ECONOMIC EFFICIENCY OF EXTRACTING IRON AND PRECIOUS METALS FROM PYRITE CINDER

Abstract

Pyrite cinders are high-tonnage waste from sulfuric acid production, accumulated in the amount of tens of millions of tons only in Russia and the post-Soviet countries. These wastes contain up to 40–63% iron, as well as non-ferrous (Cu, Zn, Co) and precious metals (Au up to 10–20 g/t, Ag up to 20–70 g/t). This paper presents a comprehensive analysis of pyrite cinder processing technologies and assessment of their economic efficiency. Three main technological directions are considered: hydrometallurgical (acid leaching), pyrometallurgical (chlorinating firing) and combined (reducing firing - magnetic separation). It is shown that the most promising technologies are complex processing, which can extract up to 97% of iron, 76–82% of copper, and 71–99% of cobalt while simultaneously producing marketable products such as iron oxide pigments, precious metal concentrates, or precursors for lithium-iron-phosphate battery cathode materials. Economic calculations show that when processing 100 thousand tons of cinder per year using FePO₄ synthesis technology, a gross profit of up to 173 million USD/year is possible with a payback period of less than 4 months (excluding R&D and marketing costs). The chlorinating firing technology provides more modest but stable indicators (gross profit of USD 6.3 million/year, payback of 4.8 years). The main barriers to industrial implementation are the lack of regulatory incentives for processing man-made waste, insufficient technology development on an industrial scale, and logistical constraints. It has been established that the complex processing of pyrite cinders is not only ecologically necessary, but also economically highly profitable.