Hierarchical porous N-doped carbon encapsulated CoFe2O4-CoO nanoparticles derived from layered double hydroxide/chitosan biocomposite for the enhanced degradation of tetracycline

Abstract

Developing a sustainable, efficient, and cost-effective heterogeneous catalyst for advanced oxidation processes is challenging in wastewater remediation. Herein, chitosan intercalated CoFe-layered double hydroxide was first employed as a precursor to fabricate a novel CoFe2O4-CoO/N-doped carbon composite (CoFe-LDO/NC) via a simple “in-situ coprecipitation-calcination” method. The resulting CoFe-LDO/NC was carefully characterized and employed to degrade tetracycline (TC) with the assistance of peroxymonosulfate (PMS). Under the optimum conditions (30 mg L−1 TC, 0.4 g L−1 catalyst, 0.4 g L−1 PMS, pH = 5), the degradation efficiency and mineralization degree reached 97.6% and 60.7% within 30 min, respectively. The superior activity of CoFe-LDO/NC was ascribed to its well-dispersed metal nanoparticles, large specific surface area (230.7 m2 g−1), hierarchical porous structure, and intensified electron transfer efficiency. The quenching test revealed that both the sulfate radicals and singlet oxygen were the dominant active species in the system. The degradation mechanism and TC evolution route were speculated by X-ray photoelectron spectroscopy and liquid chromatography-mass spectrometry. Escherichia coli growth inhibition test exhibited remarkable detoxification of TC solution after degradation. Moreover, CoFe-LDO/NC could be easily collected by magnetism, and 94.3% of its original activity was retained after five cycles. This work offers a green and scalable approach for the rational design of heterogeneous Co-based catalysts for degradation.