Enhanced reactivity and mechanisms of copper nanoparticles modified green rust for p-nitrophenol reduction

This paper describes the reduction of p-nitrophenol by green rusts (GRs) interlayered with common inorganic anions (Cl^-, SO₄^2- and CO₃^2-). Modifying of GRs with zero-valent Cu nanoparticles (Cu⁰ NPs) can greatly enhance the reductive reactivity of GRs via the formation of a galvanic couple between the GRs and the Cu⁰ NPs, as confirmed by an increased corrosion current. The direct addition of Cu⁰ NPs excludes the possible formation of less active mono-valent Cu in the GRs/Cu²⁺ system. Oxidation of GRs does not occur upon the addition of Cu⁰ NPs, thus a decline in electron transfer from the oxidized GRs to the Cu⁰ NPs is avoided. The optimum Cu⁰ NPs loading on GR_Cl is 0.5% wt. The GR_Cl/Cu⁰ NPs retains high reactivity in the studied pH range from 7 to 10, while the presence of NO₃^-, PO₄^3-, SO₄^2-, CO₃^2- and humic acid inhibits PNP reduction by the GR_Cl and GR_Cl/Cu⁰ NPs. The GR_Cl/Cu⁰ NPs system is less susceptible to the presence of CO₃^2- and humic acid compared to the pure GR_Cl system due to the migration of the PNP reduction sites from the GRs to the Cu⁰ NPs. This work sheds light on a new strategy for enhancing GR-based materials for use in groundwater remediation.