Chloride Leaching Gold Recovery Process
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Solution Overview
Problem
Current gold recovery processes from gold-bearing ores or concentrates often rely on cyanide leaching, which generates toxic waste and poses environmental hazards, and lack effective alternatives for recycling and separating gold from other metals like iron.
Innovation Solution
A process using a lixiviant of hydrochloric acid and magnesium chloride for leaching gold, followed by solvent extraction and stripping with sodium thiosulphate to selectively recover gold, avoiding cyanide and enabling recycling of materials, thus separating gold from iron.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cyanide leaching is used to recover gold from ore, then gold extraction efficiency is improved, but environmental pollution and toxic waste generation worsen
Solution Approach 1:
The patent changes the chemical parameters of the leaching system by replacing cyanide with a chloride-based system (hydrochloric acid and magnesium chloride). This parameter change maintains gold extraction efficiency while eliminating the toxic environmental effects of cyanide, directly resolving the contradiction between productivity and harmful factors
Solution Approach 2:
The patent converts the previously harmful cyanide chemistry into a beneficial chloride chemistry system. By using hydrochloric acid and magnesium chloride, the process achieves effective gold leaching while producing non-toxic waste streams that can be neutralized and recycled, transforming a harmful process into a beneficial one
2Productivity
If cyanide leaching is used, then gold recovery is achieved, but separation of gold from other metals like iron becomes difficult
Solution Approach 1:
The patent changes the chemical selectivity parameters by using chloride-based chemistry instead of cyanide. The chloride system exhibits different complexation behavior with various metals, allowing iron to remain in the aqueous phase while gold is selectively extracted into the organic phase, thereby simplifying the separation process
Solution Approach 2:
The patent introduces an organic extractant as an intermediary phase that selectively transfers gold from the aqueous leach solution to the organic phase. This intermediary extraction step achieves clean separation of gold from iron and other base metals, reducing the complexity of subsequent purification steps
3Productivity
If traditional gold recovery processes are used, then gold is extracted, but recycling of lixiviant and materials is limited
Solution Approach 1:
The patent implements a systematic approach to recovering and recycling materials. The chloride lixiviant (hydrochloric acid and magnesium chloride) is recovered from the aqueous phase after gold extraction and recycled back to the leaching step. The organic extractant is also regenerated and reused, minimizing material loss and reducing operational costs
Solution Approach 2:
The patent establishes feedback loops in the process where spent lixiviant and extractant are continuously recovered, purified, and fed back into the respective process steps. This closed-loop system ensures high levels of material recycling and minimizes waste discharge, directly addressing the recyclability issue
4Productivity
If cyanide-based processes are used, then gold leaching is effective, but operational safety and environmental compliance costs increase
Solution Approach 1:
The patent fundamentally changes the chemical safety parameters by replacing cyanide with non-toxic chloride chemistry. The hydrochloric acid and magnesium chloride system maintains effective gold leaching while eliminating hydrogen cyanide gas formation and cyanide toxicity, thereby reducing operational hazards and environmental compliance costs
Solution Approach 2:
The patent transforms the previously harmful cyanide system into a safe chloride system. The chloride chemistry provides effective gold dissolution while producing environmentally benign waste streams that can be easily neutralized and disposed of, or better yet, recycled back into the process, eliminating safety and compliance burdens
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 gold recovery rates with minimal environmental impact by using chloride chemistry at atmospheric pressure, allowing for the selective extraction and recycling of gold and iron, reducing toxic waste and operational costs.
Implementation Method 1
leaching the gold-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride
Implementation Method 2
subjecting the leach solution so obtained to a liquid/solids separation step... subjecting the liquid obtained in step b) to an organic solvent extraction step
Implementation Method 3
stripping gold from the pregnant organic solvent extractant solution obtained in step c) with sodium thiosulphate
Implementation Method 4
recovering gold by precipitating gold from the aqueous solution obtained in step d)
Data Source
AI summary
A process for the extraction of gold from a gold-bearing ore or concentrate, comprising the steps of leaching the gold-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride at atmospheric pressure at a temperature of at least 90° C. and an Eh of at least 900 mV. After a liquid/solids separation step, the solution obtained is subjected to an organic solvent extraction step using an oxime to obtain a solution of organic solvent containing gold, which is stripped with sodium thiosulphate to recover gold. The extraction may be operated to extract gold with or without iron. Materials used in the process may be recycled. The process avoids environmental and other hazards associated with the use of cyanide to extract gold.