Microfluidic Platform for High-Throughput Screening of Leach Chemistry

Area of Science:

• Materials Science
• Chemical Engineering
• Analytical Chemistry

Background:

• Thiosulfate leaching is crucial for gold recovery.
• Understanding factors affecting gold dissolution is essential for process optimization.
• Existing methods lack in situ monitoring and rapid screening capabilities.

Purpose of the Study:

• To develop and demonstrate a microfluidic platform for in situ monitoring of gold leaching.
• To investigate the impact of various parameters on thiosulfate leaching of gold.
• To determine the activation energy for the gold leaching process.

Main Methods:

• Utilized a transparent microfluidic channel for gold leaching experiments.
• Employed in situ optical monitoring to track gold thickness.
• Systematically varied reagent concentrations, temperature, and film preparation methods.

Main Results:

• Identified critical importance of leach solution preparation, gold film deposition/annealing, and lixiviant chemistry.
• Observed depth-dependent density in sputter-deposited gold films, affecting leach rates.
• Determined optimal lixiviant composition: 10 mM CuSO4, 1 M Na2S2O3, 1 M NH4OH.
• Found annealing above 270 °C prevents leaching due to chromium diffusion.
• Calculated an apparent activation energy of ~40 kJ mol-1.

Conclusions:

• The microfluidic platform enables efficient screening and optimization of gold leaching parameters.
• Precise control over gold film properties and leach solution chemistry is vital for predictable leaching.
• Established a quantitative understanding of thiosulfate leaching kinetics for gold.