Removal of organic dye in the hybrid photocatalysis/membrane processes system

The removal of azo dye Acid Red 18 in hybrid photocatalysis/membrane processes systems was investigated. The photocatalytic reactions were conducted in the reactor with photocatalyst suspended in the solution. The reaction solution was recirculated through the ultrafiltration system. A commercially available titanium dioxide (Aeroxide® P25, Degussa, Germany) was used as a photocatalyst. The solution after the photocatalytic/UF reaction was applied as the feed for the membrane distillation process. The changes of various parameters, including the concentration of the dye, pH and the conductivity of the solution, TOC and TDS content were analyzed during the process.

It was found that azo dye Acid Red 18 could be successfully decolourised in the hybrid photocatalysis/UF system. The catalyst particles were retained in the feed solution by means of the ultrafiltration membrane so the obtained permeate was free of TiO₂. The application of ultrafiltration together with the photocatalytic process results in the separation of photocatalyst from the treated solution but does not give the complete removal of organic matter from the reaction mixture. Membrane distillation applied with the permeate after the photocatalysis/UF process as a feed gives a complete separation of TOC from the treated solution and the obtained product is practically pure water.