The possibility of applying vacuum membrane distillation for drying polystyrene microparticles was recently confirmed and the best membrane unit design, named Vacuum Membrane Dryer (VMDr), identified. However, some limits in the production efficiency were underlined. Therefore, in the present work, further investigations to improve the performance of the previously developed and selected unit were carried out. In particular, the effect of mixing and air bubbling was analyzed. Moreover, the efficiency of the VMDr as function of the particles size, the membrane area and the membrane properties was studied. (C) 2015 Elsevier B.V. All rights reserved.