The Study On The Method Of Ultrafiltration Membrane Characterization Based On Scanning Probe Microscopy

Ultrafiltration separation,as a typical technology of membrane separation, has wide applications in fields such as environmental protection, medical treatment, food industry, wastewater treatment, et al. Ultrafiltration membrane is the key device in ultrafiltration separation techniques. The characterization technologies for surface topography and antifouling property of ultrafiltration membrane are key factors of the separation efficiency and the service life. Based on the practical application requirements, the paper researches the theory and method of characterization technologies for surface topography and antifouling property using the scanning probe microscopy(SPM) in vacuum and atmospheric environment. Some novel ideas and methods are proposed to solve the problems in the traditional characterization technologies of ultrafiltration membrane. The above methods have important guiding significance for the research and production of ultrafiltration membranes. The main contents and innovations of the thesis are listed as follows.1. The theory and method of the characterization technologies of ultrafiltration membrane were researched. Based on the ultra high vacuum scanning tunneling microscopy(UHV-STM), characterization method of ultrafiltration membrane surface topography was proposed. Based on the atomic force microscope in atmospheric environment, characterization method of ultrafiltration membrane antifouling property was proposed. According to the experimental results, the factors influencing antifouling property were analyzed and contrasted.2. A system of UHV-STM was developed. The tunneling current extraction circuit and feedback circuit were designed with better sampling precision and better accuracy of the scanning image of the surface topography. The mechanical parts of the measuring head, the sample holder and the spring-damping isolation system were set up. The software consisting of real-time data acquisition and image processing was developed. The UHV-STM was used to characterize the surface topography of the ultrafiltration membranes. The method using UHV-STM to characterize the surface topography of the ultrafiltration membranes was validated by the experiments.3. As the spring constant calibration of the AFM cantilever probe was implemented with a precision balance calibration system, the AFM force curve method was used to measure the adhesion force between the protein-immobilized tip and the ultrafiltration membrane. The comparison of adhesion force measured with different probes and membranes was used to estimate the effects of adhesion as one of various impact factors of membrane antifouling property. Consequently, force volume mode of a novel commercial AFM was also used to realize the 2D in-plane scanning of the adhesion force information in the ultrafiltration membrane antifouling characterization.4. The theoretical model between the change of resonant frequency of AFM tip and the interaction force was established. The method based on ultrasonic AFM(UAFM) measurement system was proposed to measure the interaction force and get the surface topography of the ultrafiltration membranes at the same time. The method based on Electric force microscopy(EFM) was proposed to measure the interaction force, measure the elastic modulus and get the surface topography of the ultrafiltration membranes at the same time. These methods were valuable reference for the relationship research between several factors of antifouling property, and for the development and application of the ultrafiltration membranes.5. The characterization method based on the combination of AFM and STM was proposed to measure the Electronic distribution, measure the elastic modulus and get the surface topography of the sample at the same time. External power source and tunneling current exaction circuits was applied between the probe and the sample for upgrading and renovation of EFM mode in AFM. The novel scanning mode combining AFM and STM was applicable for the simultaneous imaging of surface topography, elastic modulus and surface electron state distribution measurement of the sample.