Removal of 1,1,1-trichloroethane from water using a polyvinylidene fluoride hollow fiber membrane module: Vacuum membrane distillation operation

Polyvinylidene fluoride (PVDF) hollow fiber membranes with an asymmetric structure have been prepared by the phase inversion method using dimethylacetamide (DMAc) as solvent and LiCl–H2O as additives and applied for volatile organic compounds (VOCs) removal from water. The membrane was characterized using scanning electron microscopy (SEM) for observing its microstructures and a gas permeation method for measuring its porosity, pore size and pore size distribution. The results have provided the conditions for tailor-made hollow fiber membranes with the desired morphology suitable for vacuum membrane distillation (VMD). Moreover, the structural parameters such as mean pore size and effective porosity determined are being used as parameters in the mathematical modeling of the VMD process. A hollow fiber membrane module was then fabricated using a selected PVDF hollow fiber membranes and applied for removal of 1,1,1-trichloroethane (TCA) from water. The effects of various operating parameters including downstream vacuum level, feed temperature, feed flow rate and TCA feed concentration on the performance of the module were investigated both theoretically and experimentally. A high feed temperature and/or a low downstream pressure favored the enhancement of TCA removal, but also yielded dramatically a high water permeation flux, resulting in an excessive dilution of the permeated VOC. Under optimal operating conditions, particularly the downstream vacuum level, feed temperature and feed flow rate, TCA removal efficiency up to 97% was achievable. A mathematical model, which takes into consideration of mass transfer resistances in both liquid and membrane phases, predicts well the TCA removal data in comparison with the experimentally observed results under the favorable operation ranges employed in vacuum membrane distillation.

[1]  I. Ortiz,et al.  Kinetic analysis of the vacuum membrane distillation of chloroform from aqueous solutions , 2000 .

[2]  Denis Roizard,et al.  Removal of volatile organic components (VOCs) from water by pervaporation: separation improvement by Dean vortices , 1998 .

[3]  Kang Li,et al.  Preparation and characterization of polyvinylidene fluoride (PVDF) hollow fiber membranes , 1999 .

[4]  Suhas P. Deshmukh,et al.  Effect of ethanol composition in water coagulation bath on morphology of PVDF hollow fibre membranes , 1998 .

[5]  Kang Li,et al.  Removal of H2S to ultra-low concentrations using an asymmetric hollow fibre membrane module ☆ , 2002 .

[6]  B. Min,et al.  A new technique for preparation of PDMS pervaporation membrane for VOC removal , 2002 .

[7]  Inmaculada Ortiz,et al.  Parallelism and differences of pervaporation and vacuum membrane distillation in the removal of VOCs from aqueous streams , 2001 .

[8]  John H. Montgomery,et al.  Groundwater Chemicals Desk Reference , 1989 .

[9]  Kang Li,et al.  Preparation of PVDF hollow-fiber membranes via immersion precipitation , 2001 .

[10]  J. Kong.  An improved gas permeation method for characterising and predicting the performance of microporous asymmetric hollow fibre membranes used in gas absorption , 2001 .

[11]  Gunnar Eigil Jonsson,et al.  Factors affecting flux and ethanol separation performance in vacuum membrane distillation (VMD) , 2003 .

[12]  X. Tan,et al.  Design of hollow fibre membrane modules for soluble gas removal , 2000 .

[13]  K. Sirkar,et al.  Removal of VOCs from air by membrane-based absorption and stripping , 1996 .

[14]  Giulio C. Sarti,et al.  Vacuum membrane distillation: Experiments and modeling , 1997 .

[15]  Giulio C. Sarti,et al.  Extraction of organic components from aqueous streams by vacuum membrane distillation , 1993 .

[16]  Corinne Cabassud,et al.  A new process to remove halogenated VOCs for drinking water production: vacuum membrane distillation☆ , 1998 .

[17]  S. Nakao,et al.  Hollow-fiber-type pore-filling membranes made by plasma-graft polymerization for the removal of chlorinated organics from water , 2001 .

[18]  L. Vane,et al.  Recent advances in VOCs removal from water by pervaporation. , 2003, Journal of hazardous materials.

[19]  Mohamed Khayet,et al.  Preparation and characterization of polyvinylidene fluoride hollow fiber membranes for ultrafiltration , 2002 .

[20]  X. Tan,et al.  Development of membrane-UV reactor for dissolved oxygen removal from water , 2001 .

[21]  R. E. Treybal.  Mass-Transfer Operations , 1955 .

[22]  G. Versteeg,et al.  Membrane–solvent selection for CO2 removal using membrane gas–liquid contactors , 2004 .

[23]  Fawzi Banat,et al.  Removal of benzene traces from contaminated water by vacuum membrane distillation , 1996 .