Enhanced electrochemical degradation of microcystin-lysine-arginine (MC-LR) using novel nickel oxide anodes in real water matrices.

Microcystin-lysine-arginine (MC-LR) is a potent hepatotoxin linked to liver and colon cancer, requiring effective removal from water sources. Electrochemical oxidation (EO) offers a promising alternative for in situ degradation of MC-LR. In this study, a novel nickel (II) oxide (NiO) material was synthesized via thermal annealing at 600 °C and evaluated for the electrochemical degradation of MC-LR in both buffered solutions and real water matrices. Using 0.1 M phosphate buffer (PB) solution (pH 7, EC = 16.34 mS cm-1), the NiO anode achieved complete degradation of 20 ppb MC-LR within 2 h at a current density of 5 mA cm-2, corresponding to a rate constant of 0.021 min-1 and low energy consumption (0.12 kWh m-3). In real water samples with enhanced ionic strength, including tap water (pH 7, EC = 10.34 mS cm-1, 2.0 mg L-1 DOC) and lake water (pH 7, EC = 10 mS cm-1, 11.2 mg L-1 DOC), the NiO electrode achieved 62% and 42% removal of 20 ppb MC-LR within 4 h, with degradation rates of 0.0041 and 0.0023 min-1 and energy demands of 1.08 and 1.20 kWh m-3, respectively. Elevated pH and dissolved organic carbon (DOC) levels were found to suppress degradation efficiency, emphasizing the importance of water chemistry in practical applications. The NiO anode exhibited operational stability over three days, confirming its potential as a durable, energy-efficient, and practical material for MC-LR removal in water treatment systems. Overall, this study demonstrates that NiO is a cost-effective, stable, and energy-efficient anode material for the EO of MC-LR, highlighting its potential for practical cyanotoxin control in water treatment systems.