Performance of an integrated membrane photocatalytic reactor for the removal of Reactive Black 5

Abstract

Removal of synthetic dyes from wastewater is extremely important from an environmental perspective. Heterogeneous photocatalytic technique using UV/TiO 2 slurry reactor system has demonstrated to be very effective in treating toxic and complex organic dyes. Advanced membrane separation technique can easily solve an important issue of catalyst separation, while the separated catalyst can be reused in a slurry photocatalytic reactor and operated continuously. In this study, a membrane photocatalytic reactor (MPR) was fabricated by integrating a novel flat plate PTFE membrane module along with a slurry photoreactor. The performance of MPR was evaluated for the mineralization of Reactive Black 5 (RB5) and the efficiency of catalyst recycling and reuse were studied using batch and long-term continuous experiments. The results from this study showed that nearly 99.99% color removal and 75–82% TOC and COD removal can be achieved easily by photocatalysis, depending on the initial operating condition and exposure time. Moreover, it was observed that the initial concentration of RB5 plays a significant role in color removal, i.e., low initial concentration giving faster color and TOC removal. The photocatalytic mineralization of RB5 caused a reduction in the TOC and the release of mineralized ionic products such as sulfate, nitrate, nitrite and ammonia. The result showed that the color removal of RB5 dye follows pseudo-first-order kinetics and the rate constant decreases marginally with an increase in the initial dye concentration. Furthermore, during continuous, long-term operations, the membrane module was able to separate and recycle the catalyst effectively within reactor, and the catalyst was also reused without much loss in dye degradation efficiency.