Advanced electrochemical oxidation applied to benzodiazepine and carbamazepine removal: Aqueous matrix effects and neurotoxicity assessments employing rat hippocampus neuronal activity

Abstract

Benzodiazepines and carbamazepine are mental disorder treatment-related contaminants of emerging concern (CECs) routinely detected in water bodies. Electrochemical oxidation (EO) processes have been proven effective in reducing CECs levels, although the toxic effects of residual compounds formed after EO are still scarcely studied. Herein, ultrapure water (UP), surface water (SW), municipal wastewater (MWW), and industrial pharmaceutical wastewater (IWW) were spiked with four benzodiazepines (alprazolam, clonazepam, diazepam, lorazepam) and carbamazepine (100 μg L−1 each) and treated by an EO process employing two electrodes: a platinum-coated titanium (Ti/Pt) and a boron-doped diamond (BDD). Neurotoxicity tests were performed by exposing rat hippocampus slices to EO-treated waters to investigate the effects of residual compounds on neuronal activity. The EO results indicate that both electrodes were efficient in completely removing the studied drugs from UP and SW, but that <50 % removal was achieved for MWW. For IWW, total organic carbon (up to 71 %) and total nitrogen (up to 82 %) removals were achieved at 1000 A m−2. UP exposure significantly reduced ROS production, likely due to the presence of transformation by-products. SW and MWW EO-treated waters led to slight neurotoxicity. Decreased neurotoxicity was mainly observed for the IWW after EO using both the BDD and Ti/Pt anodes. A ROS production evaluation following the application of several untreated effluent cycles demonstrated that long-term effects may alter cell functionality and that recovery responses decrease over time.