Integrating photocatalysis and membrane technologies for water treatment.

Removal of organic contaminants in water may sometimes be more easily achieved with a pair rather than with a single unit operation. We explore here the combination of an ambient temperature, chemical oxidation photocatalysis (PC) process with physical separation via a membrane operation, microfiltration (MF), ultrafiltration (UF), or reverse osmosis (RO) using both a conceptual statement and a literature review format. Four configurations are noted and discussed here: (1) PC + MF for catalyst slurry recycle, (2) PC + UF for catalyst slurry and (polymer) reactant recycle, (3) immobilized PC and UF/RO for reactant recycle, and (4) immobilized PC on UF/RO membrane for membrane self-cleaning. Although the literature review is encouraging with respect to plausibility, the paucity of examples indicates a need for substantial effort to fully exploit the suggested possibilities for process development.