Copper Enrichment in Solid with Selective Reverse Leaching with Oxalic Acid
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RESEARCH ARTICLE
Copper Enrichment in Solid with Selective Reverse Leaching with Oxalic Acid M. Deniz Turan2 · Zeynel Abidin Sarı1 · Murat Erdemoğlu3 Received: 4 May 2020 / Accepted: 27 July 2020 © The Minerals, Metals & Materials Society 2020
Abstract As the first part of a novel process proposed for copper extraction, selective dissolution of iron from chalcopyrite in oxalic acid solutions with hydrogen peroxide was studied. Despite the fact that both iron and copper are readily soluble in acidic conditions, it was found that oxalic acid provides altered solubility behaviors for these metals. It should be used to form iron (II) oxalate which has a higher solubility (0.008 g/100 g H 2O at 293 K) than copper oxalate (2.16 × 10–10 g/100 g H2O at 293 K), while hydrogen peroxide was used to provide an oxidative leaching environment to break the chalcopyrite structure. Under the examined leaching conditions where 100 g/L of H2C2O4, 3 M of H2O2, 318 K of leaching temperature, 120 min of leaching time, 25 mL/g of liquid–solid ratio, and 400 rpm of stirring speed were applied, extraction rates of copper and iron from the chalcopyrite concentrate were almost 1.5% and 70%, respectively. Copper was found as a solid oxalate form in the residue obtained after the leaching process in these conditions. Graphical Abstract
Keywords Chalcopyrite · Iron dissolution · Oxalic acid · Iron oxalate · Copper oxalate
Introduction
The contributing editor for this article was D. Panias. * M. Deniz Turan [email protected]
Copper is found in the earth’s crust in the form of sulfide, oxide, and carbonate minerals, and very rarely as a native metal. As a result of increasing copper consumption in the world, the cut-off grade of copper ore deposits has significantly decreased in the last 40 years, so that shipping costs
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Journal of Sustainable Metallurgy
for low-grade copper ores (less than 2% Cu) dictate that the concentration facility must be located at the mine site [1]. Extraction of metallic copper from copper ores is economically maintained by a conventional pyrometallurgical process which includes several extraction stages as (a) froth flotation of low-grade copper ore to produce copper sulfide concentrate with approximately 28% Cu, (b) smelting the copper concentrate in a reverberator to obtain molten Cu matte, (c) converting the Cu matte to get impure molten copper, and (d) electrorefining the impure copper to produce ultra-pure copper. On the other hand, various undesirable environmental problems such as SOx emission which causes acid rains occur during application of this pyrometallurgical method which requires high temperatures maintained by burning fossil fuels. Mainly depending on increasing costs of copper extraction from low-grade ores containing sulfides like chalcopyrite (CuFeS2) and bornite ( Cu5FeS4) and adverse environmental effects arising during smelting, leaching in acidic or alkaline aqueous solutions
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