Metal speciation of historic and new copper mine tailings from Repparfjorden, Northern Norway, before and after acid, base and electrodialytic extraction

In Kvalsund, Northern Norway, a permit for submarine mine tailings disposal in Repparfjorden was recently issued for a copper mine with expected operation from 2019. A copper mine was active in the same area in the 1970s and also deposited mine tailings in the fjord. Investigations of the metal binding in the historic and new mine tailings (produced from bedrock in the area) have been undertaken in this study.

Acid and base extraction experiments provided desorption curves of mine tailing suspensions as a function of pH (0.5-12.7), and showed that Cu was more easily desorbed in the historic mine tailings. Substantial desorption (>40%) for both historic and new mine tailings occurred at pH values below 3 and above 12.

These results combined with metal speciation, showing that the binding of Cu in the sediment changes around pH values 3 and 10, indicate potential for extraction of more Cu from the new mine tailings. Electrodialysis, based on applying an electric field of low intensity to extract metals from polluted soils/sediments, was designed for acidic and alkaline extraction, and in both cases more Cu was extracted than in the pure acid/base extractions, while maintaining low mobilisation of other metals.

Electrodialysis can hence be designed to target extraction of Cu while limiting the mobilisation of other metals.