Characterization, performance analysis and comparison of ZrO2 or TiO2 doped Al2O3 composite membranes using sol-gel technique

Growing studies that show that composite materials can improve performance by making up for the defects of ceramic membranes made of a single material. This paper prepared ZrO2/Al2O3 and TiO2/Al2O3 composite coating sols using the sol-gel technique. Ceramic membranes were prepared by dip-coating process and calcined at 350 degrees C calcination. The physical-chemical properties of membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N2 adsorption-desorption measurements and scanning electron microscopy (SEM). The permeability and separation performance of membranes were analyzed by doping amount, dye type and pressure difference as reference factors, and the removal rates of chemical oxygen demand (COD) and chroma in the experiment were compared. These results showed that the modified composite membranes had better microstructure, and their retention rates on the dye solutes were significantly enhanced. When the Zr/Al and Ti/Al molar ratio (nZr, nTi) of the composite membrane is 0.5, under the experimental conditions of 0.2 MPa pressure difference and 30 min filtration time, the membrane rejection rates of the four 50 mg/L dyes reached more than 80%, which was much higher than that of the Al2O3 membrane of 57.9%. At the same time, the removal rates of COD and chroma were also greatly improved. The results revealed that the use of composite materials would be required to further explore their potential to improve the performance of ceramic membranes.