Rio Tinto has filed a patent for a method of processing a pyrite-containing slurry. The method involves removing pyrite from the slurry and forming an inert stream and a pyrite-containing material. The slurry includes tailings from a tailings dam or an ore processing plant. The method also includes leaching a metal sulfide-containing material and the pyrite-containing material with a leach liquor and microbes. The pyrite in the material generates acid and heat that facilitate leaching metal from the metal sulfide-containing material, while the microbes oxidize ferrous iron to ferric iron. GlobalData’s report on Rio Tinto gives a 360-degree view of the company including its patenting strategy. Buy the report here.

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According to GlobalData’s company profile on Rio Tinto, Zinc recovery was a key innovation area identified from patents. Rio Tinto's grant share as of September 2023 was 55%. Grant share is based on the ratio of number of grants to total number of patents.

Method of processing pyrite-containing slurry and leaching metal sulfide-containing material

Source: United States Patent and Trademark Office (USPTO). Credit: Rio Tinto

A recently filed patent (Publication Number: US20230295768A1) describes a method for processing a pyrite-containing slurry. The method involves removing pyrite from the slurry, resulting in an inert stream and a pyrite-containing material. The pyrite-containing material is then leached with a leach liquor and microbes to extract a metal from a metal sulfide-containing material. The pyrite in the material generates acid and heat, which aids in the leaching process, while the microbes oxidize ferrous iron to ferric iron.

The patent claims also describe additional steps and configurations for the method. These include floating the pyrite-containing material in the slurry to separate it into the inert stream and the pyrite-containing material. Before flotation, a size separation step can be performed to separate larger particles in the pyrite-containing material. The method also includes reducing the size of the larger particles in a size reduction circuit and returning them to the size separation step. The operating conditions can be selected to ensure that the pyrite particles in the remaining slurry have the required particle size distribution for the downstream leach step.

The patent further mentions the use of the inert stream as a source of water in processing plants for recovering metal from the metal sulfide-containing material. The metal in this case is specified as copper, and the metal sulfide-containing material is a copper sulfide mineral. The pyrite is stated to be 1-10 wt. % of the total mass of the copper sulfide-containing material and the pyrite-containing material.

The patent also describes a heap leaching method for a mined material that contains a metal sulfide-containing material. This method involves leaching a heap of agglomerates produced from a pyrite-containing material and the mined material with a leach liquor and microbes. The pyrite in the pyrite-containing material generates acid and heat, facilitating the leaching process, while the microbes oxidize ferrous iron to ferric iron. A pregnant leach liquor containing the metal in solution is collected from the heap.

Additionally, the patent mentions a flotation circuit for an ore processing plant. This circuit includes a mill feed flotation circuit and a pyrite flotation circuit. The pyrite flotation circuit is configured to process the pyrite concentrate stream, which is the pyrite-containing slurry. The method described in the patent can be applied in this circuit to remove pyrite and leach a metal sulfide-containing material.

Overall, the patent presents a method for processing pyrite-containing slurry and extracting metal from metal sulfide-containing materials using leaching and microbial oxidation. The method includes various steps and configurations to optimize the process and can be applied in flotation circuits and heap leaching methods.

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GlobalData, the leading provider of industry intelligence, provided the underlying data, research, and analysis used to produce this article.

GlobalData Patent Analytics tracks bibliographic data, legal events data, point in time patent ownerships, and backward and forward citations from global patenting offices. Textual analysis and official patent classifications are used to group patents into key thematic areas and link them to specific companies