Although zero-valent iron represents a promising approach for reduction of nitrate (NO3) in water, its application in concentrated nitrate is limited by surface passivation. In this study, an alternative approach using in situ synthesized zero-valent copper (Cu0) produced by borohydride (NaBH4) was investigated. Complete reduction was observed within 55 min by reacting 677 mg-N/L of NO3 with CuO (0.312 g/L) and NaBH4 (4.16 g/L) at 60 °C. The pseudo-first-order rate constant was 0.059 min−1, and it increased threefold when the CuO dose was increased to 1.24 g/L. Increasing the NaBH4 dose produced less nitrite (NO2) throughout the experiments, indicating that it is the primary agent for reducing NO2. The initial pH exerted a significant effect on the reaction rate, and NO3 was rapidly reduced when the initial pH was less than 4. Based on the research findings, possible reaction pathways for NO3 reduction by Cu0 are proposed in this work.

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