Experimental study on supercritical water oxidation of CI Reactive Orange7 dye wastewater using response surface methodology

Supercritical water oxidation of azo dye CI Reactive Orange7 solution was investigated in a batch reactor. Response surface methodology was employed for the experimental design. Quadratic polynomial equations were established based on the results of the experiments. Optimisation of the process was then conducted in accordance with the simulated equations. The results show that removal of chemical oxygen demtotal organic carbon and total nitrogen can be achieved up to 99, 95 and 69%, respectively, and the predictive data were in reasonable agreement with the experimental results. It seems that response surface methodology is useful and feasible for the optimisation of CI Reactive Orange7 dye wastewater supercritical water oxidation processing. The gas chromatography/mass spectrometry analysis results show that a large amount of 2,4-pentadienenitrile with diazo formed during the CI Reactive Orange7 supercritical water oxidation reaction, which suggested that the azo firstly reacted to the diazo, and then converted into the final product of nitrogen.