Enhancing the dioxygen activation for arsenic removal by Cu0 nano-shell-decorated nZVI: Synergistic effects and mechanisms

[Display omitted] •Ultrathin Cu0 shell was decorated on the surface of nZVI core.•The adsorption and oxidation performance for arsenic was significantly improved.•The loaded Cu0 shell realized the enhancement of electron utilization.•CuI accelerated the generation of superoxide radical to produce various ROSs. Using copper and/or iron based nanomaterial to activate dioxygen to produce free radicals is an alternative and environmental friendly technique, but the low conversion efficiency of oxygen and the rate-limiting step of superoxide radical generation limit current application. In present work, Cu0 nano-shell-decorated nZVI (CFNs) was synthesized and employed to enhance the activation of oxygen for the removal of arsenic at circumneutral pH. The adsorption and oxidation pathways of arsenic were investigated by determination of arsenic distribution and radical scavenger methods. The results showed that the removal of arsenic by CFNs involved the initial step of AsIII adsorption by ferrihydrite followed by the oxidation of AsIII by hydroxyl radical (OHabs) and superoxide radical (O2−abs) radicals. In the presence of oxygen, the removal capacity of CFNs was improved twice than that of conventional nZVI (i.e. 453 mg/g and 263 mg/g, respectively). We inferred that CuI in-situ generated in heterogeneous catalysis was of increasing importance and the O2–abs produced from the activation of dioxygen was regarded as the key factor in the generation of H2O2 at pH 7. The enhancement of CuI generation mainly because of: (i) the facial loading of Cu0 shell accelerated the generation of CuI, (ii) reductive Fe0 core contributed to the regeneration of CuI, and (iii) the generation of ferrihydrite with high specific surface area favored the adsorption of oxygen. Hence, CFNs enhanced the electron transfer between CuI/FeII and O2, increased the utilization efficiency of oxidants and improved the effectiveness of the functional nanoparticles for environmental applications.