Institute of Geology of Karelian Research Centre of RAS (Petrozavodsk, Russia):

Rozhkova V. S., Junior Researcher, e-mail: vrozhk@krc.karelia.ru

Kovalevskiy V. V., Head of Laboratory, Doctor of Geological and Mineralogical Sciences

Kochneva I. V., Leading Engineer-Technologist

Institute of Northern Water Problems of Karelian Research Centre of RAS (Petrozavodsk, Russia):

Lozovik P. A., Head of Laboratory, Doctor of Chemical Sciences

An in-depth study of leaching phenomena of different shungite rock samples in water is carried out. The study with using the up-to-date methods and instruments reveals that all investigated aqueous extracts of shungite rocks differ in ionic and microcomponent composition. Leaching of different genesis shungite rocks depends not only on the composition but also on the pH value. Hydrolysis rates of minerals (particularly sulfides), increase in acidic medium, what leads to a high content of heavy metals (Ni, Cu, Fe, Cd, Pb) in solutions. On the other hand, leaching of some elements (Na, Ca) is independent on the acidification. Aqueous extracts of different shungite rocks are notable for concentrations of some elements. It should be noted that no common correlation is found between element contents in shungite rocks and those in aqueous extracts. For example, the aluminium oxide content differs from 4,6 to 7,6 wt.% in different samples. Aluminium concentration in the aqueous extracts differs from 17960 to 20 ppb respectively. So, the largest aluminium concentration is remarkable for the sample with smallest aluminium oxide content. There is determined an overrunning of maximum allowable concentrations of some dissolved substances, including heavy metals. On the basis of this, a water conditioning application of shungite rocks may be restricted. Choice of a shungite rock and water conditioning process should be taken into account.

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