Dysprosium doped double layered hydroxide as an efficient catalyst for photooxidation of pharmaceutical pollutants

Abstract

In this work, layered double hydroxides (LDHs) containing 1, 2, and 5% Dy were successfully prepared by the precipitation method. The partial substitution of Zn by Dy cations resulted in highly crystalline LDH structures, as a single crystalline phase, with a predominant 3R1 stacking favored by the intercalation of carbonate anions. The ZnAlDy-LDHs were calcined at 500 °C and produced a mixed metal oxides (MMOs), mainly ZnO and amorphous Al species. The catalytic activity of the ZnAlDy-MMOs was evaluated in the photodegradation of the antibiotic sulfamethoxazole (SMX) as pharmaceutical pollutant model. The ZnAlDy-MMO containing 2% Dy exhibited the best catalytic activity with 98% of degradation efficiency under UV light irradiation after 90 min. The catalyst reusability and stability study revealed that the ZnAlDy-MMO was restored to the LDH structure as a result of the structural memory effect triggered by hydration. According to our results, 98% of SMX was degraded by the ZnAlDy-LDH containing 2% Dy within 45 min of irradiation; this degradation efficiency was higher than that achieved by commercial ZnO and P-25 TiO2 photocatalysts (∼85%). Therefore, ZnAlDy2-LDH is a promising eco-friendly catalyst for the photodegradation of pharmaceutical pollutants since its synthesis is simple and does not require a calcination treatment to promote an improved catalytic response.