Enrichment of platinum group metals (PGMs) by two-stage selective pressure leaching cementation from low-grade Pt-Pd sul
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JINBAOSHAN proterozoic platinum mine (Yunan Province, People’s Republic of China) is the second largest platinum mine in China. It is estimated that the mine has a potential reserve of 45.3 tons of Pt 1 Pd with a chemical composition of (Pt 1 Pd) 1.45 g/t, Cu 0.08 pct, Ni 0.17 pct, S 0.61 pct, and Fe 9.88 wt pct. After flotation processing, the content of (Pt 1 Pd) increased from 1.45 g/t (crude) to 86 g/t (as-is flotation sulfide concentrates). The as-is flotation concentrates cannot be sold either as CuNi or precious metal concentrates due to their low metal value. Thus, further enrichment treatment will be required in order to produce marketable concentrate products. Since 1998, various processing options have been proposed for recovering the precious metals from the flotation sulfide concentrates. The major three approaches are as follows: (1) traditional pyrometallurgical process to enrich precious metals into Cu-Ni matte, which is similar to the process being used in INCO, Impala, and Jinchuan smelter’s operations; (2) hydrometallurgical acidic oxidizing leaching at atmosphere pressure; and (3) two-stage process of selective pressure acidic leaching-pressure cyanidation leaching. Preliminary extraction studies[1,2,3] show that the following: (1) the pyrometallurgical process (option 1) is not suitable to treat concentrates containing low sulfur and high MgO; (2) atmospheric acidic leaching (option 2) is not technically sound due to its poor performance in recovery and efficiency; and (3) selective two-stage pressure leaches KUN HUANG, Vice-Professor, JING CHEN, Professor, YI-RAN CHEN, JIA-CHUNG ZHAO, QI-WEI LI, and QIU-XUE YANG Engineers, are with the College of Chemistry and Material Engineering, Yunnan University, Kunming 650092, Yunnan, People’s Republic of China. Contact e-mail: [email protected]. YONG ZHANG, Professor, is with Colt Engineering, Edmonton, AB, Canada T6J 4Y3. Manuscript submitted June 6, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS B
(option 3) are preferred because of their advantages such as capability to handle low-grade concentrates, high metal recovery, short process unit operations, low capital investment, and SO2-free environment. Since 1998, option 3 has been tested at both lab and pilot scales with the patent granted in China.[10] Studies[3,10] on option 3 indicated the following. (1) The two-step hydrometallurgical process is able to handle concentrates containing low sulfur and high MgO. This allows the flotation plant to produce a high MgO concentrate without a huge rejection of impurity fractions. This helps to maintain a high flotation yield, i.e., metal recovery. (2) Precious metals can be enriched in iron residues and separated from base metals via applying the commercial pressure acidic leaching process with low risk. Acidic pressure leaching has been successfully applied for processing of Cu-Ni sulfide concentrates and laterite (Dynatec, Sherritt Int., CESL, INCO, etc.) and preoxidation of refractory gold concentrates (American Barrick). Compared with atmospheric leac
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