A process for separating at least one first material from a mixture comprising this at least one first material and at least one second material, which comprises at least the following steps: contacting of the mixture comprising at least one first material and at least one second material with at least one magnetic particle in the presence of at least one dispersion medium, so that the at least one first material and the magnetic particle aggregate, if appropriate, addition of further dispersion medium to the dispersion obtained in step, separation of the aggregate of at least one first material and at least one magnetic particle from the dispersion from step or in an apparatus which in its interior has a separation space having at least one magnetizable device, preferably in the longitudinal direction, by application of an external magnetic field which is generated outside the separation space of the apparatus, so that the aggregate adheres to the magnetizable device and the second material which does not adhere to the magnetizable device is discharged with the dispersion which is in motion, flushing and/or blowing-out of the separation space of step while the external magnetic field is applied in order to be able to carry out a low-contamination change of the dispersion medium, removal of the aggregate from the magnetizable device by removal of the magnetic field and flushing with a second or modified dispersion medium in which the aggregate is dissociated in order to obtain a dispersion which comprises the at least one first material and the at least one magnetic particle separately from one another, treatment of the dispersion from step in an apparatus which in its interior has a separation space having at least one magnetizable device, preferably in the longitudinal direction, by application of an external magnetic field which is generated outside the separation space of the apparatus, so that the at least one magnetic particle adheres to the magnetizable devices and the at least one first material remains in dispersion, flushing and/or blowing-out of the separation space of step while an external magnetic field is applied in order to be able to carry out a low-contamination change of the dispersion medium, removal of the at least one magnetic particle from the magnetizable device by removal of the magnetic field. contacting of the mixture comprising at least one first material and at least one second material with at least one magnetic particle in the presence of at least one dispersion medium, so that the at least one first material and the magnetic particle aggregate, if appropriate, addition of further dispersion medium to the dispersion obtained in step, separation of the aggregate of at least one first material and at least one magnetic particle from the dispersion from step or in an apparatus which in its interior has a separation space having at least one magnetizable device, preferably in the longitudinal direction, by application of an external magnetic field which is generated outside the separation space of the apparatus, so that the aggregate adheres to the magnetizable device and the second material which does not adhere to the magnetizable device is discharged with the dispersion which is in motion, flushing and/or blowing-out of the separation space of step while the external magnetic field is applied in order to be able to carry out a low-contamination change of the dispersion medium, removal of the aggregate from the magnetizable device by removal of the magnetic field and flushing with a second or modified dispersion medium in which the aggregate is dissociated in order to obtain a dispersion which comprises the at least one first material and the at least one magnetic particle separately from one another, treatment of the dispersion from step in an apparatus which in its interior has a separation space having at least one magnetizable device, preferably in the longitudinal direction, by application of an external magnetic field which is generated outside the separation space of the apparatus, so that the at least one magnetic particle adheres to the magnetizable devices and the at least one first material remains in dispersion, flushing and/or blowing-out of the separation space of step while an external magnetic field is applied in order to be able to carry out a low-contamination change of the dispersion medium, removal of the at least one magnetic particle from the magnetizable device by removal of the magnetic field.