Microwave assisted photocatalytic degradation of high concentration azo dye Reactive Brilliant Red X-3B with microwave electrodeless lamp as light source

A device for microwave assisted photocatalysis (TiO2/MWL) was described based on a modified domestic microwave oven that incorporated a novel microwave electrodeless lamp as the source of UV–vis irradiation to photodegrade environmental pollutants of high concentration in aqueous media. The performance of this device was examined using the photodegradation of azo dye Reactive Brilliant Red X-3B driven by a coupled UV–vis/microwave irradiation in an aqueous TiO2 dispersion. The coupled UV–vis/microwave irradiation led to effective degradation of higher concentration dyes in TiO2/MWL than in conventional photocatalysis. Higher photodegradation efficiency, higher rate constant (k) of surface reaction between dyes and hydroxyl radicals and slighter influence of the initial dye concentration on photodegradation were found in TiO2/MWL. For 400 mg/L X-3B, removal of color and total organic carbon (TOC) reached 100% and 65% after 180 min, respectively. Meanwhile, the biodegradability of dye solution indicated by the value of BOD5/COD increased from initial 0.03 to 0.35 which indicated that TiO2/MWL could be used as a pre-treatment process of biotreatment as well. Moreover, photodegradation rate could be enhanced evidently in TiO2/MWL by inorganic oxidizing species (H2O2, Na2S2O8 and Fe(NO3)3).