Atomically dispersed copper sites on titanium zirconium oxide accelerate the simultaneous oxidative removal of organic carbon and ammonia from landfill leachate

Abstract

Landfill leachate is a refractory wastewater. Low-temperature catalytic air oxidation (LTCAO) has shown considerable potential for leachate treatment owing to its green and simple operation, but the simultaneous removal of chemical oxygen demand (COD) and ammonia from leachate remains challenging. Herein, TiZrO4 @CuSA hollow spheres with high-loading single-atom Cu were synthesized using isovolumic vacuum impregnation and co-calcination methods, and the catalyst was applied to the LTCAO treatment of real leachate. Consequently, the removal rate of UV254 reached 66% at 90 °C within 5 h, while that for COD was 88%. Simultaneously, the NH3/NH4+ (33.5 mg/L, 100 wt%) in the leachate was oxidized to N2 (88.2 wt%), NO2--N (11.0 wt%), and NO3--N (0.3 wt%) owing to the effect of free radicals. The single-atom Cu co-catalyst in TiZrO4 @CuSA exhibited a localized surface plasmon resonance effect at the active center, which could quickly transfer electrons to O2 in water to form O2.− with a high activation efficiency. The degradation products were determined and the deduced pathway was as follows: the bonds joining benzene rings were first broken, and then the ring structure was further opened to produce acetic acid and other simple organic macromolecules, which were finally mineralized to CO2 and H2O.