Performance of L-Cu&Mn-nZVFe@B nanomaterial on nitrate selective reduction under UV irradiation and persulfate activation in the presence of oxalic acid

Highlights: • Novel L-Cu&Mn-nZVI@B nanomaterial was synthesized and applied for nitrate reduction. • The coexistence of Cu₂O-MnO₂ can improve photocatalytic performance. • Deposition of Mn could accelerate the generation of CO₂- through the activation of persulfate. • The nitrate removal efficiency by S₂O₈^2-/UV/L-Cu&Mn-nZVI@B/H₂C₂O₄ system was near 100 %. • The N₂ selectivity of nitrate reduction by S₂O₈²⁻/UV/L-Cu&Mn-nZVI@B/H₂C₂O₄ system was 81.57 %. A novel nanomaterial (L-Cu&Mn-nZVFe@B) was synthesized and was applied to nitrate selective reduction under UV irradiation and persulfate activation in the presence of oxalic acid. Results denoted the deposition of copper could prompt the nitrate conversion and improve the nitrate conversion significantly. The high nitrate conversion was on account of the formation of galvanic cells accelerating the generation of electrons, in which Fe° acted as anode and Cu° acted as cathode. Meanwhile, the coexistence of Cu₂O and MnO₂ exhibited excellent photocatalytic performance with the obvious improvement of N₂ selectivity because of the formation of heterojunction could boost the generation of CO₂⁻. Furthermore, the deposition of manganese could also accelerate the generation of CO₂⁻ through the activation of persulfate. The conversion of NO₃⁻ was almost 100 % and the N₂ selectivity could reach 81.57 % by the S₂O₈^2―/UV/L-Cu&Mn-nZVFe@B/H₂C₂O₄ system when the initial nitrate concentration was 100 mg /L, the L-Cu&Mn-nZVFe@B dosage was 6.0 g/L, the H₂C₂O₄ dosage was 15 mmol/L, pH was 5.0, the reaction time was 100 min under 25 °C. Research provides an alternative approach for selective reduction nitrate into nitrogen.