Efficient degradation of Rhodamine B by magnetically recoverable Fe3O4-modified ternary CoFeCu-layered double hydroxides via activating peroxymonosulfate

Environment-friendly nano-catalysts capable of activating peroxymonosulfate (PMS) have received increasing attention recently. Nevertheless, traditional nano-catalysts are generally well dispersed and difficult to be separated from reaction system, so it is particularly im-portant to develop nano-catalysts with both good catalytic activity and excellent recycling efficiency. In this work, magnetically recoverable Fe3O4-modified ternary CoFeCu-layered double hydroxides (Fe3O4/CoFeCu-LDHs) was prepared by a simple co-precipitation method and initially applied to activate PMS for the degradation of Rhodamine B (RhB). X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), and vibrating sample magnetometer (VSM) were applied to characterize morphology, structure, specific surface area and magnetism. In addition, the effects of several key parameters were evaluated. The Fe3O4 /CoFeCu-LDHs exhibited high catalytic activity, and RhB degradation efficiency could reach 100% within 20 min by adding 0.2 g/L of catalyst and 1 mmol/L of PMS into 50 mg/L of RhB solution under a wide pH condition (3.0-7.0). Notably, the Fe3O4/CoFeCuLDHs showed good super-paramagnetism and excellent stability, which could be effectively and quickly recovered under magnetic condition, and the degradation efficiency after ten cycles could still maintain 98.95%. Both radicals quenching tests and electron spin resonance (ESR) identified both HO center dot and SO 4(center dot-) were involved and SO4 center dot- played a dominant role on the RhB degradation. Finally, the chemical states of the sample's surface elements were mea-sured by X-ray photoelectron spectroscopy (XPS), and the possible activation mechanism in Fe3O4 /CoFeCu-LDHs/PMS system was proposed according to comprehensive analysis. (c) 2021 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

Environment-friendly nano-catalysts capable of activating peroxymonosulfate have been attracting increasing attention. Fe3O4-modified ternary CoFeCu-layered double hydroxides exhibited high catalytic activity for Rhodamine B degradation, with the catalyst showing good super-paramagnetism, stability, and recyclability. The activation mechanism involved HO center dot and SO4(center dot-) radicals, with SO4(center dot-) playing a dominant role in RhB degradation.