High-performance ultrafiltration mixed-matrix membranes based on cellulose acetate and nanohydroxyapatite

The asymmetric cellulose acetate mixed-matrix membrane (MMM) filled with nanohydroxyapatite was prepared by a modified phase inversion method. To prevent the agglomeration of the hydroxyapatite nanocrystals and to obtain ultrafiltration composite membranes, a surfactant (12-hydroxystearic acid) was used. The hydroxyapatite nanopowder was dispersed in acetone-dissolved 12-hydroxystearic acid and then mixed homogeneously with acetone-dissolved cellulose acetate (CA). The process of addition of hydroxyapatite nanosuspension to CA solution resulted in asymmetric composite membranes with higher pure water flux and superior NaCl rejection in comparison to the CA membrane. The best performing composite membrane, the CHM-30 sample, shows a retention of 99.1% and a high water permeability of 34.96 L/m2 h bar. The results showed that the nanohydroxyapatite—cellulose acetate MMMs can be used in ultrafiltration applications.