Recovery of Zn from wastewater of zinc plating industry by precipitation of doped ZnO nanoparticles
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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.
KeywordsAvoidance of hydroxides Nanosized precipitates Wastewater treatment Zincite
The authors thank Alexander Reul for his assistance in the lap and for performing the Raman measurement. Furthermore, the authors wish to thank Nikolai Petersen for his helpful advices regarding magnetic measurements and the corresponding data interpretation. The Mineralogical State Collection Munich is acknowledged for providing the Raman instrument. This study was supported by the Bavarian State Ministry of the Environment and Consumer Protection (StMUV) within the frame of ForCycle (#BAFO1SoFo-65214).
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