St. Petersburg Mining University (St. Petersburg, Russia):
Kozyrev B. A., Postgraduate Student, kozirev-48@yandex.ru
Sizyakov V. M., Professor, Doctor of Engineering Sciences, kafmet@spmi.ru

Consumption of primary ore raw materials ceases to be the main area of industrial development. Processing of the accumulated large-tonnage waste, considered as secondary raw materials, is increasingly becoming the focus of attention. This is due to several reasons. Firstly, the amount of waste is constantly growing, covering extensive areas; secondly, high-grade ore resources are limited and are depleted annually; thirdly, the waste contains large amounts of valuable components that can and should be extracted. Red mud, alumina production waste, is one of such secondary raw materials. Its processing was first suggested back in the 19 century, when the technology for producing alumina from bauxite by the Bayer method was being developed, however no specific solution has been designed to date. The professional community have been working in this area for many years, numerous applications have been invented for red mud, and yet there is still no cost-effective technology for its processing. This article describes an integrated technology for the utilization of red mud, or rather for its heap leaching by the formate method to obtain commercial solutions for further processing into products and de-alkalized red mud with the mass fraction of Fe₂O₃ of at least 60 % to make it suitable for use as a raw material in the iron industry. Studies have confirmed the relevance of using heap leaching for red mud and the possibility of transferring valuable components (scandium, sodium, calcium, aluminum, rare earth metals) into the solution without any effect on iron. Preliminary cost and profit calculations have shown high economic efficiency of the technology.

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