Interfacial characteristics in membrane filtration for oil-in-water treatment processes

Abstract

Membrane filtration is an effective method for the separation of O/W emulsion wastewater. However, the membrane fouling of this technique restricts its wide application. Up to now, the understanding of the membrane fouling mechanism is still insufficient. Previous scholars have stated that the membrane filtration for oil-in-water treatment processes is essentially interfacial problem. Therefore, studies on the interfacial effects in the process of oil-water membrane filtration is crucial for elucidating the fouling mechanism. In this paper, one novel device with oil-water-membrane system was designed. This device has the function of studying the interfacial characteristics under pressure water condition (ICPW). Static adhesion and hydrodynamic interfacial characteristics of oil droplet on membrane surface were studied with image analysis method. The results showed that surface wettability is the internal factor, trans-membrane pressure (TMP) and cross flow are external factors, which determine whether oil droplets can penetrate into membrane pores. In the condition of static water, the oil droplet either penetrates freely through the oleophilic membrane, or adheres on the oleophobic membrane surface with static contact angle. However, in the flowing water, due to the influences of TMP and cross flow rate, the motion and deformation of the oil droplets can be divided into three patterns: penetration, oscillation and mixed flow. The former two patterns correspond to membrane fouling forms as pore blocking, bridging or plugging, respectively, depending on the interfacial effect. Furthermore, theoretical models were established to analyze the hydrodynamic interfacial characteristics of oil droplet.