Sonication-Enhanced In Situ Assembly Of Organic/Inorganic Hybrid Membranes And Their Separation Performance

Organic/inorganic hybrid membranes show high thermal stability, mechanical strength and special chemical properties by combining the advantages of bothorganic and inorganic components. The development of organic/inorganic hybrid membranes is one of the most important promising directions of separation membrane in the future. However, to overcome the aggregation of inorganic particles within the polymer matrix and realize the nanoscale dispersion is one of the major bottlenecks in the process organic/inorganic hybrid membrane preparation.In this paper, dihydroxypolydimethylsiloxane(PDMS) hybrid membrane was prepared onto polysulfone supporting membrane.(PS). In situ sonication assembly iwas used to improve the nanoscale dispersion of particles within hybrid membrane and the comprehensive performance. The surface morphology was revealed by scanning electron microscopy(SEM). The results showed that the nanoparticles were well dispersed within the polymeric matrix and were strongly integrated with PDMS. X-ray energy dispersive analysis(EDX) linear scanning element analysis combined with SEM figure suggested that the thickness of the organic/inorganic selective layer was ~6 μm. Surface roughness of the membranes was characterized by AFM, the results show that secondary aggregation of the nanoparticles was effectively avoided and the roughness was thus reduced. The measurmentes of the contact angle CAs of water and ethanol on the membranes suggested that the hydrophobic of surface was improved due to the hierarchical structured by ultrasonic cavitation, and the hybrid membrane had the highest affinity to ethanol when the silica loading was 5 wt%.In this paper, the hybrid membranes produced by in situ sonication assembly were used in pervaporation and organic solvent nanofiltration. The effects of ultrasonic cavitation, loading rate, number of dipping cycles, feed ethanol concentration, temperature of feed solution and ultrasonic power on the membrane performance were invesitgated. Especially, these phenomena are analyzed from the micro level. The appropriate condiditions were selected as: 5wt% silica loading, 3 sonication-enhanced in situ assembly cycles, 300 W ultrasonic power, for 5 wt% ethanol/water system at 60℃. Under these given conditions, the separation factor could reach 12.5 while the permeate flux was 807 g/m2·h. In the nanofiltration of 100mg/L methyl blue, the rejection and a flux could reach over 99% and 91 L/m2·h·MPa, respectively(operation pressure: 0.4MPa). During organic solvent nanofiltration process, the membrane may be swollen by organic solvent, so the stability was very important in the process of actual operation. Membranes stability were investigated in this paper, the continuous 80 h operation results suggested that the rejection and the flux could still maintained more than 90% and 70L/m2·h·MPa, respectively. Morover, the assembly process and performance of PDMS/ZIF-8 and PDMS/ZSM-5 produced by in situ sonication assembly were also studied.