ИСТИНА

There are several methods that currently used for water-organic liquid mixtures separation, for example distillation, adsorption, pervaporation. Besides these methods membrane vapor separation technique is widely investigated in present time for organics removal from water. This technique can be especially effective for separation of diluted water-organic liquid mixtures such as waste mixtures of technogenic origin containing volatile organic compounds (VOCs), liquid phase during bioalcohols production (bioethanol, biobutanol) and other. Due to the low concentration of organics and high content of water traditional distillation becomes too much energy consumable. Pervaporation is more preferable process in this case since membrane can provide removal of organics from water with noticeably higher selectivity. Membrane vapor separation method is good alternative to pervaporation, it suggests the separation of vapor phase that is formed over solution. The most of water-organic solutions have strong positive deviation from Raoult’s law in the region of low organic concentration therefore vapor phase is highly enriched by organic component compared to liquid phase. In this case separation of vapor phase can be carried out by application of both types of membranes: organic-selective membrane or water-selective membrane. Since water-selective (hydrophilic) membranes usually demonstrate very high selectivity towards organics the high concentration of organic vapor in retentate stream can be achieved. Moreover, membrane vapor separation is free from such disadvantages of pervaporation as temperature and concentration polarization and membrane fouling. Hence the treatment of this type of streams remains unsolved at the source in particular for small or medium flow rates and the waste water has to be treated elsewhere preferably with bioprocess when the VOCs is biodegradable; nevertheless the industrial water used cannot be recycled. Thus a membrane treatment of the VOCs in the gas phase, i.e. after an initial stripping step, seemed to be an interesting alternative because the effect of the polarization is known to be less severe in such conditions. Other example includes the diluted organic-water solutions which are convenient products of biomass treatment to biofuels (e.g., ABE fermentation). The alcohol recovery method considered is based on combination of the gas stripping (convenient process) with membrane vapor separation (with preferable butanol or water vapor permeability). In comparison with known membrane pervaporation method the suggested one possesses such advantageousness as an expanded membrane module area and resistance to fouling. Main attention is put on fundamental aspects of separation: (1) the contribution of liquid/vapor phase transition and (2) vapor selective properties of organophilic membranes. In the frames of proposed approach two classes of hydrophobic polymers are considered: (1) alcohol-selective glassy polymers based on 1, 2-disubstituted polyacetylenes (glassy polymers with very high free volume) and (2) water-selective glassy polyolefins. Presentation demonstrates data of vapor permeability in relation to organics vapors (toluene, acetone, dicloromethane, ethanol, butanol) and to water vapor at different temperatures and the solution composition. Apparent activation energy and temperature parameter of permeability are obtained and considered. The methodology of study can be used for the systematic research of the vapor permeability membrane properties influence on separation of multi- component liquid mixtures with taking into account of liquid/vapor equilibrium. Vapor phase membrane technology can be considered as well controlled prospective technique for separation of liquids.