Photocatalytic oxidation of aquatic humic substances using TiO ₂/UV in a rotating photoreactor

Applicability of a rotating reactor for photocatalytic oxidation of humic substances extracted from the Han River in Seoul, Korea (Han-HS) was investigated. Because air blowing for complete dispersion of TiO₂ photocatalysts could inhibit ultraviolet (UV)-irradiation between UV lamps and photocatalysts by air bubbles, a rotating photocatalytic reactor with four baffles was used for better UV-irradiation in this study. Han-HS was extracted and treated with UV-irradiation. Because Han-HS is different from other commercial humic materials (e.g. Aldrich Humic acid and International Humic Substance Society NOM), structural spectroscopic analyses were conducted by FT-IR and ¹³C-NMR. Immobilized TiO₂ coated on hollow beads was used to separate and recover the photocatalyst. During two hours of UV-irradiation, absorbance at 254 nm (UV₂₅₄) and total organic carbon (TOC) content were monitored. Photocatalytic oxidation efficiencies of different wavelengths of UV lamps (254 nm and 352 nm) were also compared and raw and pre-chlorinated waters of the Han River were used to evaluate the applicability for water treatment.