Application of electrodialysis technique to recover contaminated rinsing water from gold electroplating processes

Abstract

The aim of the present work was to evaluate the possibility of using an electrodialysis technique to recover rinsing water contaminated with the electrolyte during the process of gold electrodeposition. During the rinsing process the electrolyte, containing gold, silver, cyanide and contaminants, is dragged from the bath with the plated components. The more the rinsing water is used the more it becomes concentrated and therefore water replacement is necessary. In these studies three different types of electrodialysis cell containing two, three and five separate compartments were used. Two kinds of ion selective membranes, a cationic Nafion 450 and an anionic Selemion AMV, were used in the construction of the cells. The total cell potential, membrane potential and polarisation potential as a function of applied current were evaluated. The results show that it is possible to extract an average of 56% of all metal and cyanide from the rinse water working at 30 mA cm⁻² for 190 h. However, a more efficient extraction of 75% of all the metals and cyanide was obtained within 270 min of electrodialysis at a current density of 20 mA cm⁻². The results of this study showed that electrodialysis is suitable for removing contaminants from rinsing water to be returned to the process.

Keywords:

• Electrodialyses
• Water recycling
• Gold
• Rinsing water
• Electroplating

The authors would like to thank DOCOL Industry for the donation of the gold solution, DADP/FURB for their financial support and LACOR/UFRGS, GEAM/FURB and PPGEA for technical support and laboratory facilities.