Precious Metal Recovery via Pressure Oxidative and Halide Leaching
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Solution Overview
Problem
Existing methods for separating precious metals from mineral-based starting materials are inefficient and economically unviable, often requiring harsh conditions and expensive reagents, particularly due to the need for roasting steps and high concentrations of chlorine and hydrochloric acid.
Innovation Solution
A two-step leaching process combining pressure oxidative leaching and atmospheric halide leaching, which eliminates the need for roasting and uses milder conditions with lower halide concentrations, allowing for the recovery of platinum group metals, gold, and silver with reduced reagent costs and process steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional roasting and high concentration HCl leaching is used to extract precious metals, then metal recovery efficiency is improved, but reagent consumption and process cost increase significantly
Solution Approach 1:
The patent changes the chemical parameters of the leaching solution by using halide salts (NaCl, KCl, CaCl2) instead of high concentration HCl, and operates at near-neutral pH (6.5-7.5) instead of highly acidic conditions. This parameter change maintains effective metal extraction while dramatically reducing reagent consumption and cost.
Solution Approach 2:
The patent replaces expensive and hazardous reagents (high concentration HCl, chlorine gas) with cheap, readily available halide salts that can be disposed of more easily. The use of common salts like NaCl and KCl eliminates the need for costly acid handling and disposal infrastructure.
2Reliability
If high concentration HCl and chlorine gas are used for leaching, then oxidation potential is sufficient to extract metals, but safety hazards and environmental harm increase
Solution Approach 1:
The patent converts the previously harmful high-acidity environment into a near-neutral pH environment that is safer and more environmentally friendly. The halide salts provide the necessary oxidation potential without the harmful side effects of concentrated acids and chlorine gas, effectively turning a hazardous process into a benign one.
Solution Approach 2:
The patent creates a chemically inert and safe operating environment by using halide salts in near-neutral pH solutions, eliminating the need for handling highly reactive and hazardous substances like concentrated HCl and chlorine gas. This inert environment maintains effectiveness while removing safety and environmental concerns.
3Device complexity
If sulphur is not removed before leaching, then process steps are reduced, but reagent consumption increases due to sulphur interference
Solution Approach 1:
The patent selectively extracts precious metals from the ore matrix in the presence of sulphur-containing minerals by using halide salts. The selective complexation of precious metals with halide ions allows extraction without prior sulphur removal, taking out only the valuable metals while leaving sulphur in the residue.
Solution Approach 2:
The halide salts act as intermediary agents that facilitate selective metal extraction without requiring complete sulphur removal. The halide ions form stable complexes with precious metals, enabling their separation from the sulphur matrix through controlled precipitation or filtration, thus mediating between the presence of sulphur and the need for clean metal recovery.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves high yields of precious metals with reduced reagent consumption and eliminates the need for costly roasting, making the process more economically viable and efficient in separating precious metals from mineral-based starting materials.
Implementation Method 1
subjecting the starting material to pressure oxidative leaching forming a first solid residue containing precious metals and a first leach solution
Implementation Method 2
subjecting the first solid residue containing precious metals to atmospheric halide leaching, wherein the precious metals are leached into solution forming a second leach solution containing precious metals
Data Source
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AI summary
The invention relates to a method and an apparatus for separating precious metals, especially platinum group metals and gold and silver,and optionally base metals from a starting material containing the same by a combination of pressure oxidative leaching and atmospheric halide leaching.