Integrated Membrane Process Coupled with Metal Sulfide Precipitation to Recover Zinc and Cyanide

Gabriel Seriche,Humberto Estay,René Ruby-Figueroa,Michelle Quilaqueo,Elizabeth Troncoso,Ignacio Cortés,Minghai Gim-Krumm,Lorena Barros

doi:10.3390/min12020229

Gabriel Seriche, Humberto Estay + Show 6 more

Open Access

https://doi.org/10.3390/min12020229

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Abstract

In gold cyanidation plants, which include a zinc cementation process, there is a progressive increase in zinc content in the solution and a higher cyanide concentration in leaching tailings. Consequently, there are opportunities to: (i) recover zinc and cyanide from these solutions, (ii) generate a saleable ZnS by-product, and (iii) reduce cyanide consumption and cyanide concentration in leaching tailings. Previous studies have proposed the use of the SART (Sulfidization, Acidification, Recycling, and Thickening) process for this purpose; however, this process has disadvantages that must be addressed. This study presents the results of the experimental assessment of an alternative process, the SuCy process, which uses an integrated membrane process. The SuCy process is composed of a metal sulfide precipitation coupled with a membrane filtration stage, a membrane contactor step to recover and concentrate cyanide, and a final neutralization and ultrafiltration stage. The flux obtained for zinc sulfide separation was around 0.01 L/m2s, with cyanide recovery of 95% at 60 min, whereas flux for ultrafiltration was 0.22 L/m2s. A comparison with an experimental study of the SART process at laboratory scale showed that the SuCy process could obtain a higher zinc recovery and can reduce the solid–liquid separation equipment by around five times. Therefore, the SuCy process could be a promising alternative for zinc and cyanide recovery in gold cyanidation.

Highlights

The conventional method to extract gold and/or silver from ores, tailings, or wastes is cyanidation
This study presents the first assessment of the integrated membrane process (The SuCy process) at laboratory scale, targeting cyanide solutions containing zinc
The particle size distribution (PSD) shows that 91% of particles were smaller than 10 μm, and 17% were even below 1 μm

Summary

Introduction

The conventional method to extract gold and/or silver from ores, tailings, or wastes is cyanidation. In gold plants with MC process, the zinc concentration increases progressively because the unique zinc output of the system is the leaching tailings, promoting a build-up of zinc in the cyanidation plant and the rise of cyanide concentration in solutions and leaching tailings In this regard, there are studies proposing the use of the SART (Sulfidization, Acidification, Recycling and Thickening) process to recover zinc and cyanide, as an opportunity to produce a saleable by-product and to reduce cyanide consumption, respectively [2,3,4,5]. ZnS precipitate presents colloidal behavior and low settling rates, affecting the solid–liquid separation stage [8] In the latter, the option to assess different methods to perform the solid–liquid separation more efficiently could be needed to deal with these complex precipitates

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