Microwave-Assisted PGM Leaching with Reduced HCl and NaCl
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Solution Overview
Problem
Existing microwave-assisted leaching processes for Platinum Group Metals (PGMs) require high concentrations of chemicals, leading to hazardous waste and long processing times, and often necessitate additional oxidation agents, which are harmful and inefficient.
Innovation Solution
A method utilizing an aqueous leaching solution with reduced concentrations of HCl (0.25 M to 5 M) and NaCl (0.5 M to 5 M), heated by microwaves to 120 °C to 250 °C, with a liquid-to-solid ratio of 5 to 10, to extract PGMs efficiently without additional oxidation agents, reducing chemical use and processing duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high concentrations of HCl and oxidation agents are used for leaching, then PGM extraction efficiency is improved, but chemical waste and safety hazards increase
Solution Approach 1:
The patent changes the concentration parameters of chemicals used in leaching. Instead of using high concentrations of HCl (typically 6-12 M) and oxidation agents, the invention uses reduced concentrations (0.25-5 M HCl) combined with microwave energy, thereby maintaining extraction efficiency while reducing chemical waste and safety hazards
Solution Approach 2:
The patent substitutes chemical oxidation agents with microwave energy for heating and activating the leaching process. This replacement reduces reliance on harmful chemicals like H2O2, HNO3, or Cl2, thereby decreasing chemical waste and safety hazards while maintaining or improving extraction efficiency
2Device complexity
If traditional heating methods are used for leaching, then process simplicity is maintained, but energy consumption increases
Solution Approach 1:
The patent replaces traditional external heating methods (fire, steam, electric heaters) with microwave heating technology. Microwaves directly heat the leaching solution and solid material through dielectric heating, significantly reducing energy consumption and processing time while adding minimal complexity to the overall process
3Reliability
If long leaching durations are used, then extraction completeness is improved, but productivity decreases
Solution Approach 1:
The patent employs periodic or pulsed microwave heating during the leaching process. Intermittent microwave irradiation with appropriate duty cycles enhances mass transfer and reaction kinetics, achieving complete extraction in shorter times (minutes rather than hours) compared to continuous traditional heating
Solution Approach 2:
The patent utilizes phase transitions induced by microwave heating to enhance leaching efficiency. Rapid heating causes localized boiling and cavitation effects that improve contact between leaching solution and solid material, accelerating extraction without requiring extended processing times
4Loss of substance
If reduced chemical concentrations are used, then waste reduction is achieved, but extraction efficiency may decrease
Solution Approach 1:
The patent substitutes chemical energy (from high-concentration reagents) with electromagnetic energy (microwaves) to drive the leaching process. This substitution enables the use of reduced chemical concentrations while maintaining extraction efficiency, as microwaves provide the activation energy needed for effective leaching at lower reagent levels
Solution Approach 2:
The patent changes multiple parameters simultaneously: reduces chemical concentration, introduces microwave power density as a new parameter, optimizes heating rate and temperature profile. This multi-parameter optimization ensures that extraction efficiency is maintained despite reduced chemical usage
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
Achieves high extraction yields of at least 60% for PGMs like Pt, Pd, and especially Rh, with reduced chemical usage and energy consumption, while minimizing the extraction of other elements, thus enhancing selectivity and safety.
Implementation Method 1
The aqueous leaching solution comprising the product is heated to a temperature between 120 °C and 250 °C by means of MW heating
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3~4
AI summary
The present invention relates to a microwave (MW) assisted leaching method (1) for extracting a PGM from a PGM-comprising product, comprising: providing (2) an aqueous leaching solution comprising HCl and NaCl; adding (3) a product comprising a PGM to the aqueous leaching solution; heating (4) the aqueous leaching solution to a temperature between 120 °C and 250 °C by means of MW heating, thereby obtaining a slurry comprising a leachate comprising the PGM and a solid residue; cooling (5) the slurry; and separating (6) the leachate from the solid residue, thereby obtaining the extracted PGM; wherein the concentration of HCl, NaCl and chloride anions in the aqueous leaching solution is between 0.25 M and 5 M, between 0.5 M and 5 M, and equal to or higher than 2 M, respectively.