Separation of ethanol/water mixtures by pervaporation through zeolite-filled polysulfone membrane containing 3-aminopropyltrimethoxysilane

Ethanol/water mixture is separated by pervaporation through a polysulfone (PSf) membrane filled with zeolite. The coupling agent effect of 3-aminopropyltrimethoxysilane (APTMS) on the preparation of PSf/zeolite membrane was also studied. APTMS enhanced the contact of zeolite particles with PSf chains and suppressed the formation of microvoids in polymer-zeolite interface. The effects of zeolite type, zeolite loading, feed composition, coupling agent concentration, and treatment time of zeolite surface modification on the pervaporation performance were investigated. The pervaporation performance of the zeolite-filled PSf membranes was strongly affected by the zeolite type. In addition, the molecular sieving effect of zeolite seemed to take place when coupling agent concentration and treatment time increased. Compared with the PSf membrane, the PSf/zeolite 13X/ APTMS membrane effectively improved the pervaporation performances.

The incorporation of zeolites into PSf induces important changes in the pervaporation separation performance of the composite membrane. In all cases, the incorporation of the hydrophilic zeolite caused an increase in the permeation rate but decrease in water concentration in the permeate. Adhesion between PSf and zeolite was found to be bad that led to decreasing of selectivity of the PSf/zeolite membrane. Surface modification of the zeolite’s external surface by means of a coupling agent (APTMS) resulted in a considerable improvement of the internal structure of PSf/zeolite membranes. It can be observed that the most promising approach for improving pervaporation properties of the PSf/zeolite membrane is the modification of zeolite by a higher coupling agent concentration combined with longer treatment time. Addition of zeolite 13X with appropriately surface modification to the PSf membrane appears to improve both permeation rate and water concentration in the permeate.