The Study On The Method Of Investigating The Oil Antifouling Of Membranes In Aqueous Solutions Based On Atomic Force Microscope

Ultrafiltration membrane is the most effective way to deal with oily wastewater,and the essence of oil/water separation is the interface interactions.The surface resistance to oil has a direct impact on filtration efficiency,film cleaning and life span of ultrafiltration membranes.Nowadays,the atomic force microscope(AFM)has provided unprecedented opportunities to study interface interactions.Based on the practical application requirements,the paper researches the techniques of characterization technologies for surface topography and antifouling property utilizing the atomic force microscope(AFM)in fluid.The main work of this paper is listed as follows.1.Traditional oil-water separation technologies was introduced and membrane separation technology focusing on the preparation theory of films,common manufacturing methods,separation principle,pollutants and pollution mechanism of membranes and membrane characterization techniques was also decribed.The status and limitations of the present characterization techniques were analyzed,and the significance of this research was pointed out.2.A system of AFM and its working principle,force curve testing technology,calibration methods of cantilevers were described and a novel idea was proposed.Namely,the antifouling performance of membranes was compared by measuring the adhesion forces between the AFM probe with an oil droplet immobilized and the membrane surface.The details of this idea were presented.3.Probe modification was researched and the preparation method of oil droplets,as well as the proper type of oil and probe for force curve measurement,was discussed.The experiments showed that oil droplets attached on the probe were stable and that the cantilever could be repositioned and used to adhesion force measurement.Through a large number of repeated experiments,the oil(hexadecane)and NP-O10 probes were selected to achieve adhesion measurement.4.By changing the approaching and retracting speed of the probe,the interactions between the probe and surface of silicon and the membrane were preliminarily explored,and the related experimental phenomena was analyzed.It was found that the speed of extending/retracting on AFM force curve measurement had a great influence on the results of the experiment in fluid.It provided important reference for follow-up experiments.5.The adhesion forces between the AFM probe with an oil droplet immobilized and a serial of membrane surfaces in aqueous solutions were evaluated utilizing force curves,which reflected the influence of the additive F127 on the antifouling property of UF membranes.The data of contact angle measurement and filtration experiments agreed with AFM force curves very well,which could be an evidence of correctness and effectiveness of AFM force curve method.And the results were consistent with the theoretical design of the modification of ultrafiltration membranes.6.The effect of charge and surfactant on the interaction between oil droplets and the charged membranes was explored,and a noval method of modificating the AFM probe by oil was proposed.