Rare and rare-earth elements of technogenic wastes of thermal energy enterprises of Primorsky Krai, Russian Federation and methods for their effective extraction

摘要

Rare and rare-earth metals are strategic resources that play a key role in the computer, mobile, medical, fuel and energy, automotive and many other industries. Studies of the composition of ash and slag waste from thermal power enterprises are widely represented in the works of both foreign and Russian researchers. The content of rare and rare-earth metals varies depending on the properties of the original solid fuel and the method of its combustion, yet in general it is noted that most of them are present in thennal energy waste in high concentration that is sufficient for industrial processing. At the same time, despite the significantly lower production cost (by 50-60%) due to the compositional peculiarities of ash and slag waste that contains much more mineral forms than conventional ores, the processing of such fonns requires more complex technological solutions. The team of authors of this scientific work conducted research to assess the content of rare and rare earth elements in industrial waste from thermal energy enterprises of Primorsky Krai, Russian Federation. The object of the study were ash and slag waste from the CHPP of Primorskaya TPP and CHPP-2, Vladivostok. Due to enrichment process (flotation, magnetic separation), two fractions were separated from the waste: a non-magnetic light fraction and a non-magnetic heavy one. As the analysis showed (inductively coupled plasma mass spectrometry), the following rare and rare-earth elements (light / heavy fractions, g / t) prevail in ash and slag waste, in decreasing order of content: lanthanum (29.3 / 60.2); cerium (57.4 / 116.5); praseodymium (5.3 / 11.8); neodymium (23.5 / 50.7); samarium (5.0 / 9.5); gadolinium (4.6 / 9.7); dysprosium (4.4 / 8.5); erbium (2.8 / 5.4); ytterbium (2.8 / 6.0). Holmium, terbium, europium, lutetium and thulium are present. It should be noted that the studied rare and rare-earth elements are mainly concentrated in the heavy non-magnetic fraction, and therefore, are more associated with mineral components than with the light fraction, which is mainly represented by organic components. In addition to studying the composition of thennal energy wastes for the presence of rare and rare-earth elements, the authors of the work substantiated the theoretical mechanism of their mechanochemical activation with the directed fonnation of the necessary changes in the physicochemical properties of minerals and their associates to intensify the processes of metal extraction.