Process Implications of Ferrolysis in Hyper-Saline Water

Iluka Resources Ltd developed the Jacinth-Ambrosia Mine (Jacinth) in the Eucla Basin during 2009 and 2010. In this arid climate the operation relies on hyper-saline groundwater from a palaeochannel for process and potable water supplies. The water is hyper-saline, acidic and mildly reducing, with high ferrous iron concentrations. Ferrolysis commences on exposure of water to oxygen, resulting in increased acidity and the conversion of dissolved ferrous iron to insoluble ferrihydrite. The unstable groundwater forces a careful balance between interventions relating to maintaining pipeline efficiency, corrosion protection and processing aspects. Providing an oxidising environment at the head of the pipeline will result in the precipitation of akaganenite and goethite in the pipeline, which over time reduces pipeline efficiency. However, sending too much ferrous iron forward may reduce processing performance.The processing plant experiences changes in water chemistry in response to the variability of iron concentrations and pH within the pipeline, and the spatial and chemical variability of ore. As the main orebody at Jacinth contains little buffering capacity a source of carbonate in the overburden is carefully used to allow the cost-effective control of process water pH.This paper highlights the importance of understanding the chemistry of saline make-up water, ore, and overburden when designing water treatment facilities and heavy mineral processing facilities.