Synthesis of Zinc Oxide Nanoparticles during the Processing of Galvanic Sludges

It was shown for the first time that zinc oxide nanoparticles can be synthesized by processing galvanic sludges by microemulsion leaching and subsequent precipitation of nanoparticles in this microemulsion. Model systems with ZnO and Zn(OH)₂ were used to study the leaching of zinc into reverse microemulsions in the sodium dodecyl sulfate–1-butanol–kerosene–water system containing di(2-ethylhexyl)phosphoric acid, caproic acid, or a mixture of tributyl phosphate and acetic acid as an extractant. The best leaching results were obtained for the microemulsion with di(2-ethylhexyl)phosphoric acid. Using a model system of zinc hydroxide contaminated with iron(III) hydroxide, it was shown that zinc can be selectively extracted into a microemulsion. A method for the synthesis of nanoparticles was developed, which comprised microemulsion leaching of zinc, separation of the unreacted solid phase, precipitation of ZnO nanoparticles from the microemulsion with an aqueous NaOH solution, separation of the precipitate, and washing and drying it. Using a model system with ZnO, this method produced spherical nanoparticles 34 ± 9 nm in diameter (according to transmission electron microscopy data); analysis of the X-ray powder diffraction pattern showed that ZnO was obtained.