Cupric Amine Etching for Precious Metal Recovery
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Solution Overview
Problem
Traditional copper etching processes for metal recovery from waste products are limited by the corrosive and toxic nature of acidic cupric chloride solutions and the premature formation of metal oxides, which reduces recovery yields and etching rates.
Innovation Solution
A continuous method using a cupric amine solution with ultrasound energy and controlled temperature to prevent metal oxide formation, allowing for the selective recovery of metals like gold, palladium, and silver from electronic waste by maintaining copper concentration and preventing by-product accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional acidic cupric chloride etchants are used for copper removal, then copper can be removed from waste products, but the process becomes corrosive and toxic, and metal oxide formation prematurely quenches the etching reaction
Solution Approach 1:
The patent changes the chemical parameters of the etchant from traditional acidic cupric chloride to a neutral or slightly alkaline cupric amine solution. This parameter change eliminates the corrosive and toxic characteristics while maintaining the copper removal capability, thereby resolving the contradiction between productivity and harmful factors.
Solution Approach 2:
The patent introduces an amine ligand as an intermediary substance that forms a complex with copper ions in the etchant solution. This intermediary mechanism allows copper removal to proceed without requiring highly acidic conditions, thus eliminating the harmful corrosive and toxic effects while maintaining etching productivity.
2Productivity
If traditional etching processes are used at higher copper concentrations, then copper removal can proceed, but metal oxide formation causes premature quenching of the etching reaction
Solution Approach 1:
The patent changes the pH parameter and chemical composition of the etchant to neutral or alkaline conditions, which prevents metal oxide formation at higher copper concentrations. This allows the etching reaction to continue for extended periods without premature quenching, thereby improving both productivity and duration of action.
Solution Approach 2:
The patent converts the potentially harmful effect of high copper concentrations (which normally cause oxide formation and reaction quenching) into a beneficial condition by using cupric amine complexes that remain stable at high copper levels. This allows the etching process to maintain high productivity throughout extended operation without the harmful oxide formation that would normally limit duration.
3Productivity
If cupric amine solution is used with ultrasound energy to prevent metal oxide formation, then continuous etching can occur, but energy consumption increases
Solution Approach 1:
The patent applies ultrasound energy (mechanical vibration at high frequency) to the cupric amine solution during the etching process. This mechanical vibration prevents metal oxide formation by continuously disrupting the surface and preventing precipitation, thereby enabling continuous etching and improving productivity. The energy consumption is justified by the significant improvement in continuous operation capability.
Solution Approach 2:
The patent uses ultrasound energy as a mechanical field to replace or supplement chemical methods for preventing metal oxide formation. Instead of relying solely on chemical additives or pH control, the mechanical vibration from ultrasound provides an additional mechanism to prevent oxide precipitation, enabling continuous etching with improved productivity despite the energy input.
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 enables continuous etching and optimal collection of desired metals with high purity, overcoming the limitations of traditional processes by reducing oxide formation and maintaining efficient metal recovery.
Implementation Method 1
providing ultrasound energy at a frequency ranging from 15 to 45 KHz, more preferably from 25 KHz to 35 KHz, most preferably from 29.5 KHz to 30.5 KHz that sweeps between 100 to 130 times per second, and has an energy density of 4 to 8 watts per cubic inch. thereby limiting copper oxide (CuO), hydroxides, and other by-product formation on a work face of the electronic waste in an ultrasound equipped tank
Implementation Method 2
contacting the electronic waste with a cupric amine solution to separate the desired metal integrally formed with copper from the substrate and the copper; etching the copper with the cupric amine solution at a temperature ranging from 45° C. to 60° C. for between 40 to 70 hours thereby releasing the desired metal from the substrate and the copper
Implementation Method 3
maintaining copper concentration, predetermined temperature conditions, ultrasound energy conditions (frequency), or any combination thereof to prevent and/or limit metal oxide formation and/or accumulation during the method
Data Source
AI summary
Disclosed is a method for extracting a desired metal contained in electronic waste having a substrate and desired metal integrally formed with copper, the method includes (a) contacting the electronic waste with a cupric amine solution to separate the desired metal integrally formed with copper from the substrate and the copper, and (b) optionally providing ultrasound energy at a frequency ranging from 15 to 45 KHz and at a temperature ranging from 45° C. to 60° C. thereby limiting metallic oxide(s) formation at a surface of a workface; and (c) etching the copper with the cupric amine solution at a temperature ranging from 45° C. to 60° C. for between 40 to 70 hours thereby releasing the desired metal from the substrate and the copper; (d) collecting the released desired metal of step (c).