Hollow fiber membrane fouling controls in ultrafiltration system

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The world's water shortage problem becomes increasingly serious. However, most of the current water desalination/ purification technologies are energy intensive. Membrane technology requires less energy when compare d with the conventional thermal methods without the involvement of a phase change to make a separation. The most widely used membranes are polymeric membranes, although there are still some issues and challenges for their applications including the membrane breakage and membrane fouling. In this study, I explored various ways to make hollow fiber membranes with enhanced properties especially anti organic fouling characteristics. In comparison with flat sheet membranes, hollow fiber membranes have the advantage of self supporting and high packing density. First, as even bore HFM was produced with a stronger tensile strength when compared with the traditional single bore HFM. Second, the zwitterion carboxybetaine methacrylate (CBMA), positively charged [2 --(acryloyloxy)ethyl] trimethylammonium chloride (TMA) with a quaternary amine end group and negatively charged 2 carboxyethylacrylate (CAA) with a carboxyl end group were grafted separately to HFM surface via atom transfer radical polymerization (ATRP). Membranes modified with charged polymers showed an improved antifouling property, but not to the same extent as the membrane with the zwitterionic polymers. Third, we investigated the self cleaning property for HFMs under visible light irradiation when NTiO-2-nanoparticles were used to modify HFMs. PSF and PVDF are common polymers for production of membranes. PSF is vulnerable under UV light irradiation and PVDF membrane has more resistance to UV irradiation compared with PSF membrane. NTN is successfully introduced to PSF membrane surface via LDOPA layer and anchored to PVDF membrane surface via polydopamine. PSF membrane and modified layer on PV DF membrane can likely be deteriorated by UV irradiation. Visible light is advisable for the membrane antifouling improvement. The manipulation of HFM structure and the introduction of photocatalysts can resolve the membrane breakage and fouling issues. Membrane performance can be improved by the unique structure design of HFM and the introduction of unique functionalities. Overall, a special designed HFM with unique structure and/or functionality could resolve issues during the membrane filtration process and this type of membrane could lead to the next generation of the high performance membrane.