Magnetic Fe3O4@CoFe-LDH nanocomposite heterogeneously activated peroxymonosulfate for degradation of azo-dye AO7

Dapeng Sun; Chuang Li; Shengsen Lu; Qingfeng Yang; Chiquan He

doi:10.1039/d1ra02973h

Magnetic Fe₃O₄@CoFe-LDH nanocomposite heterogeneously activated peroxymonosulfate for degradation of azo-dye AO7

RSC Adv. 2021 Jun 7;11(33):20258-20267. doi: 10.1039/d1ra02973h. eCollection 2021 Jun 3.

Authors

Dapeng Sun^{1

2}, Chuang Li^{2

3}, Shengsen Lu^{1

2}, Qingfeng Yang², Chiquan He¹

Affiliations

¹ School of Environmental and Chemical Engineering, Shanghai University Shanghai 200444 P. R. China.
² Green Chemical Engineering Technology Research Centre, Shanghai Advanced Research Institute, Chinese Academy of Sciences Shanghai 201210 P. R. China qfyang2021@163.com.
³ School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences Beijing 100043 P. R. China.

Abstract

In this study, a novel core@shell magnetic nanocomposite Fe₃O₄/CoFe-layered double hydroxide (Fe₃O₄@CoFe-LDH) was successfully synthesized by the co-precipitation method, and then employed as an efficient heterogeneous catalyst for activation of peroxymonosulfate (PMS) in removal of azo-dye acid orange 7 (AO7). The as-obtained nanocomposite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results from these characterizations showed Fe₃O₄@CoFe-LDH to possess good ferromagnetism and a perfect crystalline structure with a typical core@shell morphology. The system of Fe₃O₄@CoFe-LDH11/PMS (cobalt : iron molar ratio of 1 : 1) achieved 95.1% removal rate of AO7 (40 mg L^-1) within 15 min under the optimized conditions, which outperformed bare Fe₃O₄ and raw CoFe-LDH11. Meanwhile, Fe₃O₄@CoFe-LDH11 displayed good adaptability in a wide pH range from 4 to 9 and relatively low PMS activation energy (39.9 kJ mol^-1). The interference tests revealed HCO₃ ^- to possess the strongest restriction effect. Only 57.7% AO7 was removed when 10 mM HCO₃ ^- was introduced, which was ascribed to HCO₃ ^- not only serving as a radical scavenger, but also increasing the pH of the system. The radical quenching tests demonstrated SO₄˙^- as the dominant reactive species during the catalytic reaction. Based on X-ray photoelectron spectroscopy (XPS) analysis, the core structure of Fe₃O₄ served as an electron donor for accelerating the cycle of Co(ii)/Co(iii) at the active site of the LDH outer shell. Also, Fe₃O₄@CoFe-LDH exhibited outstanding stability and recyclability, and maintained high degradation efficiency of AO7 even after five cycles. In sum, the proposed magnetic Fe₃O₄@CoFe-LDH nanocomposite has great potential for remediation of wastewater contaminated with synthetic dyes.