Hydrophobic polyethersulfone porous membranes for membrane distillation

Abstract

Membrane distillation (MD) is a thermal, vapor-driven transportation process through micro porous hydrophobic membranes that is increasingly being applied to seawater and brine desalination processes. Two types of hydrophobic microporous polyethersulfone flat sheet membranes, namely, annealed polyethersulfone and a polyethersulfone/tetraethoxysilane (PES/TEOS) blend were prepared by a phase inversion process. The membranes were characterized and their performances were investigated using the vacuum membrane distillation of an aqueous NaCl solution. The performances of the prepared membranes were also compared with two commercially available hydrophobic membranes, polytetrafluorethylene and polyvinylidene fluoride. The influence of operational parameters such as feed temperature (25-65°C), permeate vacuum pressure (200-800 mbar), feed flow rate (8-22 mL/s) and feed salt concentration (3000 to 35000 mg/L) on the MD permeation flux were investigated for the four membranes. The hydrophobic PES/TEOS membrane had the highest salt rejection (99.7%) and permeate flux (86 kg/(m 2 $h)) at 65°C, with a feed of 7000 ppm and a pressure of 200 mbar.

Engineering hydrophobic surface on polyethersulfone membrane with bio‐inspired coating for desalination with direct contact membrane distillation

“…It should be noted that this flux reduction in the DCMD system has a lower gradient than in other membrane systems, such as RO; hence increase in salt concentration has a lower negative effect on the Flux in DCMD 55 . Additionally, the reduction can be attributed to the effect of temperature and concentration polarization, which increased the thickness of the boundary layer and consequently reduced the evaporation driving force 46 . As the feed's salt concentration increased, the rejection rate stayed constant at almost 99.7% from 2 to 5 wt% but decreased to 99.4% when the salt concentration was 7 wt%.…”

“…55 Additionally, the reduction can be attributed to the effect of temperature and concentration polarization, which increased the thickness of the boundary layer and consequently reduced the evaporation driving force. 46 As the feed's salt concentration increased, the rejection rate stayed constant at almost 99.7% from 2 to 5 wt% but decreased to 99.4% when the salt concentration was 7 wt%.…”

“…In 2013, Khayet 44 and Qtaishat et al 45 fabricated various membranes with PES and surface macromolecules (SMMs) for radioactive waste treatment and desalination by DCMD, respectively. Abdallah et al 46 made two membranes, PES and PES/TEOS, and discussed them in a VMD desalination process. Their work's results were compared with those of two commercial hydrophobic PTFE and PVDF membranes and showed promising and better performance.…”

“…The porous sponge-like structure of these membranes' cross-sections also prevailed on their surfaces. High surface porosity positively affects flux in DCMD because it increases the effective surface area for water evaporation 46,51.…”

Preparation and characterization of different geometrical shapes of multi-bore hollow fiber membranes and application in vacuum membrane distillation

“…The MBHF structure provides an improved mechanical strength required for different applications and development the membrane performance. Moreover, the MBHF membrane has high stability and durability compared with the conventional single-bore hollow fiber (Abdallah et al 2015;El-Zanati and Abdallah 2015;Haase et al 2017). The single-bore hollow fibers break and entangle during continuous operations, but the new generation of hollow fiber membranes of multi-bore configuration shows remarkable improvement.…”