Apparent and true mineralization during combined electro-oxidation and electro-coagulation on stainless steel anode

Present study is a novel attempt to experimentally verify that electrochemical treatment of organic pollutants on stainless steel (SS) anode is a combination of electro-oxidation (EO) and electro-coagulation (EC) with quantitative estimation of individual contributions of the two mechanisms. Target organic pollutants, metformin HCl (MET-HCl) and lamotrigine (LAM), were electrochemically treated with SS anode for this purpose. Experiments were designed using central composite rotatable design (CCRD) to assess the effect of current density (CD) and supporting electrolyte concentration (SEC) as independent process parameters. Under all conditions, the process was experimentally verified to be a combination of EO and EC. For MET-HCl, true mineralization (TM) as a result of EO contribution varied between 50.13% and 66.64%. EO contribution and resulting TM for LAM ranged from 37.5% to 61.83%. EC contributed 30.6%-31.84% towards MET-HCl remediation causing the TOC to be transferred from the liquid to the sludge produced (SP). EC contribution was 23.68%-35.89% for LAM remediation. Thus, apparent mineralization (AM), the sum of EO and EC contributions, ranged from 80.63% to 97.79% for MET-HCl and 61.18% to 96.82% for LAM.Process parameters were statistically optimized using response surface methodology (RSM) to simultaneously maximize TM and AM with minimal energy consumption and maximal current efficiency. The optimized conditions were 0.83 mA/cm(2) CD and 86.66 ppm SEC for MET-HCl. The corresponding values were 1.31 mA/cm(2) CD and 79.51 ppm SEC for LAM.