Non-toxic leaching and recovery of gold using thiosulfate based lixviant and Selmext metal separation technology


Karin Löfstrand




Purpose and goal

The project proposes a new concept for leaching and extraction of gold from mineral concentrates and waste streams by replacing todays cyanide leaching with a non-toxic and economical thiosulphate and Selmext process. The goal is to design, build and operate a pilot system to leach mining materials, separate copper from gold and extract the gold. Chromaforas method solves the main problems related to thiosulfate leaching, ie. control of degradation of lixiviant liquid and recovery of gold from the solution. In addition, all chemical reagents in the process can potentially be reused.

Expected results and effects

Chromafora´s concept provides a more efficient process control and uses more environmentally friendly reagents which enables a circular, environmentally friendly, and non-toxic gold leaching of ore and mining waste. This makes gold leaching more accessible to the entire mining industry but mostly benefits small to medium sized actors looking for an alternative to cyanide leaching whether the reason being, environmental, regulatory, social or permit related. Local leaching and gold mining can increase production and save emissions from transportation to remote refineries.

Planned approach and implementation

Chromafora is the project coordinator and will plan and build a pilot plant based on previously established parameters in the laboratory. The pilot plant will have a capacity of 1000 kg of material (approx. 100g of gold) per day. The pilot trials will be carried out at the project partner Björkdalsgruvan. Björkdalsgruvans participates by supplying materials and a suitable location. In parallel with the pilot design, the Dep of Civil, Environ and Nat Res Engin at Luleå University of Technology will contribute with research to further improve process parameters and recycle reagents.