Abstract: A process is described for treating spent batteries of any type, comprising essentially the following stages:a) disintegrating the spent batteries in water to a piece size of less than 7 mm followed by stirring in water, then screening to obtain a pulverlent aqueous turbid fraction (underscreen fraction) and a coarse fraction (overscreen fraction);b) stirring the pulverulent aqueous turbid fraction at a pH of between 7 and 8, followed by filtering by which the solids are separated from the aqueous solution, which is fed to water treatment;c) removing mercury both from the coarse fraction of point a) and from the separated solids of point b) in an indirectly heated continuously rotating mercury removal furnace operating in total absence of air and to which calcium hydroxide has been added, to obtain residues essentially free of mercury.