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 TiO<inf>2</inf> 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 TiO<inf>2</inf> dosage, achieving greater than 90% removal for a 1 g/L dose of TiO<inf>2</inf>. Cr(VI) was photochemically reduced to Cr(III) on the surface of TiO<inf>2</inf>, 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 TiO<inf>2</inf> catalyst was evidenced by increased particle size. This photoaggregation effect was further supported by decreased breakthrough of TiO<inf>2</inf> with increased irradiation intensity.
- Hexavalent chromium
- Titanium dioxide
ASJC Scopus subject areas
- Waste Management and Disposal
- Environmental Chemistry