Sequential lixivation and precipitation of metals from refractory ores by utilising variable oxidation reduction potentials and a variable PH system

Abstract

This invention relates to an improved electrochemical process for winning platinum group and incidental precious metals from ore. The process utilizes a peroxide leach in combination with electricity to produce higher valency metals and comprises the following steps: combining ground ore with a solution comprising water with a selected amount of H2O2 and an anion source to form a slurry; applying a direct current while allowing the metal in the ore to leach into the solution for a selected period of time; filtering and clarifying the leached slurry to obtain a pregnant solution; and treating the pregnant solution to yield metal, metal salts or both.

Description

FIELD OF THE INVENTION[0001]The invention relates generally to a method of separating metals from another material, and in particular, to a method for extracting platinoids, rare earths, and transition metals from disseminated and difficult matrixes by utilizing controlled parameters of a solution.BACKGROUND OF THE INVENTION[0002]Known processes for the commercial extraction of precious metals from ores at present consist mainly of two main operations: concentration and then refining. Concentration is the separation of a metal or a metallic compound from gangue of the ore. Refining is the production of a metal into a pure or nearly pure state suitable for use. Concentration and refining processes can be mechanical, chemical, or electrical and any, combination thereof. Mechanical separation techniques include gravity separation and floatation. Chemical separation techniques include smelting, amalgamation and cyanidation. Electrical separation techniques include electrolysis.[0003]Man...

AI Technical Summary

Benefits of technology

[0006]It is the object of the invention to make refractory ores such as slates, mudstones, shales, serpentines and other rocks which very easily become slimes when ground, very much easier to process and filter.

[0008]In particular, it is the object of the invention to provide a method of separating metals from another material wherein said method requires a relatively low equipment infrastructure investment, is relatively simple to operate, and is quick and environmentally benign while having a relatively high throughput.

[0009]The invention achieves most of these objectives and relates to an improved method of varying the ph electrically and the oxidation-reduction potential of the solution as well as controlling the viscosity of the solution. The variable control of the oxidation-reduction potential makes it possible to maximize or minimize the extraction of any particular metal.

[0010]The process also allows the oxidation-reduction potential to be pushed up to new heights such that metals such as platinum, scandium, and other metals which are difficult to take into solution are now much more easily solubalized. The process utilizes a peroxide leach in conjunction with suitable anion and a variable direct (DC) current to produce a variable high oxidation-reduction potential which, by adding more energy to the solution in the form of ultra violet light, ultra sonic energy, or more reagents and electric power, can be pushed far beyond normal and can consequently livivate or leach very refractory metals in extremely difficult matrixes. The process utilizes a ground up ore slurry with a hydrogen peroxide (H2O2) leach in conjunction with a variable DC current and variable amounts of energy such as ultraviolet radiation or ultrasound until a desired oxidation-potential is reached and then the reaction is allowed to proceed until the oxidation-reduction meter indicates that the metals, after a selected period of time, have been dissolved, at which time the slurry is filtered and clarified to give a pregnant solution The pregnant solution is then treated, either electrically or chemically, to yield the metal or metal salts or both.

[0013]The method can be directed at recovering the PGM (or any group that have similar chemical characteristics to one another such as the rare earths, the neuclides, or the transition metals), in which case the method can first be applied using hydrochloric acid (HCl) as the anion source with the oxidation-reduction potential suitable for platinum and treating the pregnant solution using techniques that are known to the art. The method can then be applied again to the remaining ore using sulfuric acid (H2SO4) as the anion source and then treating the pregnant solution to recover palladium from the solution using techniques that are known to the art. This process can, in many cases, give a much cleaner division of the individual metals.

Problems solved by technology

Because of the complexity of most of these ores and the difficulty of concentrating them, these deposits are not utilized.

Such concentration is energy intensive, incurs significant losses, and requires high capital investment for equipment infrastr.

Also, known processes for processing concentrate require numerous complex and time consuming steps, some of which are not environmentally friendly.

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