Biodegradability enhancement of azo dye Direct Orange-26 using UV/Fenton-like process: optimization using response surface methodology

In the present study, the enhancement of biodegradability of Direct Orange-26 (azo dye) in aqueous solution by photo-Fenton-like process and nano-Fe 2 O 3 as catalyst was investigated. The effects of initial pH, reaction time, initial concentration of nano-Fe 2 O 3 , and H 2 O 2 dosage on the biochemical oxygen demand (BOD 5 )/chemical oxygen demand (COD) ratio were studied in batch process using response surface methodology. The analysis of variance suggested that the optimal conditions for enhancement of biodegradability of azo dye solution to be counted as a biodegradable effluent are as follows: nano-Fe 2 O 3 concentration of 0.23 g L -1 , H 2 O 2 concentration of 64 mM, pH of 7.5, and the reaction time of 21.66 min. The BOD 5 /COD ratio at optimal condition was predicted to be 0.50 and confirmed by the experimental study. A good agreement between the model prediction and experimental results confirms the reliability of the developed model for BOD 5 /COD ratio.