Copper nanoparticles/graphene modified green rusts for debromination of tetrabromobisphenol A: Enhanced galvanic effect, electron transfer and adsorption

The combined effect of copper nanoparticles (Cu NPs) and reduced graphene oxide (RGO) on the reactivity of green rust (GR) towards reductive debromination of tetrabromobisphenol (TBBPA) has been systematically investigated. The removal efficiency of TBBPA increased from 28.78% to 44.70% and the pseudo first-order rate constant (k(obs)) increased from 0.002 min(-1) to 0.004 min(-1) when the content of Cu NPs in GR(SO4)-Cu NPs increased from 0% to 0.5%. Cu NPs enhanced the reductive reactivity of GR via formation of a galvanic cell and Cu-0/Cu+ redox cycle. The adsorption capacity of RGO towards TBBPA was 13.75 mg/g. The pseudo first-order rate constant for TBBPA removal increased from 0.0341 min(-1) to 0.0866 min(-1) when the RGO content increased from 0 to 2% in GR-Cu NPs-RGO. RGO enhanced the debromination efficiency via enhancing the adsorption of TBBPA and accelerating electron transfer amongst GR, Cu NPs and TBBPA. The increased corrosion current demonstrates the enhanced electron transfer by RGO in GR-Cu NPs galvanic cell. Six-electron transfer process of TBBPA reduction was revealed by rotating disk electrode analysis, which was in line with the final debromination products (Mono-BPA) determined by ion chromatography and liquid chromatography-mass spectrometry. (C) 2019 Elsevier B.V. All rights reserved.