Colloidal Gold Particles Adsorption onto Silanized Glass Surfaces

Abstract

The adsorption of colloidal gold onto glass surfaces previously treated with bifunctional silanes was studied aiming to enhance the recovery of colloidal gold particles from process water in the mining industry. Colloidal gold samples were prepared via the reduction of gold in HAuCl₄ solution by sodium citrate. Glass plates used as model substrates were silanized with an ethanolic solution of (3‐mercaptopropyl)trimethoxysilane (MPS) and subsequently immersed in the colloidal gold dispersion. The characterization methods used were contact angle measurements to evaluate changes in hydrophobicity; UV/visible spectrometry, to estimate the extent of aggregation of the gold particles; atomic absorption, to measure the amount of gold adsorbed onto the glass plates and scanning electron microscopy (SEM), to estimate the number of colloidal gold particles deposited onto the glass plates. The deposition rate of gold particles on silanized glass surfaces was also studied by using a rotating disk system. It was found that, after the initial deposition of nanometric gold particles, the formation of microaggregates started to take place. After 15 min of immersion time, the microaggregates would act as nuclei for the deposition of new individual particles, leading to the formation of agglomerates bigger than 300 nm. The application of the Levich equation to calculate the rate of deposition of the gold particles showed that the process is not controlled only by diffusion but also by the slow adsorption process itself.

Keywords:

• Colloidal gold adsorption
• Silanized substrates
• Particles deposition
• Gold recovery

Acknowledgments

The authors thank the CNPq, FAPERJ, and FINEP for financial support to this project. They are also indebted to the DCMM of PUC/RJ for the atomic absorption analysis and to José Roberto da Rocha Bernardo for the technical support in the SEM analysis. Thanks are also due to Andrew Bott for revising the English text.