Ammoniacal Solvoleaching of Copper from High-Grade Chrysocolla
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RESEARCH ARTICLE
Ammoniacal Solvoleaching of Copper from High‑Grade Chrysocolla Lukas Gijsemans1 · Joris Roosen1 · Sofía Riaño1 · Peter Tom Jones2 · Koen Binnemans1 Received: 22 June 2020 / Accepted: 14 September 2020 © The Author(s) 2020
Abstract The copper silicate ore chrysocolla forms a large potential copper resource, which has not yet been fully exploited, due to difficulties associated with its beneficiation by flotation and metallurgical processing. Direct acid leaching of chrysocolla causes silica gel formation. Therefore, in this work, the feasibility of solvometallurgical methods to leach copper from highgrade chrysocolla while avoiding issues with silica gel formation was assessed. Ammoniacal solvoleaching was performed with a solvent comprising the chelating extractant LIX 984 N or the acidic extractant Versatic acid 10 in an aliphatic diluent (ShellSol D70 or GTL Fluid G70), combined with a small volume of aqueous ammonia. In the three-phase system, aqueous ammonia dissolves copper from milled and sieved chrysocolla, while copper is simultaneously extracted to the organic phase, releasing ammonia that can be reused for further extraction. The best results were obtained with LIX 984 N as extractant: using a 50 vol% LIX 984 N solution, about 75% of copper could be extracted after 60 min of leaching at 25 °C. The stripping of copper from the pregnant leach solution was optimized. Quantitative stripping of copper was achieved with 1.89 M sulfuric acid and the final aqueous solution of copper sulfate had a concentration of 33 g L −1. Experiments in a leaching reactor (1 L) and small battery of mixer-settlers (3 stages, 35 and 143 mL effective volume in the mixer and the settler, respectively, per stage) were successfully conducted and allowed to recover copper with a purity of 99.9%. A conceptual flow sheet has been developed. Graphical Abstract
Keywords Ammonia · Chelating extractants · Leaching · Solvent extraction · Solvometallurgy
Introduction The contributing editor for this article was U. Pal. * Koen Binnemans [email protected] 1
KU Leuven, Department of Chemistry, Celestijnenlaan 200F, Box 2404, 3001 Leuven, Belgium
KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, Box 2450, 3001 Leuven, Belgium
2
Chrysocolla is a hydrated copper silicate mineral. Until the late 1960s, chrysocolla was considered to be a mixture of a crystalline copper silicate phase dispersed in an amorphous silica hydrogel. Later it was found that chrysocolla is a silicate mineral with formula Cu2–xAlx(H2–xSi2O5)(OH)4·nH2O (x
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