Electrochemical oxidation for the rapid degradation of emerging contaminants: Insights into electrolytes and process parameters for phytotoxicity reduction.

Atrazine (ATZ), carbamazepine (CBZ), and sulfamethoxazole (SMX) are contaminants of emerging concern (CECs) commonly detected in water sources, posing a risk to health, sanitation, and the ecosystems. This study evaluates the degradation, mineralization, and phytotoxicity reduction of a solution containing these three CECs using an electrochemical advanced oxidation process (EAOP). Key operational parameters - pH, flow rate (Q), current density (j), and type and concentration of supporting electrolytes (NaCl and NaSO) - were systematically investigated. The results showed that pH had minimal impact on the process. Higher flow rates (250 L h) improved mineralization due to enhanced mass transfer to OH on the anode surface. However, the flow rate had less effect on degradation, as the dominant degradation mechanisms involved chlorine- or sulfate-based oxidants. Current densities of 1 and 10 mA cm produced the most favorable results, leading to efficient degradation and mineralization, along with satisfactory mineralization current efficiency (up to 47 %) and energy consumption values (91,76-3142,88 kW h kg). When NaCl was used as supporting electrolyte, the degradation of CECs was twice as fast as with NaSO, achieving over 88 % degradation in 5 min and 40 % mineralization within 60 min. While chlorinated and sulfate species enhance process efficiency, excessive electrolyte concentration should be avoided to prevent scaling and OH scavenging. Phytotoxicity tests with Allium cepa revealed an unexpected reduction in toxicity in samples treated with NaCl, suggesting that NaSO may be more phytotoxic under the tested conditions.