SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2020, Vol. 28 ›› Issue (12): 3002-3010.DOI: 10.1016/j.cjche.2020.05.004

• Separation Science and Engineering • Previous Articles     Next Articles

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

M. Ajdar1, A. Azdarpour1, A. Mansourizadeh2, B. Honarvar1,3   

  1. 1 Department of Chemical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran;
    2 Department of Chemical Engineering, Membranne Science and Technology Research Center(MSTRC), Gachsaran Branch, Islamic Azad University, Gachsaran, Iran;
    3 Department of Civil Engineering, The University of Texas at Arlington, Arlington, TX 76019, USA
  • Received:2020-01-06 Revised:2020-04-15 Online:2021-01-11 Published:2020-12-28
  • Contact: A. Azdarpour, A. Mansourizadeh

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

M. Ajdar1, A. Azdarpour1, A. Mansourizadeh2, B. Honarvar1,3   

  1. 1 Department of Chemical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran;
    2 Department of Chemical Engineering, Membranne Science and Technology Research Center(MSTRC), Gachsaran Branch, Islamic Azad University, Gachsaran, Iran;
    3 Department of Civil Engineering, The University of Texas at Arlington, Arlington, TX 76019, USA
  • 通讯作者: A. Azdarpour, A. Mansourizadeh

Abstract: Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N2 permeation, overall porosity, critical water entry pressure (CEPw), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N2 permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m-1. CEPw of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m-2·h-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.

Key words: PVDF-HFP hollow fiber membrane, Ternary phase diagram, Membrane characterization, Sweeping gas membrane distillation, Ethylene glycol

摘要: Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N2 permeation, overall porosity, critical water entry pressure (CEPw), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N2 permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m-1. CEPw of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m-2·h-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.

关键词: PVDF-HFP hollow fiber membrane, Ternary phase diagram, Membrane characterization, Sweeping gas membrane distillation, Ethylene glycol