The assessment of basic blue 41 textile dye decolorisation using the Fenton process: response surface methodology optimisation and toxicity evaluation

The biochemical biomarkers (Catalase (CAT), glutathione s-transferase (GST), cytochrome P4501A1 (CYP1A1450) activities and glutathione (GSH), malondialdehyde (MDA) levels) of D. polymorpha exposed to the basic blue 41 (BB41) solutions for 24 and 96 h before and after the Fenton process (FTP) were evaluated to investigate the efficiency of the FTP. The optimum conditions for the removal of BB41 were set using central composite design (CCD), which is a response surface methodology (RSM) module in the Design-Expert® software. The optimal conditions were found to be 27.87 min, 3.49 mg/L, and 0.04 for reaction time, initial BB41 concentration, and Fe2+/H2O2 molar ratio, respectively, resulting in maximum (99%) removal efficiency. After FTP, the MDA and GSH levels decreased significantly during the 24 and 96 h. CAT activities were increased after treatment. No statistically significant changes were observed in the CYP1A1 levels after FTP. GST activities decreased during 24 h but increased during 96 h after FTP. CYP1A1450, catalase, GST activities and MDA, GSH levels of D. polymorpha are useful biomarkers to evaluate the efficiency of FTP. This study suggests that BB41 dye must be further treated after the FTP to minimise the ecotoxicological risk.