The impact of physico-chemical parameters on solid-liquid separation of a micronized lactose-in-ethanol suspension is investigated by means of Fraunhofer diffraction, focused beam reflectance measurement (FBRM), electrokinetic sonic amplitude (ESA), sedimentation and filtration experiments. Lactose-in-ethanol dispersions are quite unstable, with a strong particle agglomeration and sedimentation tendency. Only diluted suspensions show a significant impact of physico-chemical parameters such as pH. ESA titrations show the surface properties of lactose to change strongly when acids and bases are added. High base concentrations were found to accelerate cake filtration, while high acid concentrations slow it down.