Advanced reduction of Cr(VI) in real chrome-plating wastewater using a VUV photoreactor: Batch and continuous-flow experiments

• Photoreduction of Cr(VI) in real wastewater was examined using a VUV reactor.
• Complete reduction of different concentrations of Cr(VI) was attained without additives.
• VUV reactor reduced Cr(VI) at a much greater rate than photocatalysis.
• VUV reactor operated in continuous mode at different HRTs for Cr(VI) reduction.
• VUV reactor introduced as an appropriate technology for reduction of Cr(VI).

Performance of a VUV photoreactor was investigated for the reduction of Cr(VI) in real chrome-plating wastewater. The effect of wastewater pH, initial Cr(VI) concentration, organic reductant, air/N2 gas blowing and reaction time was investigated for a decrease Cr(VI) in batch experiments. The decrease in Cr(VI) was examined using a VUV photoreactor in continuous-flow mode as a function of hydraulic retention time (HRT). Maximum photoreduction of Cr(VI) obtained in batch tests at acidic pH of 1.8 with N2 blowing. The presence of methanol accelerated reduction of Cr(VI). Cr(VI) at initial concentrations of 10, 20, 30, 50 and 100 mg/L was reduced completely in the batch VUV photoreactor at reaction times of 2, 10, 12, 16 and 25 min, respectively. The VUV photoreactor also operated in continuous-flow mode, where 91.7% of 30 mg/L Cr(VI) reduced in a HRT of 6 min. The VUV photoreactor is an efficient and practicable technology for reduction of Cr(VI) to treat Cr(VI)-laden streams.