Fabrication of polyethersulfone hollow fibers for ultrafiltration


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Chemical Engineering, Turkey

Approval Date: 2014

Student: GÜLÇİN KALTALI

Co-Supervisor: PINAR ZEYNEP ÇULFAZ EMECEN, HALİL KALIPÇILAR

Abstract:

Hollow fiber membranes take an important part in membrane separation processes. They are used in many areas like gas separation, pervaporation, ultrafiltration and microfiltration processes due to their advantages like high membrane area per volume and easy backwashability. Poly(ethersulfone) (PES) is one of the most commonly used polymers in preparing hollow fiber ultrafiltration membranes. Due to its hydrophobic character, use of hydrophilic additives is usually necessary to make membranes resistant to fouling. In this study, poly(ethylene oxide) PEO based additives (Pluronic F-127, PEG 10k and Triton X100) were used for preparing PES based hollow fiber membranes. It was observed that adding water to polymer dope delays macrovoid formation in the hollow fibers. Pure water permeance of membranes decreased by adding water to polymer dope and all membranes retention values for bovine serum albumin (BSA, 66 kDa) were above 90%. By using water in polymer dope together with 50 0C coagulation bath, pore sizes became larger and prepared membranes were nearly in microfiltration range. The stability of the additives in the membrane matrix was examined via FTIR to estimate the anti-fouling performance of membranes in long-term. According to ratio of characteristic peak intensities of additives and PES; it was observed that all additives remained in the membrane matrix after coagulation. Fouling characterizations were done by dead-end constant flux filtrations of BSA with intermediate backwashing. Among tight ultrafiltration membranes, Triton X100 showed lowest fouling resistances among additives. After Triton X100 additive, Pluronic F-127 showed second lowest fouling results. It was found that reversibility of fouling was highest in membranes with Pluronic F-127 additive. In loose ultrafiltration group; membrane with Pluronic F-127 additive showed the best fouling characteristics. Between these three additives; Pluronic F-127 and Triton X100 additives can be more preferable in use than PEG 10k additive according to their stability and better anti-fouling properties.