about 30% lower than the ones achieved with UF membranes. The dissolved organic carbon (DOC) removal was found to be higher in UF membrane (> 70%) compared to MF membrane (50%). Finally from the liquid chromatography (LC) analysis showed that after photocatalytic treatment, there is a change in the molecular weight distribution of the organic compounds and preferential adsorption of those compounds by TiO2 results in different fouling mechanisms in UF and MF membranes. It can be concluded that the use of ceramic membrane not only acts as a barrier in recovering the TiO2 photocatalyst but also assists in DOC reduction.