CuMgAl-layered double hydroxide activating peroxydisulfate for efficient degradation of norfloxacin in sludge anaerobic digestion liquor

Abstract

Norfloxacin (NOFX) in the sludge anaerobic digestion liquor (ADL) should be removed before returning to the mainstream wastewater biological treatment system. In this study, CuMgAl-layered double hydroxide (LDH) activating peroxydisulfate (PDS) for NOFX degradation was conducted. Research results indicated that reaction temperature, CuMgAl-LDH dosage and inorganic anions content in the wastewater all showed significant influences on NOFX degradation. Mechanisms analysis confirmed that Cu(I)-Cu(II) redox cycle led to PDS activation, and SO4−, OH as well as 1O2 made primary contribution to NOFX degradation. CuMgAl-LDH stability and reusability as well as possible degradation pathway of NOFX were systematically investigated. In view of ADL characteristic, the optimal condition for NOFX degradation was determined as initial pH of 7, 35 °C, 0.5 g/L CuMgAl-LDH, 0.5 mmol/L PDS and removing carbonate and phosphate from ADL, which could achieve 67 % of degradation rate within 10 h. What's more, the ecotoxicity of NOFX and its main degradation products was assessed by ECOSAR prediction. This study provided primary guideline of copper-based LDH/PDS system for antibiotics removal in real wastewater matrixes.