Photocatalytic reduction of hexavalent chromium [Cr(VI)] was investigated to evaluate effectiveness for removing all chromium species from drinking and industrial waters. Deionized and tap water experiments were performed using a system that recirculates TiO2 through an integrated process consisting of ultraviolet (UV) lamps and a ceramic membrane. Hexavalent and total chromium concentrations were simultaneously reduced during treatment. Cr(VI) removal gradually increased with higher energy input and TiO2 dosage, achieving greater than 90% removal for a 1 g/L dose of TiO2. Cr(VI) was photochemically reduced to Cr(III) on the surface of TiO2, where the Cr persisted as a precipitate. Upon further irradiation, Cr(III) could be reoxidized to Cr(VI). High-volume flow-through experiments indicated significantly diminished chromium removal due to catalyst fouling during continuous catalyst use. To greater extents in tap water than in DI water, photoaggregation of the TiO2 catalyst was evidenced by increased particle size. This photoaggregation effect was further supported by decreased breakthrough of TiO2 with increased irradiation intensity.
- Hexavalent chromium
- Titanium dioxide
ASJC Scopus subject areas
- Environmental Chemistry
- Waste Management and Disposal