In order to remove treatment liquid (21) from a planar material to be treated (10), which is transported in an assembly for the electrolytic or wet-chemical treatment of the material to be treated (10), or to promote the exchange of material on the surface of the material to be treated (10), a roll with a roll surface (4, 14) is provided. The roll surface (4, 14) is arranged relative to a transport path of the material to be treated (10) so that a gap (8, 18) remains between the roll surface (4, 14) and a useful region of the material to be treated (10) opposing the roll surface (4, 14), which extends over the useful region. The roll is driven rotatably so that at the gap (8, 18) a relative speed is produced between the roll surface (4, 14) and the material to be treated (10).