The invention relates to technical conditions of composition and use applied to the existing method and device for extracting heavy metals from an aqueous solution with a high salt concentration, with the single aim of adapting said method to technical, technological and ecological developments that have taken place since the protection thereof, and substantially optimising the results. To this end, the invention of the present patent application adds, to the device of the initial patent, an electronic control means (MC) that can manage three new actions. Disclosed are also modifications in the quality, function, destination and operation of certain elements of the device as well as the addition of a filter at the end of the electroplating operation, the purpose of which is to optimise the quality of the rejected effluent.