ZnAl/ZnSn(OH) composite photocatalyst for emerging contaminants degradation in water

Layered double hydroxides (LDH) are a versatile group of lamellar inorganic solids with a brucite-like structure similar to hydrotalcite that has undergone multiple improvements to be applied in various fields such as carbon dioxide sequestration, catalysis, drug delivery, energy conversion, and storage, as well as environmental remediation. It is then that this material becomes interesting for its application in water treatment since it has various practical features, e.g. tunable structure, excellent thermal stability, memory effect, high specific surface, high dispersion and regenerative viability. By taking advantage of this versatility, in this research work, the synthesis and characterization of ZnAl hydrotalcite modified with Sn through the coprecipitation method is reported. The presence of hydrotalcite ZnAl, and Zinc hydroxystannate phases were observed in the X-ray diffraction spectra. In the same way, it was possible to observe through the SEM micrographs the morphology associated with the union of both phases; i.e. lamellar and microcubic. In the bandgap energy measurement, the shift of the hydrotalcite value is observed as well as the appearance of another signal of zinc hydroxystannate species. The obtained materials were evaluated for the photocatalytic degradation of acetaminophen to 20 ppm under UV light. ZnAl/ZnSn(OH)6 composite showed better efficiency in the paracetamol degradation under UV light. Additionally, studies of the variation of ZnAl/ZnSn(OH)6 ratio and pH values of the solution were carried out, achieving photodegradation efficiency > 95 %, after 60 min of irradiation, using 0.15 g of ZnAl/ZnSn(OH)6 photocatalyst at pH= 6. The reusability was evaluated by testing the material in photodegradation cycles.