Use of quillaja saponins (Quillaja saponaria Molina) to control acid mist in copper electrowinning processes. Part 1: Laboratory scale evaluation

摘要

This work describes the use of extracts of the Chilean quillaja tree (Quillaja saponaria Molina) as alternative low cost surfactants for the control of acid mist in copper electrowirming (EW). Quillaja extracts contain triterpenoid saponins, which are natural surfactants traditionally used as foaming agents in food and beverages. Two commercial products with different degrees of purification were tested: QL 1000~R (non-refined product, 8.4 percent saponin content) and Mistop~R (refined product, 16 percent saponin content). Laboratory experiments determined the effects of both products on electrolyte surface tension (ST), solvent extraction process (SX), current efficiency (CE) and cathode quality. A surface tension of 55 dyn/cm was attained with 10 ppm of Mistop~R and 25 ppm of QL 1000~R, respectively. This corresponded to similar saponin levels for both products (1.6-2.1 ppm saponins). At these concentrations, Mistop~R had little negative impact on the SX process, and no effect on CE and cathode quality. However, QL 1000~R had a negative impact on phase disengagement time and extraction efficiency. Based on this, Mistop~R was recommended for further testing at pilot plant and industrial scale in the facilities of Radomiro Tomic copper mine (Calama, Chile), at a dose of 8 to 12 pprn.