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Quantitative SHINERS analysis of temporal changes in the passive layer at a gold electrode surface in a thiosulfate
Scott R Smith1, J Jay Leitch1, Chunqing Zhou1
1†Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Analytical Chemistry
|March 10, 2015
Summary
Shell-isolated gold nanoparticles (SHINs) enable detailed analysis of gold leaching passive layers. SHINERS reveal elemental and polymeric sulfur inhibit gold dissolution in thiosulfate solutions.
Area of Science:
- Electrochemistry
- Materials Science
- Spectroscopy
Background:
- Gold leaching in thiosulfate solutions is crucial for gold recovery.
- Passive layer formation can inhibit gold dissolution, impacting process efficiency.
- Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) offers high sensitivity for surface analysis.
Purpose of the Study:
- To analyze the passive layer formed during gold leaching in thiosulfate solutions using SHINERS.
- To develop a method for compensating for signal fluctuations in SHINERS.
- To identify the chemical species responsible for passive layer formation and gold dissolution inhibition.
Main Methods:
- Coating gold nanoparticles with a silica layer using (3-aminopropyl)triethoxysilane (APTES) and sodium silicate to create SHINs.
- Utilizing SHINs to record SHINERS of the passive layer on a gold electrode in thiosulfate solutions.
- Employing APTES bands as an internal standard for signal correction and developing a method for their removal.
Main Results:
- SHINERS spectra revealed bands indicative of hydrolyzed APTES within the passive layer.
- A novel method was established to use APTES bands as an internal standard for SHINERS signal normalization.
- The passive layer was identified to comprise elemental sulfur (cyclo-S8) and polymeric sulfur chains.
Conclusions:
- The developed SHINERS methodology allows for accurate analysis of passive layers in gold leaching.
- Elemental sulfur and polymeric sulfur chains are key components of the passive layer that inhibit gold dissolution.
- Understanding these species is vital for optimizing gold recovery processes in thiosulfate media.
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