An arrangement for the dry reconditioning of used foundry sands in which used sand is fluidized with air or an air/gas mixture and flung against a precipitator to separate and remove substances covering sand particles. The precipitator has several planar baffle elements arranged in concentric circles around a conical deflector. A jet of used sand/air directed toward the deflector expands radially outwardly toward the baffle elements so that the jet is decelerated several times by the deflector and the baffle elements and, in a confined space, split into individual streams and swirled to provide heavy mechanical friction between sand particles and between sand particles and the baffle elements.