In the Membrane Engineering lab, the focus is laid on the control and understanding of polymer membrane formation by phase inversion methods, including liquid-induced phase separation (LIPS) process, vapor-induced phase separation (VIPS) process, and dry cast process. The number one goal is definitely to acquire in deep knowledge in order to fully control morphologies of polymer membranes. By discriminating important parameters, membranes’ arising properties can be tuned as well.
One major concern, common to several on-going studies, is the formation of anti-biofouling membranes. Specifically, we aim at applying our membranes in water treatment modules and blood filtration devices. In waters, biofouling of membranes is mainly owed to the adhesion of proteins and attachment of bacteria. On the other hand, membranes for blood filtration must be hemocompatible, that is, prevent the adsorption of proteins that would lead to undesired biological responses such as blood clotting. The approach is the same in both cases. Several methods are being investigated using hydrophobic polymers that offer outstanding bulk properties, and various types of amphiphilic polymer additives providing the hydrophilic interface required. Among these techniques, a special attention is given to the blending method coupled to a phase separation process, since it allows preparing low-biofouling membranes in one single unit operation. We work on the development of flat sheet membranes as well as on the design of hollow-fibers.
Recently, we have started to lay the focus on the development of membranes for oil/water separation. Indeed, many industries produce oily wastes directly discharged in the environment. This problem has to be addressed. According to recent reports, tuning the membranes’ surface properties should allow separating efficiently oil from water in emulsified wastes. Therefore, we work on the design by phase separation processes of superhydrophobic/superoleophilic membranes as well as we intend to develop superhydrophilic/superoleophobic membranes. If fair mechanical properties along with desired surface properties are reached, these novel membranes should eventually lead to an efficient separation of oil from water. Further, the process is expected to be cost- and energy-efficient, since a solely gravity-driven process is expected.
In our lab, we use several glove boxes to prepare membranes by VIPS, in which temperature is controlled, as well as relative humidity (from 20% to 100%). Dry cast process is achieved making use of ovens. Characterization of membrane is mainly performed at the Research and Development Center for Membrane Technology, outside the Engineering Building in which our lab is located. We use scanning electron microscope (SEM) and atomic force microscope (AFM) to characterize the structures. Porosity is assessed by nitrogen adsorption/desorption method. For surface chemical composition, FT-IR and x-ray photoelectron spectroscopy (XPS) tests, as well as X-ray diffraction (XRD) measurements for semi-crystalline and crystalline polymer membranes, are carried out. Mechanical properties of polymer membranes are evaluated performing tensile tests. Water contact angle, hydration capacity, protein adsorption, bacterial attachment and blood compatibility experiments are performed in collaboration with the Biomaterials and Biomolecular Engineering lab (Professor Chang). As for the filtration experiments, dead-end filtration tests are usually first carried out so as to have an idea of low-biofouling properties, followed by cross-flow filtration when preliminary tests end up with promising results.