Pollutants removal from wastewaters through membrane distillation

Abstract The Sweeping Gas Membrane Distillation process is considered for the treatment of wastewaters containing volatile organic compounds such as acetone and ethanol. The separation technique is based on the use of microporous hydrophobic membranes under conditions of non wettability, in which the membrane separates an aqueous phase from a stripping gas. A wide experimental investigation is performed to study the role of temperature, composition and flow rate of the liquid phase and the influence of the sweeping gas flow rate. Performances of flat PTFE membranes are studied in the case in which dry nitrogen is used as stripping agent. Liquid feed flow rate as well as nitrogen flow rate are identified as the major design quantities since they greatly affect the separation efficiency. A simplified mathematical model is developed to describe multicomponent mass transfer in the gas phases, in which a pseudo-binary diffusion approach is assumed; molecular diffusion is considered as the prevailing transport mechanism through the membrane. The results obtained are compared with the experiments and the validity range of the model is defined.

[1]  Mohamed Khayet,et al.  Theory and experiments on sweeping gas membrane distillation , 2000 .

[2]  Thomas K. Sherwood,et al.  Absorption and Extraction , 1952 .

[3]  C. Gostoli,et al.  Thermal effects in osmotic distillation , 1999 .

[4]  P. Sheng,et al.  Theory and Simulations , 2003 .

[5]  C. Gostoli,et al.  Gas membrane extraction of ethanol by glycols: Experiments and modelling , 1995 .

[6]  G. C. Sarti,et al.  Heat and mass transfer boundary layers in radial creeping flow , 1994 .

[7]  M. C. Porter.  Concentration Polarization with Membrane Ultrafiltration , 1972 .

[8]  Mohamed Khayet,et al.  Thermal boundary layers in sweeping gas membrane distillation processes , 2002 .

[9]  Giulio C. Sarti,et al.  A desalination process through sweeping gas membrane distillation , 1987 .

[10]  M. C. García-Payo,et al.  Separation of binary mixtures by thermostatic sweeping gas membrane distillation: II. Experimental results with aqueous formic acid solutions , 2002 .

[11]  Eric Favre,et al.  Vacuum versus sweeping gas operation for binary mixtures separation by dense membrane processes , 2004 .

[12]  Giulio C. Sarti,et al.  Low energy cost desalination processes using hydrophobic membranes , 1985 .

[13]  Edward L Cussler,et al.  Diffusion: Mass Transfer in Fluid Systems , 1984 .

[14]  Mohamed Khayet,et al.  Theoretical and experimental studies on desalination using the sweeping gas membrane distillation method , 2003 .

[15]  M. C. García-Payo,et al.  Separation of binary mixtures by thermostatic sweeping gas membrane distillation: I. Theory and simulations , 2002 .

[16]  Won Hi Hong,et al.  Effect of operating variables on the flux and selectivity in sweep gas membrane distillation for dilute aqueous isopropanol , 2001 .

[17]  Mohamed Khayet,et al.  Nature of flow on sweeping gas membrane distillation , 2000 .

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