Surface nanostructuration of ZnO and ZnO:Cd sub-microstructures and their use as suspended and immobilized photocatalysts for rapid degradation of methylene blue

Abstract

ZnO and ZnO:Cd (Cd = 2%) powders were fabricated by hydrothermal synthesis followed by a calcination step, and then studied as photocatalysts for degradation of methylene blue (MB) in water. Powders were analyzed by electron microscopy, and Raman and photoluminescence spectroscopies. After the calcination step at 300 °C for 1.5 h, ZnO and ZnO:Cd photocatalysts with conveniently nanostructured surfaces were achieved. The nanophotocatalysts were then tested for MB degradation using two methods: a) suspended powders in MB solutions and b) immobilized powders on glass substrates. The suspended powder method showed excellent efficiency for the removal of MB, reaching values close to 99% in less than 60 min for the Cd-doped samples. The immobilized powder method showed less efficiency (up to ∼75% removal after 200 min for the Cd-doped sample), however it allowed easy recovery of the photocatalysts after the degradation process.