Tri-bore PVDF hollow fibers with a super-hydrophobic coating for membrane distillation

Abstract

Membranes with good mechanical strength, high vapor flux and outstanding anti-wetting properties are essential for membrane distillation (MD) applications. In this work, porous polyvinylidene fluoride (PVDF) tri-bore hollow fiber membranes with super-hydrophobicity are developed to achieve these desired properties. The tri-bore hollow fiber offers better mechanical strength than the conventional single-bore fiber. To improve its anti-wetting properties, Teflon ® AF 2400 is coated on the membrane surface. The effects of coating on membrane morphology, performance and anti-wetting properties have been thoroughly investigated. With an optimal coating condition (0.025 wt% of Teflon ® AF 2400, 30 s), a super-hydrophobic surface with a contact angle of 151 o is achieved. The resultant membrane shows an increase of 109% in liquid entry pressure (LEP) with a slight sacrifice of 21% in flux. Long term direct contact MD tests have confirmed that the Teflon ® AF 2400 coated membrane has enhanced stability with an average flux of 21 kg m-2 h-1 and rejection of 99.99% at 60 ° C for desalination application.

Shell and lumen side flow and pressure communication during permeation and filtration in a multibore polymer membrane module

“…Due to their superior tensile properties, multibore membranes have found their way into many applications such as drinking water production and seawater desalination [1,2,5], and wastewater and surface water filtration (direct contact membrane distillation [3,6,7] and vacuum membrane distillation [8][9][10]).…”

PVDF membrane assisted by modified hydrophobic ZnO nanoparticle for membrane distillation

“…They found that by changing the content of the particles can be increased the water contact angle of the membrane surface. Lu and coworker have used porous PVDF tri‐bore hollow fiber membrane for membrane distillation and then have coated Teflon AF2400 on the membrane surface to improve its antiwetting properties. The obtained membranes exhibited high flux without an occurrence of pore wetting.…”

Development of Novel ECTFE Coated PP Composite Hollow-Fiber Membranes

“…There are several parameters that positively contribute to the success of the coating [25][26][27]: (i) the PP hollow fibers employed as support; its roughness facilitated the immobilization of ECTFE, its hydrophobicity facilitated the adhesion with the coating agent, whereas the chemical and thermal stability of PP ensured the survival of the hollow fibers from the harsh condition of the dip-coating; (ii) the excellent film-forming properties of ECTFE allowed the preparation of homogeneous coatings for the preparation of the protection layers; (iii) the solvent NMP facilitated the solubility of ECTFE at low temperature and enabled the preparation of polymeric ECTFE solution that quickly underwent demixing as a consequence of decreasing temperature of a few degrees, thus facilitating the Figure 3c); it can be seen that novel composite membranes present a less porous surface than PP hollow-fibers as a consequence of the deposition of ECTFE on the PP membrane support during the dip-coating process. This effect was also observed using the most diluted ECTFE polymeric solution (1 wt % of ECTFE).…”

“…In fact, ECTFE/PP composite membranes prepared using diluted concentration of ECTFE and short time of treatment (i.e., dip-coating) exhibited a hierarchical structure made of valleys entrapping air forming a gas-liquid interface with the feed solution, and resulting in a highly hydrophobic surface [25][26][27]. On the other hand, the hierarchical structure disappeared on increasing the concentration of ECTFE and time of dip-coating led to less porous and smoother surfaces with lower hydrophobic character.…”