Electrochemical oxidation of hydrothermal liquefaction aqueous phase: optimized degradation, hydrogen generation, and...

Hydrothermal liquefaction aqueous phase (HTL-AP) contains complex organics and nitrogen compounds that challenge conventional wastewater treatment. Electrochemical oxidation (EO) was employed to simultaneously degrade organics and generate hydrogen. A Taguchi L9 orthogonal design optimized current density, dilution rate, and chloride ion (Cl^-) concentration. Under optimized conditions, 77.48 % COD removal rate and a high-purity (>95 %) hydrogen yield of 1942.24 mL/g COD were achieved, with high current efficiency (CE) and energy efficiency (EE). Current density and dilution rate were dominant factors of COD removal rate and hydrogen yield. Moderate Cl^- levels enhance oxidation via reactive chlorine species (RCS), whereas excessive Cl^- causes electrode passivation and lowers CE. During EO, alcohols were selectively oxidized to carboxylic acids, and nitrogenous organics transformed into nitrates and ammonia, achieving green removal and resource recovery. This study demonstrates an energy-efficient and scalable EO strategy for HTL-AP valorization, integrating pollutant degradation, hydrogen production, and resource recovery.