Nanocomposite membranes for osmotic processes: Incorporation of functionalized hydroxyapatite in porous substrate and in selective layer

Development of new membrane materials for osmotic processes is an important field for increasing the efficiency of the technology. In this work, hydroxyapatite particles (Hapf) functionalized by plasma treatment were added to a porous cellulose acetate substrate and to a selective polyamide layer of nanocomposite membranes to evaluate its performance in osmotic processes. Contact angle, scanning electron microscopy, FT-IR, zeta potential and atomic force microscopy were performed to characterize nanocomposite membranes. Hapf incorporation in the porous CA substrate improved the water flux in forward osmosis from 13.8 to 18.0 L.h(-1).m(-2) which was related to the augmented hydrophilicity and lower diffusion resistance of the substrate. The addition of particles in the selective layer allowed a further increase up to 22.6 l.h(-1)m(-2), without affecting the reverse salt flux. For reverse osmosis, water permeability increased from 0.83 to 1.41 L.h(-1)m(-2).bar(-1), maintaining high rejection for NaCl and MgSO4, when particles were incorporated into the selective layer. Composite membranes with CA porous substrate and PA selective layer exhibited promising properties for forward osmosis, and the incorporation of novel functionalized Hapf in both layers allowed for a further adjustment of the membrane hydrophilicity and indicates an advance in membrane material technology.