Pollutants removal from wastewaters through membrane distillation Original Research Article

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.