When aluminum is obtained by electrolysis of cryolite-alumina melts when the baths are sent for capital repairs, a solid technogenic product is formed – waste lining of electrolytic cells (WLEC). The volume of formation of WLEC is 30-50 kg per 1 ton of aluminum. Currently, it is mainly stored at landfills near industrial enterprises, causing harm to the environment. However, this technogenic raw material contains valuable components (fluorine, aluminum, sodium) that can be extracted to produce fluoride salts, which are in demand during the electrolytic production of aluminum. The objects of research were samples of the coal part of the waste lining of dismantled S-8BM (E) type electrolytic cells of «RUSAL Krasnoyarsk» JSC (Krasnoyarsk) of RUSAL company. According to the X-ray experiment diffraction analysis (using a Bruker D8 ADVANCE diffractometer) of the phase composition of the samples, it was found that the main fluorine-containing compounds are cryolite, chiolite, sodium and calcium fluorides. The total fluorine content in the studied samples averaged 13.1 %. We conducted studies on the leaching of fluorine from WLEC with a solution of caustic alkali (NaOH concentration – 17.5 g/dm 3 ). The process was carried out in a mechanically agitated reactor using a BIOSAN MM-1000 top drive laboratory stirrer with a two-blade nozzle. By the method of mathematical planning of a three-factor experiment, the mutual influence of three leaching conditions on the optimization parameter was established – the extraction of fluorine in solution (in percent). The maximum recovery of fluorine from WLEC to the leach solution averaged 86.4 % and was achieved with the following indicators: process temperature –95 ° C, the ratio of liquid to solid phase– 9:1, duration – 210 min.
With the depletion of rich gold-bearing ores, the processing started to use polymetallic ores, which, in addition to precious metals, contain other elements that could be valuable after recovery. The problem of using such ores is extremely difficult because of the high cost of recovery of associated valuable components. The paper presents the results of studies on the integrated use of extracted gold-bearing raw materials based on the example of the Berezitovoye deposit (Amurskaya oblast), they have low content of precious metals and many heavy non-ferrous metals (copper, lead). Experimental work was carried out to obtain copper by the method of cementation from solutions formed after the leaching of the impurities of gold-containing cathode deposits with hydrochloric acid. The cementing metal was iron turnings (waste products of the turning shop of the enterprise). Next, it was proposed to use cemented copper as a collector during re-melting of slags – wastes of processing of low-grade polymetallic ores containing precious metals. The authors obtained ingots of alloyed gold with gold weight fraction of 16 %, which meets the requirements of TU 117-2-7-75 on the content of non-ferrous metals. During hydrochloric acid treatment of cathodic deposits silver partially passed into the solution, it was recovered together with cemented copper and, in subsequent melting, passed into alloyed gold. Thus, the method proposed by the authors helps to reduce the content of precious metals in the «incomplete production cycle» of the gold recovery factory. The opportunity of selling the cementation copper at the enterprises specializing on manufacturing of jewels is shown; the expected economic effect at the same time amounted to more than 1.8 million rubles.
