Oxidation of Zinc Microparticles by Microwave Plasma to Form Effective Solar-Sensitive Photocatalysts

The presented work studies the processes of synthesis of ZnO microstructures using atmospheric-pressure microwave nitrogen plasma and investigates their photocatalytic activity in the processes of degradation of 2,4-dinitrophenol and the antibiotic ciprofloxacin when irradiated with sunlight. The work proposes an effective method for formation of photosensitive ZnO powders. Due to the features of plasma treatment in the open atmosphere of zinc metal microparticles, ZnO structures are formed with sizes from hundreds of nanometers to several micrometers with various micromorphologies. The lattice parameters of ZnO structures are characteristic of a hexagonal unit with a = 3.258 angstrom and c = 5.21 angstrom, volume 47.95 angstrom 3. The size of the crystallites is 48 nm. The plasma treatment was performed by means of a 2.45-GHz plasmatron at a power input of 1 kW in nitrogen flow at a rate of 1-10 L/min. Zn microparticles were injected into the microwave plasma at a mass rate of 20 g/min. High photoactivity was demonstrated (rate constants 0.036 min-1 and 0.051 min-1) of synthesized ZnO structures during photo-degradation of 2,4-dinitrophenol and ciprofloxacin, respectively, when exposed to solar radiation. Photo-active structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds. Structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds, and also in scintillation detectors, phosphors.