Synergetic Removal of Pb(II)- and Sulfonamide-Mixed Pollutants using Ni/Co Layered Double Hydroxide Nanocages Coupled with Peroxymonosulfate

Abstract

Organic pollutants are often present in wastewater coupled with toxic metallic ions, which are harmful to both human beings and the ecological environment, and their simultaneous removal is of great significance. In this work, hollow Ni/Co layered double hydroxide (LDH) nanocages were synthesized through the hydrothermal method by using zeolitic imidazolate framework-67 as a self-sacrificial template, and it was further used as a catalyst to activate peroxymonosulfate (PMS) for sulfonamide (SA) degradation and an adsorbent for Pb(II) removal simultaneously. The materials were characterized using various techniques, and the effect of parameters including the dosage of the catalyst and PMS, initial temperature, and pH on the performances of the LDH nanocage was investigated. Nearly 80% of SA (15 mg/L) could be degraded via PMS activation, whereas ∼93% of Pb(II) (20 mg/L) could be removed simultaneously within 60 min. During the reaction, there were redox cycles for both Co and Ni over the surface of LDH, but Pb did not participate in the process, and it had a slightly negative effect on SA degradation. The quenching experiments and the electron paramagnetic resonance results showed that the radicals (•OH, •SO4–, O2•–, and 1O2) generated from PMS activation participated in the process. Finally, the possible mechanism and degradation pathways were proposed, based on the intermediate products identified, and the toxicity of the intermediate products was evaluated.