Hypochlorite Gold Extraction Reduces Halogen Consumption
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Solution Overview
Problem
Existing gold and silver extraction methods using halogens face challenges such as contamination of brine solutions, low solubility of chlorine in water, and increased halogen consumption due to secondary reactions with base metals and sulfur, requiring improved methods for efficient precious metal recovery and halogen recycling.
Innovation Solution
A method involving the use of diluted hypochlorites as a source of active chlorine, with a diaphragm-less electrolytic cell and acidic conditions to control the oxidation-reduction potential, allowing for efficient gold and silver extraction by generating hypohalites from salt brine, which are highly soluble and reduce secondary reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If elemental chlorine is used for gold extraction, then precious metals recovery is fast and complete, but halogen consumption increases due to secondary reactions with base metals and sulfur
Solution Approach 1:
The patent changes the chemical form of halogen from elemental chlorine (Cl2) to hypohalite ions (OCl-), which fundamentally alters the reaction kinetics and selectivity. This parameter change reduces secondary reactions with base metals and sulfur while maintaining effective gold extraction, thereby reducing halogen consumption.
Solution Approach 2:
The patent introduces hypohalite ions as an intermediary species that mediates the oxidation process. Instead of direct chlorine attack on gold, the hypohalite ion serves as the active extracting agent, providing more selective and controlled oxidation that minimizes unwanted side reactions with other minerals.
2Reliability
If brine is purified extensively prior to electrolysis, then diaphragm materials are protected from contamination, but process complexity and cost increase
Solution Approach 1:
The patent employs disposable or replaceable diaphragm materials that can withstand contamination without requiring extensive purification of the brine. This approach accepts short-term contamination tolerance in exchange for simplified overall process design, eliminating complex purification steps while maintaining operational reliability through periodic diaphragm replacement.
3Loss of time
If chlorine solubility in water is increased, then chlorine addition time is reduced, but chlorine solubility in brine is inherently low
Solution Approach 1:
The patent changes the chemical form from molecular chlorine (Cl2) to hypohalite ions (OCl-), which have significantly higher solubility in aqueous brine solutions. This parameter change eliminates the solubility limitation, allowing rapid and complete delivery of the extracting agent without prolonged addition times.
Solution Approach 2:
The patent uses hypohalite ions as a soluble intermediary that bridges the gap between gaseous chlorine and the aqueous brine system. This intermediary form dissolves readily in brine and then delivers the oxidizing power needed for gold extraction, effectively bypassing the solubility barrier of molecular chlorine.
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 approach significantly reduces halogen consumption, accelerates the extraction process, and allows for near-complete recovery of precious metals with improved solubility and reduced contamination, achieving higher efficiency and halogen recycling.
Implementation Method 1
This production of chlorine is done by the electrolysis of the brine in a standard electrolytic cell with either a membrane or a diaphragm for the separation of the cathodic compartment from the anodic one
Implementation Method 2
The high oxidation potential of the chlorine leads to the formation of some bromine from the bromide in the slurry, and the mixed halogens (chlorine, bromine) lead to a fast (a few hours) and rather complete precious metals recovery
Data Source
AI summary
The invention relates to a method for the extraction of precious metals, using halogens. It has been found that introducing halogens in the reactor in the form of hypohalites rather than free halogens simplified greatly the recycling of halogens by electrolysis. It increases the rate of addition of the halogens and significantly reduces secondary reactions with base metals such as iron. Operating under acidic conditions, the gold recovery has been found as high with hypochlorite as with elemental chlorine, with an active chlorine to ore ratio reduced by a factor of two to five.