Investigation of Reduction and Precipitation Rate of Colloidal Gold Particles Obtained in the Process of Electrical and Electronic Waste Recycling

This paper studies the influence of process parameters: temperature, the weight of the added precipitant agent, pH and reducing agent on the kinetics of the process of reduction and precipitation of gold of 98.44% purity obtained in the process of electrical and electronic waste recycling. The optimal conditions of reduction and precipitation of colloidal gold particles in the process of recycling of different waste types in order to obtain high-purity gold are the following: an optimal process time (τ = 11minutes), temperature (t=5°C), the weight of the added precipitant (m = 6g of pure gold) and K2S2O5 as the preferred reducing agent. The results have contributed to a better understanding of reduction and precipitation rate of colloidal gold particles in order to manage and control this process. The granulometric analysis confirms the existence of colloidal gold particles. SEM analysis indicates spherical particles and good homogeneity of the sample. XRF analysis shows that gold obtained in this process of recycling is highly pure (99.99%).