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We have carried out the laboratory study of the properties of zinc-containing sludge obtained after the recycling of waste from viscose fiber production via the calcium hydroxide method. A waste-free process of complex recycling of such sludge was developed. Based on this method, we developed the design and construction of a semi-industrial sludge processing located in the sludge storage facilities of "Cherkasy Khimvolokno" chemical plant. A scheme of complex processing of zinc sludge produced by "Cherkasy Khimvolokno" was offered. To completely remove organic compounds, the initial sludge was calcined in a muffle furnace at the temperature of 9000С for 1 hour. The recycling scheme was based on the treatment of roasted sludge with concentrated nitric acid. With this treatment, all soluble calcium, as well as iron and zinc, were transferred to the solution. The residual precipitate, which was insoluble in nitric acid and consisted mainly of calcium sulfate, was filtered off. The formed filtrate was alkalized to pH 4.2 to separate iron from zinc in the form of Fe(OH)3. Control of products at each stage of the process was carried out by X-ray fluorescence spectroscopy, X-ray diffraction, and chemical methods. Conditions of each stage in the laboratory process were specified. We proved the impossibility of waste-free sludge processing without roasting of its organic constituents. It was shown that the final products of such processing were the following: the powder for salt-affected soils reclamation, gypsum, ferric oxide, zinc oxide, metallic zinc, chemically precipitated chalk, and sodium nitrate.
Shaforost et al. (Thu,) studied this question.
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