In this work the preparation of cobalt spinel CoAl2O4 is described. The technique of colloidal solution destabilization was used as the sol-gel process. The powder obtained from the dried gel was characterized by thermal analysis (thermogravimetric and differential), X-ray diffraction, infrared spectroscopy, and specific surface area measurement. Crystallization of CoAl2O4 spinels occurs at about 400 degreesC. The study of surface properties (surface charge and electrophoretic mobility) of the spinel powder fired at 600 degreesC, in suspension in different electrolyte solutions (10(-3) molar ionic strength), shows that the spinel material charge depends on the pH of the solution. The spinel sol was used for the preparation of membrane by the slip-casting method.