The present invention relates to a process for separating at least one first material from a mixture comprising this at least one first material, at least one second material and magnetic particles, which comprises the following steps (A) at least partial removal of the magnetic particles by application of a magnetic field gradient, optionally in the presence of at least one dispersing medium, to give a mixture comprising at least one first material and at least one second material and a reduced amount of magnetic particles, (B) contacting of the mixture comprising at least one first material and at least one second material from step (A) with magnetic particles so that the at least one first material and the magnetic particles agglomerate, (C) separation of the agglomeration product from the mixture from step (B) by application of a magnetic field gradient and (D) dissociation of the agglomeration product separated off in step (C) in order to obtain the at least one first material and the magnetic particles separately, and also a control and/or regulation device for a corresponding apparatus.