Reduction of concentrated nitrate by using in situ synthesized zero-valent copper Available to Purchase

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.