Synergistic effect between adsorption and Fenton-like degradation on CoNiFe-LDH/ZIF-8 composite for efficient degradation of doxycycline

This study aimed to remove doxycycline (DC) from wastewater via a synergistic effect between adsorption and Fenton-like degradation processes. For this purpose, cobalt-nickel-iron-layered double hydroxide/zeolitic imidazolate framework-8 (CoNiFe-LDH/ZIF-8) was designed to have a continuous redox cycle between the transition metals of CoNiFe-LDH. Furthermore, a high adsorption capacity is provided mainly by ZIF-8, which also endows electrons to the reduced metals of LDH via zinc-oxygen-metal (Zn-O-M) bonds. The morphology, chemical structure, surface charge, and crystallinity of CoNiFe-LDH/ZIF-8 were investigated. The adsorption percentage of DC onto CoNiFe-LDH/ZIF-8 was estimated to be 45.62 %, while the degradation percentage reached 98.5 % after 90 min. The removal mechanism was proposed based on the experimental results, Zeta Potential, and X-ray photoelectron spectroscopy (XPS) analyses. In addition, Liquid Chromatography-Mass Spectrometry predicted the degradation pathways and the formed byproducts. Based on the promising reusability of CoNiFe-LDH/ZIF-8, it could be applied in industrial applications.