Interfacial diffusion assisted chemical deposition (ID-CD) for confined surface modification of alumina microfiltration membranes toward high flux and anti-fouling

Surface modification has been widely adopted to regulate the surface properties of ceramic membranes in order to improve their permeability and fouling resistance in water and wastewater treatment. In this work, an interfacial diffusion assisted chemical deposition (ID-CD) strategy was formulated to realize the confined surface modification of ceramic membranes. The process involves the hydrolysis of TEOS precursor and the subsequent deposition of SiO2 nanolayers on the surface of pre-saturated ceramic membranes, followed by a calcination at low temperature. The confined surface modification has successfully demonstrated by the combined analysis of microstructure, chemical composition and mass loading. Through a deliberate control of the deposition process, an ultrathin SiO2 layer was purposely coated on the alumina grains at the membrane surface, rather than the whole membrane body. Compared with the conventional chemical deposition (CCD), where the dry ceramic membranes were straightforwardly immersed into the precursor-containing solution, the ID-CD process was able to reduce the mass loading of SiO2 to about 1/4, and notably increase the permeability of modified ceramic membranes. Significantly, the modified alumina membranes showed an improved flux recovery ratio (FRR) of 93.7% after static adsorption fouling in HA solution, due to the improved hydrophilicity (WCA = 9.7-10.2) and negative charged membrane surface. Under the cross-flow filtration with a HA solution (50 mg/L), the surface modified alumina membranes showed improved antifouling properties with the successful conversion of irreversible fouling dominated (51.61%) in pristine membranes to reversible fouling dominated (59.51%), without changing the fouling mechanism of intermediate pore blocking model. Therefore, we believe that the ID-CD strategy could be extensively adopted for confined surface modification, in order to develop antifouling and high-permeable ceramic membranes.