Hybrid Integral Asymmetric Cellulose Acetate/Silicon Dioxide Ultrafiltration Membranes for Uremic Blood Purification

Monophasic hybrid cellulose acetate/silica (CASiO₂) integrally skinned membranes with silica contents between 5–18 wt.% were synthetized by an innovative method which combines the phase inversion and sol-gel techniques. The morphological and topographical characterization was performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Permeation experiments were performed to determine the hydraulic permeability and rejection coefficients to reference solutes pertaining to the metabolic functions of the kidney. SEM confirmed asymmetric membrane cross-section structures and AFM showed that the introduction of silica reduced the submicron surface roughness at least 3 times compared to the pure CA membrane reaching a roughness mean value below 2.5 nm. Permeation studies show that the integration of silica into CA membranes increased hydraulic permeability of the hybrid CASiO₂ membranes by a factor of ~2 and that all of the hybrid membranes fully permeate urea and totally reject albumin. In terms of hemocompatibility, all of the CASiO₂ membranes are non-hemolytic, low thrombogenic and do note promote the highest stages of platelet activation.