Efficiency and toxicity: comparison between the Fenton and electrochemical processes

Abstract

This study aimed to determine the best method to treat a textile effluent containing the dye basic blue 99 (BB). Treatments by the electrochemical and the Fenton processes were compared by means of a 2(3) experimental design, and the interaction of experimental conditions for BB oxidation were determined. The electrochemical treatment gave better results in the presence of NaCl as electrolyte and high current density (30 mA cm(-2)); the Fenton reaction provided better results at H2O2 and Fe(2+) concentrations of 10 mg L(-1) and 0.5 mmol L(-1), respectively. Electrochemical treatment was 23 times faster than the Fenton reaction because formation of chlorinated species during electrooxidation significantly contributed to dye oxidation. Although the electrochemical process was more efficient, the resulting treated effluent was more toxic to Lactuca sativa germination and growth, which indicated some biotoxicity. Results demonstrated that both processes efficiently remediated effluents containing the dye BB, but they need to be combined with other processes to ensure complete adequacy of the effluent for disposal.

Electro-Oxidation in Combination with Biological Processes for Removal of Persistent Pollutants in Wastewater: A Review

“…As mentioned before, indirect oxidation involves the generation of by-products from chlorine (equation 3-6) whose presence in EO is one of the most significant factors (along with electrolysis time and current) in the removal of pollutants; the higher the concentration of Clions, the greater the efficiency in the removal of organic matter and POPs/EPs. Of course there is an optimum that can be found as a ratio COD/[Cl -] in which the removal of organic compounds will no longer increase [37,67].…”

“…(5) (6) The presence of Climproves the removal of organic compounds and has been evaluated by many authors. Tavares et al [67] used NaCl (0.2 mol/L) as supporting electrolyte to degrade basic blue 99 dye in 5 min with DSA ® electrodes, unlike the 60 min it took using Na 2 SO 4 (0.2 mol/L) as supporting electrolyte. Similarly, Serrano-Torres et al [68] degraded Diazo dye Congo (99% removal) faster (5 min) using NaCl (0.05 mol/L) compared to HClO 4 , Na 2 SO 4 and H 2 SO 4.…”