Abstracts Category : Other

The use of surfactants to aid and improve the leaching of low grade copper ores

by Kush Shah

Copper heap leach operations often suffer from reduced efficiency due to long leach times and variable recoveries. Surfactants have been considered as an option in increasing the leachability of ores. Improvements in overall copper extraction have been noted with their use, though testing has only been conducted on a limited scale. The molecular function of surfactants in heap leaching has not been extensively studied and is not well explored. The work in this thesis was aimed at better understanding and characterizing the function of the surfactants. Work was performed with surfactants developed by BASF specifically for heap leaching.Initial experimentation consisted of using flooded vats to compare copper extraction from ores. Leach solution with and without surfactant was fed to the ores. The presence of surfactants was noted to increase the overall copper recovered by approximately 2-3%. Interfacial tension measurements were performed to determine the changes imparted onto the acidic leach solution by the surfactants. Hanging drops were used to determine the activity at the air-liquid boundary. It was found that at the surfactant concentrations used in heap leaching, the interfacial tension of the fluid changed very little, from about 71 mN/m to 69.5 mN/m. The contact angle was determined to better understand the interaction between the acidic media and the ore. This was obtained using capillary wicking and Washburns equation. Ore was finely ground and packed into particle beds. Leach liquid with surfactant was introduced to these beds. The rate of permeating fluid flow was monitored against time. The affinity of the liquid for the solid surface dictated the rate of uptake. Washburns equation allowed for the contact angle to be calculated from these results. It was found that surfactants lowered the contact angle of liquid on solid by up to 3 degrees. The combination of results indicated that the surfactants increases the affinity between the solid and liquid by reducing the contact angle. In a heap, this allows acid to ingress further into sub-surface regions of ore particles. As a result, leachability of the ore is increased as harder to reach minerals can be accessed.