Fabrication of NiO/Mg-Al layered double hydroxide with superior performance for peroxydisulfate activation

Mg-Al Layered double hydroxides (LDH) with weak alkalinity can improve the activity and stability of transitional metal oxides for peroxydisulfate (PDS) activation. Herein, NiO supported on LDH (Ni-LDH-TP) and Ni doped LDH samples (Ni-LDH-CP and Ni-LDH-SP) were prepared by two-step precipitation and co-precipitation methods, respectively. Their structure and surface properties were characterized and their performance for PDS activation was compared using ciprofloxacin as the target pollutant. The results indicate that Ni-LDH-TP exhibited much higher activity than Ni-LDH-CP and Ni-LDH-SP due to its more surface exposed NiO. The two-step precipitation method should be a better alternative for the synthesis of Ni-LDH catalyst for PDS activation. Ni-LDH-TP exhibited high activity over a wide pH range and good reusability in the presence of bicarbonate, demonstrating its potential application in real water treatment. Activated PDS and SO4 center dot- should be the dominant reactive species for ciprofloxacin degradation. This finding provides an effective strategy for preparing Ni-based PDS catalyst.