Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

Abstract

a b s t r a c tThe mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) 1500 as non-solvent additive was introduced to fabricate hydrophobic hollow fiber membrane of polyvinylidene fluoride (PVDF) by phase inversion process, using N,N-dimethylacetamide (DMAc) as solvent and tap water as the coagulation medium. Compared with other three membranes from PVDF/DMAc, PVDF/DMAc/LiCl and PVDF/DMAc/PEG 1500 dope solution, it can be observed obviously by scanning electron microscope (SEM) that the membrane spun from PVDF/DMAc/LiCl/PEG 1500 dope had longer finger-like cavities, ultra-thin skins, narrow pore size distribution and porous network sponge-like structure owing to the synergistic effect of LiCl and PEG 1500. Besides, the membrane also exhibited high porosity and good hydrophobicity. During the desalination process of 3.5 wt% sodium chloride solution through direct contact membrane distillation (DCMD), the permeate flux achieved 40.5 kg/m 2 h and the rejection of NaCl maintained 99.99% with the feed solution at 81.8• C and the cold distillate water at 20.0 • C, this performance is comparable or even higher than most of the previous reports. Furthermore, a 200 h continuously desalination experiment showed that the membrane had stable permeate flux and solute rejection, indicating that the as-spun PVDF hollow fiber membrane may be of great potential to be utilized in the DCMD process.

Preparation of PVDF-CTFE hydrophobic membranes for MD application: Effect of LiCl-based mixed additives

“…Consequently, macrovoids were suppressed and the membrane with excellent interconnectivity and porosity can be gained, however at the expense of decline in mechanical strength [19,33,34]. As such, attempts were made to use PEG/LiCl mixed additives for membrane preparation in order to synergize the advantages of both additives [32,35,36]. Nonetheless, as a crucial factor to membrane properties and performance, the PEG/LiCl mass ratio in casting solution has not been investigated systematically and its impacts on the resultant membranes have hardly been reported.…”

Preparation and properties of PVDF composite hollow fiber membranes for desalination through direct contact membrane distillation

“…Compared with conventional separation processes such as evaporation, distillation and reverse osmosis, MD can be operated under relatively low temperature or low pressure with low energy consumption and high productivity [3][4][5]. There have been extensive researches on MD for the past three decades [2] and various configurations have been developed including direct contact membrane distillation (DCMD), air gap membrane distillation (AGMD), sweeping gas membrane distillation (SGMD) and vacuum membrane distillation (VMD) [6]. Up to the present, MD has been applied to water desalination, wastewater reuse, juice concentration and other industrial areas [7][8][9][10][11].…”

Fabrication and performance of PET mesh enhanced cellulose acetate membranes for forward osmosis

“…The fabrication involved in this work was conducted via a phase inversion process that has been reported in earlier works (Hou et al, 2009). Specifically, the polymer solution was spread evenly on the surface of a clean horizontal glass plate using a casting knife at a gate height of 200 μm.…”