Printing ink effluent remediation: A comparison between electrochemical and Fenton treatments

This work uses a 22 experimental design to describe remediation of wastewater samples containing printing inks by an electrochemical process or the Fenton reaction. The electrochemical procedures were carried out in the presence of Na2SO4 (0.2 mol L−1, as electrolyte) with or without NaCl (1 mmol L−1) under a current density of 15 or 30 mA cm-2. During the Fenton assays, the effects of Fe2+ and H2O2 concentrations were investigated (0.3 or 0.5 mmol L−1 for Fe2+ and 50 or 100 mg L−1 for H2O2). Treatment efficiency was monitored by UV–vis spectrophotometry and chemical oxygen demand. Both the Fenton reaction and the electrochemical process conducted under a current density of 30 mA cm-2 in the presence of chloride (1 mmol L−1 NaCl) suppressed the organic load (by about 34% and 90%, respectively). The Fenton reaction was less efficient than the electrochemical process, regardless of the concentration of the Fenton reagents. Raw effluent, effluent treated by the Fenton reaction, and effluent treated by the electrochemical process in the presence of chloride showed high ecotoxicity. In the case of the Fenton reaction, ecotoxicity was due to the low amount of remediated pollutants. As for the electrochemical process, ecotoxicity was possibly due to the presence of chlorinated species, which are highly oxidant.