Rapid and effective nitrate reduction over wide pH range using CuxO-CNT with the presence of KBH4: The role of in situ produced hydrogen and zero-valent copper

CNTs-Cu x O prepared by impregnation was used with KBH 4 to reduce NO 3 – -N as the first step. CNTs-Cu x O was characterized by SEM, EDS-mapping, TEM, XRD and XPS . The NO 3 – -N reduction batch experiment showed that 100% of NO 3 – -N removal efficiency was achieved in < 10 min with the initial pH of 3.0, 5.0 and 7.0, NO 3 – -N concentration of 30 mg(N)/L, CNTs- Cu x O dosage of 3 g/L and KBH 4 concentration of 3 mmol/L. At the initial pH of 9.0, NO 3 – -N was completely removed in 15 min. The main product of the first step reaction was NO 2 – -N, which was accumulated in the solution and rapidly reduced to N 2 by NH 2 SO 3 H as the second step. The reusability of CNTs-Cu x O was evaluated and the experiment result showed that 96% of NO 3 – -N removal efficiency was achieved in 10 min after CNTs-Cu x O was reused for 5 cycles of reaction. Moreover, the Cu 2+ dissolution was kept monitored for the reaction system, and the analysis result showed that there was no Cu 2+ leaching for all cycles of reutilization.