Assessing a two-stage heap leaching process for Platreef flotation concentrate

Mwase, James M.; Petersen, Jochen; Eksteen, Jacques

doi:10.1016/j.hydromet.2012.09.007

Cited by 32 publications

(21 citation statements)

References 26 publications

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“…This is opposite to what was observed in earlier test work on concentrate (Mwase et al, 2012a;Mwase et al, 2012b) in which the extent and rate of extraction Ni was higher than Cu. It is suggested that in the concentrate leaching galvanic leaching facilitated almost complete extraction of Ni and faster leaching than Cu.…”

Section: Column Bioleachingcontrasting

confidence: 99%

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A novel sequential heap leach process for treating crushed Platreef ore

2014

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A novel sequential heap leaching process has been identified as a possible alternative to the conventional concentrate-smelt-refine route for processing Platreef ore, a platinum group metals containing ore with palladium predominance. The present study focuses on testing this process on crushed whole ore, after initial experiments conducted on low-grade Platreef flotation concentrate achieved promising results. Two samples of drill core Platreef ore with size distributions of -25 mm +1 mm and -6 mm +1 mm were first bioleached in cylindrical columns, to simulate heap leaching, at 65°C and then leached with cyanide solution at 50°C in cylindrical columns. Overall the best results were achieved from the tests on the -6 mm +1 mm size fraction sample. After 304 days 93% Cu, 75% Ni and 53% Co were extracted in the bioleach experiment, and after 60 days 57.8% Pt, 99.7% Pd and 90.3% Au in the follow-up cyanide leach experiment. Analysis using a mineral liberation analyser suggested that Pt and Pd were leached mostly from the tellurides while the Pt arsenides appeared resistant to cyanide leaching. From the results it is proposed that the process considered herein is a potential alternative route to treat Platreef ore.

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Section: Column Bioleachingcontrasting

confidence: 99%

“…In the first phase of this study, test work was conducted on lowgrade Platreef concentrate which served as a proxy material (Mwase et al, 2012a). This was done to facilitate a faster turn around of results and to establish optimal conditions for operating before proceeding to test the process on coarse ore.…”

Section: Introductionmentioning

confidence: 99%

A novel sequential heap leach process for treating crushed Platreef ore

2014

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“…A two-stage heap leaching process was developed as an alternative to the conventional concentrate-smelt-refine process to treat Platreef ore (Mwase et al, 2014;Mwase et al, 2012;Eksteen et al, 2012). The process consists of a thermophile heap bioleaching stage which removes large portions of Cu, Ni and Co from the ore for separate recovery and nearly completely oxidises all sulphide present.…”

Section: Introductionmentioning

confidence: 99%

“…This is followed by a cyanide leach stage at 50°C which intends to mobilise Au, Pd and Pt. The process was tested at laboratory scale using columns to simulate heap conditions (Mwase et al, 2014;Mwase et al, 2012). While the bioleaching stage achieved the desired performance, the cyanide leaching rapidly mobilised Pd quantitatively and 90% of Au, but only 60% of the Pt was extracted over a 60 day period.…”

Section: Introductionmentioning

confidence: 99%

“…A study conducted on Platreef concentrate by Mwase et al (2012) suggests that the reaction between sperrylite and cyanide is not influenced significantly by temperature or reagent concentration, but is most likely a diffusion controlled reaction. It was postulated that some form of passivation may occur at the surface of the mineral in that a small quantity of Pt leaching into solution leaves behind an As layer which passivates the surface of the mineral.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing the leaching of sperrylite (PtAs 2 ) in cyanide-based solutions

Mwase

Petersen

2017

Hydrometallurgy

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The mineral sperrylite (PtAs2), unlike other Pt minerals, has shown to be resistant to cyanide leaching, even at elevated temperatures of 50°C. This has prevented further development of a two-stage heap leaching process, of which the second stage is cyanide leaching for a Platreef ore, due to a considerable portion of the Pt being present as sperrylite.Through a comprehensive set of leaching tests, this study has shown that sperrylite leaches slowly in cyanide due to eventual passivation. The addition of ferricyanide to the cyanide solution results in significantly more Pt being leached (up to 16 times) than with cyanide only under identical process conditions. However, over time passivation occurred in this system also, but can be seemingly be overcome by filtering, rinsing and re-suspending the sperrylite. This was further investigated using a reactor system continuously fed with a ferricyanide-cyanide to leach a fixed bed of sperrylite mineral. Again, gradual passivation of the mineral phase was observed, which was fully reversible following a day of feeding with distilled water. XPS analysis of fresh and leached mineral indicated a depletion of As on the mineral surface, which tallied with an observed preferential leaching of As during leaching, at least initially. As a result, it is postulated that a less cyanide-soluble compound of the form PtAs(X) forms, where x is less than 2. The ease with which the leaching process can be restarted after rinsing the mineral indicates that the adsorption of solution species is the key step in forming a passivating layer. This adsorption is potentially favoured by the gradual surface transformation.Finally, an electrochemical study confirmed that the ferricyanide-cyanide system facilitated an electron transfer reaction at the sperrylite surface with the likely oxidation of As and reduction of the ferricyanide. Gradual passivation of the surface was also observed in this system.

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Copper extraction from low-grade chalcopyrite in a bioleaching column assisted by bioelectrochemical system

Zhang

Huang

et al. 2022

Environ Sci Pollut Res

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Low-grade ores, tailings and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings and solid wastes attracted much attention recently.Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite were achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction e ciency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemicals consumption of acid to improve the copper extraction e ciency need further investigation.

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Assessing a two-stage heap leaching process for Platreef flotation concentrate

Cited by 32 publications

References 26 publications

A novel sequential heap leach process for treating crushed Platreef ore

A novel sequential heap leach process for treating crushed Platreef ore

Characterizing the leaching of sperrylite (PtAs 2 ) in cyanide-based solutions

Copper extraction from low-grade chalcopyrite in a bioleaching column assisted by bioelectrochemical system

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