Efficient degradation of wastewater by ultra-low platinum doped ZnO lamellar nanoflowers via photoinduced formation of hydroxyl radicals

Photocatalytic degradation technology is a promising strategy for the water treatment, which has many advantages such as saving time, cleanliness and environmental friendliness. In this study, ultra-low amount (0.01wt.%) of nano platinum (Pt) obtained from one-pot reduction method, was doped onto zinc oxide (ZnO) to form a lamellar nanoflower (Pt-ZnO). The characterization of Pt-ZnO was put forwards via scanning electron microscopy, high-angle annular dark-field scanning transmission election microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, liquid chromatography-mass spectrometry, etc. The highest degradation efficiencies of methylene blue (MB), rhodamine B (Rh B), methylene orange (MO), and acid black ATT (ATT) after being treated by Pt-ZnO for about 60min reached 99.9%, 99.9%, 96.0%, and 97.8% respectively. While the MB and Rh B remained at a degradation efficiency of 99.9% even after being reused 5 times. Surprisingly, Pt-ZnO showed the removal rate of industrial effluent containing acid dyes was 93.9% and the chemical oxygen demand (COD) of wastewater was significantly reduced. Experimental results of LC-MS and free radical scavenging testing indicated MB was mainly split through the continuous open-ring cleavage of C-N bond in N, N-dimethylamine group by ·OH, and finally decomposed into H2O and CO2 achieving the decolorization.