Effectiveness of photodecomposition of an azo dye on a novel anatase-phase TiO2 and two commercial photocatalysts in a photocatalytic membrane reactor (PMR)

An application of a newly prepared TiO2 having anatase phase (A-700-1h) for decomposition of azo dye Acid Red 18 (AR18) in a photocatalytic membrane reactor (PMR), coupling photocatalysis and membrane distillation (MD) was investigated. The effectiveness of decomposition of the model dye using two commercially available TiO2 photocatalysts – ST-01 and P25 was also determined in order to compare the results. The A-700-1h catalyst was prepared from a crude amorphous TiO2 obtained directly from the production line (sulfate technology) at the Chemical Factory “Police” (Poland) by calcination for 1 h at 700 °C in air. The hybrid photocatalysis–MD process was conducted in a laboratory-scale installation with a capillary module equipped with polypropylene membranes. It was found that the initial degradation rate r0 of AR18 using the A-700-1h catalyst was 49–64% higher than in case of anatase ST-01. Moreover, the effectiveness of decolorization of the dye solution at the A-700-1h loading of 0.5 g/dm3 determined on the basis of r0 value was only ca. 8% lower compared to the value determined for the P25 photocatalyst. Taking into account the composition of permeate it was found that only a small amount of by-products of dye photodecomposition was transported through the MD membrane. Moreover, a complete retention of the model dye was observed.