CeO2@LDH decorated 3D porous module with mortise-tenon structure: Activation of peroxymonosulfate for ultrafast removal of tetracycline

Abstract

Constructing a robust catalytic module with lower energy consumption, fast liquid transport, and simultaneous highly catalytic oxidizability presents an enticing alternative for industrialized water treatment. Herein, a kind of cerium oxide (CeO2) loaded layered double hydroxide (LDH) composites that was fabricated by seeds embedded epitaxial growth based on hydrothermal method anchored on a three-dimensional porous polyvinylidene fluoride (PVDF) framework (denoted as CeO2@LDH-PVDF) and function as an efficient catalytic activator for peroxymonosulfate (PMS) activation. This module features as lamellar LDH nano-flowers not only in situ anchoring onto both sides of the PVDF surface but also along the wall of the pores in an ab-plane vertically interlaced growth pattern. A packed tower device suitable for the catalytic module is also proposed as proof of concept for consecutive pollutants disposal. This module exhibits dual functions of filtration and oxidation, demonstrating a promising removal efficiency for tetracycline (95.8%, 30 mg/L) in conjunction with PMS. Accurate operation parameters are obtained by using the response surface methodology to further reduce the energy consumption (CeO2 containing: 9.03%, PMS concentration: 0.798 mM; pH: 6.513). Encouragingly, the CeO2@LDH-PVDF is not only capable of achieving ultrafast removal in flowing various contaminants, but also reveals wide practical applicability in tap water and reservoir. Moreover, it provides evidence that the binding force between LDH and PVDF is enhanced by virtue of the unique “Mortise-Tenon” structure, which is conducive to maintaining the catalytic activity. Furthermore, the formation of a complex of M−(HO)OSO3− and the succeeding redox cycle of Ni2+/Ni3+, Fe2+/Fe3+, Co2+/Co3+ explain the generation of reactive radicals in PMS activation. Moreover, a new redox cycle of Ce3+/Ce4+ promotes the utilization efficiency of PMS. Three possible tetracycline degradation pathways are proposed and the toxicity of the by-products is reduced. Finally, the module possesses an ideal universality, good cycling stability, favorable antifouling performance, and superior renewability. It is predicted to be integrated with multiple mature technologies to conduct industrial water treatment due to its changeable shape and durability.