Peroxydisulfate intercalated Ni-Zn-Al layered double hydroxide for ciprofloxacin degradation: The synergistic effect of the radical pathway and the non-radical pathway

Although several strategies were developed to activate peroxydisulfate (PDS) through layered double hydroxides (LDHs) for the degradation of organic contaminants, effectively utilizing the structure of LDHs to improve active sites and electron transfer efficiency remained a challenge. The research prepared Ni-Zn-Al LDH-0.1-PDS composite materials through ion exchange. After the PDS intercalated, the efficiency of degradation was significantly improved. The material showed optimal performance at Ni/Zn = 0.1, under the conditions of 1 g/L dosage and 10 mg/L ciprofloxacin (CIP), the degradation rate reached 89.86 % within 120 min. The quenching experiment demonstrated that the reaction was dominated by non-radical pathways represented by e − (80.53 %), h + (70.47 %), and 1 O 2 (58.70 %) and assisted by free radicals denoted as O 2 − (27.84 %). The DFT calculation revealed that the O O bond length increases while the bond energy diminishes upon the incorporation of S 2 O 8 2− into the LDH interlayer, illustrating that PDS existed in a metastable state within the LDH interlayer, where the O O bond exhibited heightened reactivity, facilitating electron acquisition and subsequent cleavage due to the interlayer confinement effect of LDH on anions. This research offered novel insights on altering the composition and structure of LDHs to promote non-radical activation of PDS.