Enhanced activation of persulfate by magnetic CuFe-layered double hydroxide nanocomposites under visible light irradiation for degradation of quinoline

Magnetic CuFe-layered double hydroxide (Fe3O4@CuFe-LDH) nanocomposites were prepared with different Cu/Fe molar ratios for boosting the persulfate (Ps) activation under visible light irradiation. The LDH products were characterized in different ways. Recalcitrant quinoline (Qu) was the target pollutant in the experiments. It was found that the presence of the LDH photocatalyst caused significant enhancement in the Qu degradation so that the Vis/Ps/Fe3O4@LDH process could give 92.1% degradation and 70.5% mineralization efficiencies after 30 min operations at room temperature. The appropriate optimum conditions were Ps concentration of 450 mg/L, catalyst dosage of only 35 mg/L and the Cu/Fe molar ratio in the LDH structure of 3:1. The solution natural pH of about 6 provided the best performance. The LDH photocatalyst regeneration, in five cycles, each after a simple elution, exhibited good stability and reusability with an overall decrease of 4.9% in the activity. The presence of some co-existing anions of aqueous solutions causes diminishing the process efficiency. A pathway of Qu mineralization was proposed based on the identified intermediates. Taking into account the electrical energy and the consumed materials, an operating cost of $31.6/m(3) was estimated for one order of magnitude reduction in the pollutant concentration.