PTFE Hollow Fiber Research Articles

Ozonation of dye wastewater by membrane contactor using PVDF and PTFE membranes

This work aimed to study the decolorization of dye wastewater by ozonation membrane contacting process. Three different dyes, i.e., Direct red 23, Acid blue 113 and Reactive red 120 were selected to be used in this work. The effects of operating parameters which were gas and liquid velocity, liquid phase temperature, dye auxiliary reagents were investigated along with the mass transfer study. Membranes used in this work were PVDF and PTFE hollow fiber membranes. The ozone mass transfer performance and long term performance in ozonation by these two different types of membrane were studied. In addition, decolorization performance and kinetic study of ozonation in the batch system with various operating parameters and dye types were investigated. From the results, the ozone mass transfer increased with increasing liquid velocity, liquid phase temperature, and with the presence of Na 2CO 3. On the contrary, the ozone flux was not influenced by gas velocity. PVDF membrane provided higher ozone flux than PTFE, but PTFE membrane gave more stable and higher flux than PVDF for a long operation period. The ozone flux of different types of dye was in the following order: Direct red 23 > Reactive red 120 > Acid blue 113. Conversely, the decolorization performance of Acid blue 113 was higher than those of Direct red 23 and Reactive red 120. Kinetic analysis showed that decolorization of dyes followed the first order kinetics and the rate constants were in the following order: Acid blue 113 > Reactive red 120 > Direct red 23.

Membrane distillation with hydrophobic macrovoid-free PVDF–PTFE hollow fiber membranes

Hydrophobic polyvinylidene fluoride–polytetrafluoroethylene (PVDF–PTFEPVDF–PTFE) hollow fiber membranes for desalination via direct contact membrane distillation (DCMD) are successfully fabricated. The incorporation of PTFE particles ( <1 μm) into the polymeric matrix enhances the hydrophobicity of the membranes, yielding a resultant water contact angle of 103°. FESEM analysis confirms the formation of macrovoid-free hollow fiber membranes with uniform particle distribution at 50 wt.% PTFE loading. All the fabricated membranes exhibit narrow pore size distributions and have relatively small mean pore diameters between 0.116 and 0.308 μm. Hollow fiber membranes spun at higher air gaps result in above 6% improvement in permeate flux because of the reduction in membrane wall thickness and greater surface porosity. The fabricated membranes demonstrate high thermal efficiency ( EE) of above 80% when subjected to a hot feed solution of 80 °C. PVDF–PTFE membranes spun at an air gap of 4 cm and with 50 wt.% particle loading demonstrate an optimal separation performance of 40.4 kg/m 2 h permeation flux as well as ∼99.8% salt rejection at 80 °C. This performance is comparable or even higher than the commercial hydrophobic membranes for DCMD studies.

Effect of operating variables on the flux and selectivity in sweep gas membrane distillation for dilute aqueous isopropanol

Sweep gas membrane distillation was examined as a possible technique for isopropanol (IPA)–water separation using PTFE hollow fiber membrane module. The composition and flux of the permeate were monitored when feed concentration, operating temperature and flow rate were varied. The upper feed concentration tested was 10 wt.% IPA. Within the feed temperature range of about 20–50°C, IPA selectivity of 10–25 was achieved. Since the concentration near the surface on the membrane increased by the selective adsorption of IPA on the hydrophobic membrane, the selectivity increases. The permeate flux and IPA selectivity increase as feed temperature increase. The flux and selectivity increase at higher flow rates is mainly due to the reduced effects of concentration and temperature polarization. The effect of salt addition to the feed mixture was also examined.