Diclofenac degradation by activating peroxydisulfate via well-dispersed GO/Cu2O nano-composite

Abstract

Owing to high treatment efficiency under neutral condition and no extra energy required, copper-mediated activation of persulfate (PS) has been widely used for the degradation of refractory organic pollutants in water. The dispersion stability of copper nanoparticle in water, however, remains a great challenge. Meanwhile, chemical oxidative modification of graphene oxide (GO) can improve the dispersion stability of GO in water. In this paper, cuprous oxide (Cu₂O) was deposited on the surface of GO. GO/Cu₂O nano-composites with different mass ratios, i.e., m(GO):m(Cu₂O) of 1:2, 1:5, 1:10, and 1:25, were prepared. When m(GO):m(Cu₂O) was 1:2, the amount of GO/Cu₂O nano-composite was 1.00 g/L and C_PDS:C_DCF was 15:1, and the catalytic degradation rate of diclofenac (DCF) was up to 90%. Corresponding physicochemical properties of the resulting samples were comprehensively characterized by using SEM, TEM, XRD, Raman, FT-IR, and XPS. DCF degradation by activating peroxydisulfate (PDS) via GO/Cu₂O nano-composite was also investigated in detail. It is found that the synergistic effect, namely GO adsorption and multivalent copper ion electron transfer, makes GO/Cu₂O nano-composite reveal higher reactivity. Moreover, GO/Cu₂O nano-composite possesses good stability in consecutive cycling test. EPR analyses shows that ·OH and SO₄^·- radicals are involved in DCF degradation. It is indicated that the DCF degradation process contain hydroxylation and the cleavage of C-N bond, which is explored by GC-MS. In our research, well-dispersed GO/Cu₂O nano-composite with high capacity and good cycling stability was fabricated successfully. Compared with pure Cu₂O nanoparticle, GO/Cu₂O nano-composite exhibits the better performance for DCF removal. A novel well-dispersed cuprous oxide (Cu₂O) deposited on surface of GO was fabricated with high catalytic performance. Its heterogeneous activation of peroxydisulfate (PDS) for diclofenac (DCF) degradation was investigated. GO/Cu₂O nano-composite was proved high capacity and good cycling stability. Meanwhile, the possible DCF degradation pathway was explored. Compared with pure Cu₂O nanoparticle, GO/Cu₂O nano-composite exhibits better performance for DCF removal.

Keywords: Advanced oxidation processes; Diclofenac degradation pathway; GO/Cu2O nano-composite; Persulfate activation; Water treatment.