Coupling photocatalytic and electrocatalytic oxidation towards simultaneous removal of humic acid and ammonia−nitrogen in landscape water

Aiming to bring photocatalytic and electrocatalytic oxidation processes into solving practical issue of organics and ammonia−nitrogen pollution in landscape water that resulting in algae bloom and eutrophication, this work firstly investigates photocatalytic oxidation of humic acid and electrochemical oxidation of ammonia upon optimization of each process parameters, respectively. The platinum modified titania (Pt/TiO2) exhibits improved activity than pure titania and CuOx, MnOx and NiOx modified titania for decomposition of humic acid. As an application−oriented study, this work has developed a simple and effective brushing and annealing method for immobilization of TiO2 and Pt/TiO2 onto ceramic foam for further application. In addition, the RuO2–IrO2/Ti electrode presents the best electrocatalytic activity compared with RuO2/Ti and IrO2/Ti electrodes in terms of ammonia oxidation, and the ammonia conversion pathways have been studied. Lastly, an integrated and enlarged reactor system employing optimized photocatalytic ceramic foam and stable electrodes has been developed for simultaneous oxidation of humic acid and ammonia−nitrogen in water circulated flow condition, based on cooperative production of reactive oxidant species between photocatalysis and electrocatalysis. The results show that coupled photocatalytic and electrocatalytic oxidation is a promising approach for treatment of organic matter and inorganic ammonia nitrogen in landscape water.