Degradation of H-acid by combined photocatalysis and ozonation processes

The combination of TiO2-assisted photocatalysis and ozonation (TiO2/UV/O3) to degrade H-acid (1-amino-8-naphthol-3,6-disulfonic acid) was investigated. It was observed that a synergistic effect occurs in this process. The effects of O3 dosage, initial solution pH and initial concentration of H-acid on the efficiency of the process were also studied. The results showed that COD (chemical oxygen demand) removal rate increased with increasing O3 dosage whereas initial solution pH had little effect. An H-acid solution of 500–2000 mg/L could be efficiently degraded using TiO2/UV/O3. The intermediates formed in the early phase of degradation were studied using UV–vis absorption spectra, IC, HPLC–MS and IR; four possible intermediates, 1-amino-5,7,8-trihydroxynaphthalene-3,6-disulfonic acid, 1-amino-2,4,5,8-tetrahydroxynaphthalene-3,6-disulfonic acid, 8-hydroxy-1,2-naphthoquinone-3,6-disulfonic acid and 8-hydroxy-1,4-naphthoquinone-3,6-disulfonic acid, were proposed.