Active chlorine mediated ammonia oxidation in an electrified SnO2–Sb filter: Reactivity, mechanisms and response to matrix effects

Ammonia pollution control has gained increasing attention as a result of the existential threat to the environment. The electrochemical advanced oxidation process has demonstrated to be an attractive and environmentally benign platform for aqueous ammonia removal because it only requires electricity and water as a clean “reagent”. Herein, we developed a porous SnO 2 –Sb filter toward high-efficient ammonia conversion. Despite the introduction of enhanced convection, chlorine-mediated ammonia oxidation dominated the reaction mechanism of the electrified SnO 2 –Sb filter at circumneutral pH. At an extremely short hydraulic contact time (1.0–5.1 min), ammonia was primarily oxidized to N 2 with no chloramines detected. Matrix effect assays showed that the chloride–to–ammonia ratio was vital to determine the removal rate and product selectivity. A pH buffer, HCO 3 − , might prompt ammonia removal whilst inhibiting chlorate formation. In contrast, the ammonia removal performance of the SnO 2 –Sb filter deteriorated in the presence of dissolved organic matter ( e.g. , humic acid). The matrix effects significantly influenced the process efficiency to treat municipal sewage and lake water. The results of this study can advance our understanding of electrochemical ammonia oxidation and provide insight into the effective implementation and optimization of the flow-through process.