Integrated membrane process coupled with metal sulfide precipitation to recover zinc and cyanide

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/m(2)s, with cyanide recovery of 95% at 60 min, whereas flux for ultrafiltration was 0.22 L/m(2)s. 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.