Precious Metal Purification via Bromide Oxidation and Cyclodextrin Precipitation
Solution Overview
Problem
Current methods for recovering precious metals like gold, silver, platinum, and palladium are environmentally harmful due to the use of cyanide and are inefficient for refractory ores with high sulfur content, posing health risks and environmental contamination.
Innovation Solution
A method involving an aqueous acidic oxidant mixture of hydrogen peroxide and bromide ions is used to oxidize precious metals, forming a metal bromide salt solution, which is then adjusted with alkali metal ions and cyclodextrin to precipitate a metal cyclodextrin complex, allowing for the recovery of gold, silver, platinum, and palladium while leaving other metals in solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cyanide leaching process is used for precious metal recovery, then metal extraction efficiency is improved, but environmental contamination and health risks worsen
Solution Approach 1:
The patent changes the chemical parameters of the leaching process by replacing cyanide with alternative reagents such as thiosulfate, thiocyanate, or halide complexes. This substitution maintains the extraction efficiency while eliminating the toxic effects of cyanide, directly resolving the contradiction between productivity and environmental safety
Solution Approach 2:
The patent employs readily available, non-toxic reagents that can be easily disposed of or degraded in the environment, replacing the persistent and toxic cyanide. These alternative chemicals provide sufficient extraction capability without creating long-term environmental hazards
2Adaptability or versatility
If conventional cyanide-based processes are used, then gold and silver recovery is achieved, but other precious metals such as platinum and palladium are not extracted
Solution Approach 1:
The patent develops a universal leaching system using alternative reagents that can simultaneously extract multiple precious metals including gold, silver, platinum, and palladium. The modified chemical environment created by reagents like thiosulfate or halide complexes provides broad metal solubility, enabling one process to handle diverse metal recovery needs
3Productivity
If refractory ores with high sulfur content are treated by conventional methods, then processing is simplified, but metal extraction efficiency deteriorates
Solution Approach 1:
The patent modifies the chemical parameters of the leaching process by using alternative reagents that are effective against sulfur-containing refractory ores. These reagents create chemical environments that prevent sulfur from interfering with metal extraction, thereby improving productivity without requiring complex pre-treatment processes
Solution Approach 2:
The patent introduces alternative complexing agents as intermediaries that facilitate metal extraction from refractory ores. These intermediary chemicals bridge the gap between the ore matrix and the metal ions, enabling efficient extraction even in the presence of sulfur compounds that would normally hinder the process
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 effectively recovers precious metals with high yield and selectivity, reducing environmental impact and health risks, and is particularly effective for refractory ores, achieving higher extraction levels than conventional cyanide-based processes.
Implementation Method 1
forming an aqueous acidic oxidant mixture from hydrogen peroxide an acid and a source of bromide ion... to oxidise the metal and form a metal bromide salt solution
Implementation Method 2
adding cyclodextrin to the alkali metal/metal bromide salt solution to precipitate a metal cyclodextrin complex
Data Source
AI summary
This invention relates to methods for the recovery of precious metals such as gold, silver, platinum, palladium and rare earths from precious metal-bearing materials.In particular, a method of purifying precious metal from a precious metal-bearing material comprising the stepsa) forming an aqueous acidic oxidant mixture from hydrogen peroxide an acid and a source of bromide ion, said acidic oxidant mixture having a pH in the range 0 to 6;b) contacting the acidic oxidant mixture with the precious metal bearing-material to oxidise the metal and form a metal bromide salt solution containing the metal bromide MBrn and/or [MBrn+1]− where n is the valency of the oxidised metal ion Mn+; andc) controlling the metal bromide salt solution to a value in the range 3-7 by providing alkali metal ions A+ in the solution to form an alkali metal/metal bromide solution containing the salt AMBrn+1 in solution.