Pervaporation membranes can be classified into organic and inorganic membranes. NaA zeolite membrane, as an inorganic membrane, has well-defined zeolitic pores with high hydrophilicity. The pore size of NaA zeolite membrane is 0.42 nm, which is larger than water molecule (~ 2.9 A) and less than most of organic molecular diameters. Therefore, the membrane shows excellent permselectivity and flux for separation of water from organics. Compared to organic membranes, the zeolite membranes have several advantages including higher permeation flux, higher separation factor and better thermal/chemical stability.
During the separation process, the feed solvent is introduced to the feed side of the membrane, and the H2O is removed from the permeate side. The low pressure of the permeate side is maintained by the use of a vacuum pump. Water molecules are preferentially adsorbed on the surface of the membrane, and then permeate through NaA zeolite membrane layer. The driving force of the process is the difference in the partial pressures of water across the membrane. In the feed side, the dehydrated product can be achieved on the retentateï¼?and the H2O in the permeate side is condensed and drained.
Pervaporation process
The pervaporation process is not limited to the gas/liquid equilibrium of the solvent. It can achieve high-purity solvent with low energy consumption, and separate solvents which are difficult to be achieved by traditional separation methods such as distillation, extraction and adsorption. It has obvious advantages for separation of azeotropic or close azeotropic mixtures and dehydration of solvents with minor or trace water, which is a promising technology for substitution of traditional separation technologies. It has a promising application in energy, petrochemical industry, biological medicine, electronics, environmental protection and other fields.
