In situ synthesis of NiFe-LDH/chitosan composite aerogel beads for photo-assisted activation of PMS in water purification.

The increasing prevalence of antibiotics in aquatic environments has emerged as a pressing global environmental concern. In this paper, aerogel beads of chitosan (CS)/nickel iron layered double hydroxide (NiFe-LDH) were fabricated via an in-situ one-step synthesis strategy, wherein NiFe-LDH was synchronously formed during the alkaline crosslinking of CS. This in-situ fabrication approach not only reduces the consumption of alkaline reagents but also enables the uniform dispersion of NiFe-LDH within the bead matrix. The composite sample CS/NiFe20 exhibited excellent degradation performance for the photo-assisted peroxymonosulfate (PMS) activation during the degradation process of oxytetracycline (OTC) with a removal efficiency of 94.99% for OTC. The reaction rate constant k of CS/NiFe20 was 0.1012 min-1, which was 4.77 times and 5.30 times higher than those of the CS/NiFe20/PMS and CS/NiFe20/photo systems, respectively. Notably, CS/NiFe20 maintained prominent catalytic activity under broad pH ranges (pH=3-11), coexisting inorganic anions, and complex real-water matrix conditions, demonstrating strong anti-interference capability for practical application. The CS/NiFe20 in PMS/photo system achieved synergistic OTC degradation dominated by non-radical pathways with auxiliary radical pathways. Intermediate products were identified via liquid chromatography-mass spectrometry (LC-MS), and density functional theory (DFT) calculations clarified the reaction mechanism. Toxicity evaluation using T.E.S.T. software confirmed a marked reduction in the toxicity of degradation intermediates. The aerogel beads exhibited superior recyclability and suppressed metal ion leaching during oxidation. This study provides a facile and innovative route to fabricate high-performance recyclable bead-shaped catalysts, and offers promising insights for practical environmental remediation.