Multi-Stage Solvent Extraction for Dilute Gold Recovery
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Solution Overview
Problem
Current methods for recovering gold from aqueous solutions with low gold concentrations, such as those produced in wet copper smelting, are inefficient and environmentally harmful due to the use of expensive and toxic chemicals like cyan compounds, and the solvent extraction process is not applicable to concentrations below 10 mg/L.
Innovation Solution
A multi-stage solvent extraction process using dibutyl carbitol (DBC) as the extraction medium, where the medium is recycled multiple times without back extraction, and the volume ratio of DBC to aqueous solution is optimized to achieve high gold concentration in the extraction medium, allowing for efficient gold recovery from solutions with concentrations as low as 10 mg/L.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If activated carbon adsorption is used to recover gold from dilute solutions, then gold recovery is achievable, but the process requires expensive and toxic chemicals (cyan compounds, thiourea, thiosulfuric acid) for elution
Solution Approach 1:
The patent changes the concentration parameter threshold by enabling solvent extraction to work at gold concentrations of 10 mg/L or lower, which was previously below the applicable range. This parameter change allows the use of environmentally friendly extraction agents instead of toxic chemicals while maintaining effective gold recovery
Solution Approach 2:
The patent replaces expensive and toxic elution chemicals (cyan compounds, thiourea, thiosulfuric acid) with a more economical and environmentally friendly approach using solvent extraction followed by simple reduction, eliminating the need for costly chemical elution processes
2Productivity
If solvent extraction process is used for gold recovery, then the process is simple and fast, but it is not applicable to solutions with gold concentration below several grams per liter
Solution Approach 1:
The patent extends the applicable concentration range of solvent extraction by optimizing the volume ratio of extraction medium to aqueous solution to 1/5 or smaller, enabling the process to effectively handle gold concentrations of 10 mg/L or lower while maintaining its inherent advantages of simplicity and speed
Solution Approach 2:
The patent applies preliminary concentration of gold in the aqueous solution before solvent extraction, creating conditions that enable the subsequent extraction process to operate efficiently even when starting from very dilute solutions, thus expanding the process adaptability
3Reliability
If activated carbon is combusted to recover gold, then gold can be obtained, but the activated carbon cannot be recycled and waste gas treatment is required
Solution Approach 1:
The patent recovers the extraction medium after gold extraction and reuses it for subsequent extraction operations, eliminating waste and reducing costs. The medium is regenerated through simple filtration and reduction processes, enabling continuous cyclic operation without disposal
Solution Approach 2:
The extraction medium performs multiple functions: extracting gold from dilute solutions, concentrating it to recoverable levels, and then being easily regenerated through filtration and reduction. The system is self-sustaining with the medium serving itself through cyclic reuse without requiring external disposal or replacement
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 efficient gold recovery from dilute solutions without the need for toxic chemicals, reducing processing time and costs, and simplifies the refining process, achieving high gold purity and recovery ratios.
Implementation Method 1
a multi-stage solvent extraction process using dibutyl carbitol (DBC) as the extraction medium
Implementation Method 2
the extracted gold may be recovered only by reduction
Data Source
AI summary
Disclosed is a method of recovering gold from an aqueous solution having a gold concentration of 10 mg/L or lower, using a plurality of extraction apparatuses for bringing the aqueous solution into contact with an extraction agent, arranged to configure a multi-stage extraction process, the method allowing the aqueous solution to continuously flow from the first-stage extraction process to the next-stage extraction process, while recycling the extraction medium used in each stage twice or more times for the extraction process of the same stage, without back extraction and reduction.