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Recovery of Zn from wastewater of zinc plating industry by precipitation of doped ZnO nanoparticles

John, M., Heuss-Aßbichler, S., Ullrich, A.
International journal of environmental science and technology 2016 v.13 no.9 pp. 2127-2134
Raman spectroscopy, X-ray diffraction, alkalinization, chemical precipitation, chromium, copper, electron microscopy, industry, iron, nanoparticles, nickel, pH, sodium hydroxide, temperature, wastewater, wastewater treatment, water purification, zinc, zinc oxide
In this study, a facile precipitation process to treat wastewater from zinc plating industry is presented. Water purification rates of Zn range between 96.40 % and 99.99 % depending on the reaction conditions. Optimal results are gained at a low pH value of 9, low temperature of 40 °C and a fast alkalization using NaOH solution containing 16 % pure NaOH. Traces of Ni, Fe, Zn, Cu and Cr present in the wastewater were almost completely removed. The precipitates were analysed by X-ray diffraction, infrared and Raman spectroscopy, electron microscopy and magnetic measurements. They consist of doped ZnO as a main phase. Although ZnO exclusively crystallizes in nanoparticle size, the morphology is directly influenced by the experimental parameters. Additionally, very small amounts of ZnCO₃ and Zn(OH)₂ were detected. Magnetic investigations indicate the incorporation of Ni and Fe into the ZnO lattice. The measured saturation magnetization is ~0.01 emu/g and the Curie temperature is ~75 °C.