Oxime Extractant Stability in Nitrate-Rich Solvent Extraction
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Solution Overview
Problem
Solvent extraction reagents, particularly oxime and ketoxime, used in metal recovery processes are prone to degradation when exposed to nitrate-containing feeds, leading to reduced efficiency in metal transfer from leach solutions to strip solutions, especially in ores with high nitrate concentrations like those found in the Atacama Desert region of Chile.
Innovation Solution
The use of organic soluble anti-degradation agents in combination with modified or unmodified salicylaldoxime and/or ketoxime extractants to reduce nitration and hydrolysis rates during metal extraction and stripping processes, employing a solvent extraction composition comprising a water-immiscible organic solvent, orthohydroxyarylaldoximes, and anti-degradation agents like phenols to stabilize the reagents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxime reagents are used in metal extraction circuits, then copper recovery efficiency is improved, but reagent stability deteriorates due to nitration and hydrolysis in nitrate-containing feeds
Solution Approach 1:
The patent introduces anti-degradation agents (such as phenolic compounds, carboxylic acids, or their derivatives) as intermediary substances that mediate between the oxime reagent and the nitrate-containing feed. These agents preferentially react with nitrating species or form protective complexes, shielding the oxime reagent from degradation while maintaining its copper extraction functionality.
Solution Approach 2:
The patent creates a composite reagent system by combining oxime extractants with anti-degradation agents in specific formulations. This composite approach allows the system to simultaneously exhibit high copper extraction efficiency (from the oxime) and enhanced stability against nitration and hydrolysis (from the anti-degradation agent), resolving the contradiction between productivity and reliability.
2Reliability
If operational adjustments are made to reduce degradation (e.g., reducing nitrate concentration, raising pH), then reagent stability is improved, but process complexity and cost increase
Solution Approach 1:
Instead of making complex operational adjustments to process parameters (nitrate concentration, pH, redox potential), the patent changes the chemical composition parameter by adding anti-degradation agents to the reagent formulation. This allows the system to maintain high stability while operating under conventional process conditions, avoiding increased complexity in the extraction circuit flow sheet.
3Reliability
If ketoxime reagents with higher stability are used, then resistance to nitration and hydrolysis is improved, but copper extraction efficiency decreases due to weaker reagent strength
Solution Approach 1:
The patent merges the advantages of different reagent types by combining oxime extractants (which provide high copper extraction efficiency) with anti-degradation agents (which provide resistance to nitration and hydrolysis). This combination allows the system to achieve both high productivity and high reliability, overcoming the limitation of using ketoximes alone which sacrifice extraction efficiency for stability.
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
The proposed solution significantly enhances the stability of oxime reagents against nitration and hydrolysis, maintaining high copper recovery efficiency even in low pH and high nitrate conditions without requiring costly adjustments to the pregnant leach solution, thus improving the overall metal extraction process.
Implementation Method 1
the compositions in accordance with the invention are resistant to nitration and hydrolysis when used in the presence of these nitrate containing feeds
Implementation Method 2
the compositions in accordance with the invention are resistant to nitration and hydrolysis when used in the presence of these nitrate containing feeds
Implementation Method 3
Solvent extractants are well known for the recovery of metals, especially copper, from aqueous streams
Data Source
AI summary
A solvent extraction composition and process for using the composition is provided. The composition contains up to 70% by weight of at least one orthohydroxyarylketoxime extractant and /or at least one orthohydroxyarylaldoximes extractant, salts and mixtures thereof; from about 0.1 to about 20 % by weight of at least one substantially water insoluble aromatic hydroxy containing antidegradation agents. The composition optionally contains an equilibrium modifier.