Degradation of Glyphosate in Water by Electro-Oxidation on Magneli Phase: Application to a Nanofiltration Concentrate

This study evaluates the efficiency of sub-stoichiometric Ti₄O₇ titanium oxide anodes for the electrochemical degradation of glyphosate, a persistent herbicide classified as a probable carcinogen by the World Health Organization. After optimizing the process operating parameters (pH and current density), the mineralization efficiency and fate of degradation by-products of the treated solution were determined using a total organic carbon (TOC) analyzer and HPLC/MS, respectively. The results showed that at pH = 3, glyphosate degradation and mineralization are enhanced by the increased generation of hydroxyl radicals (^●OH) at the anode surface. A current density of 14 mA cm-2 enables complete glyphosate removal with 77.8% mineralization. Compared with boron-doped diamond (BDD), Ti4O7 shows close performance for treatment of a concentrated glyphosate solution (0.41 mM), obtained after nanofiltration of a synthetic ionic solution (0.1 mM glyphosate), carried out using an NF-270 membrane at a conversion rate (Y) of 80%. At 10 mA cm-2 for 8 h, Ti4O7 achieved 81.3% mineralization with an energy consumption of 6.09 kWh g-1 TOC, compared with 90.5% for BDD at 5.48 kWh g-1 TOC. Despite a slight yield gap, Ti4O7 demonstrates notable efficiency under demanding conditions, suggesting its potential as a cost-effective alternative to BDD for glyphosate electro-oxidation.