Preparation And Pervaporation Of A Poly (Methyl Methacrylate-co-acrylic Acid)/montmorillonite Organic-inorganic Hybrid Membranes

Pervaporation is a new type of separation technology, the application of which in organic mixture separation is of energy-saving and environment-protection significance. In this paper, preparation and pervaporation of poly (methyl methacrylate- co-acrylic acid)/montmorillonite (P(MMA-co-AA)/MMT) inorganic-organic hybrid membranes for separation xylene isomers were investigated. And we also discussed by the pervaporation dissolution-diffusion mechanism of pervaporation performance.Fistly, montmorillonite was modified with cetyltrimethylammonium bromide by using an ion-exchange reaction. Poly (methyl methacrylate-co-acrylic acid)/montmorillonite hybrid materials were synthesized via emulsion polymerization initiated by redox initiator consisting of modified MMT and K2S2O3, and used as membranes for the separating xylene isomers mixtures by pervaporation. The organic montmorillonite was prepared using an ion-exchange reaction between the MMT silicate layers and hexadecyl trimethyl ammonium bromide (CTAB), which was tested by means of XRD and FTIR. Property and dispersion of MMT in P(MMA-co-AA) were investigated by means of XRD, which showed that MMT layers were exfoliated in the copolymer. The TGA curves showed the thermal stability of hybrid materials was increased due to the intercalation of MMT clays into P(MMA-co-AA) polymer, which also proved the existence of the interaction between inorganic and macromolecule.The membranes consisting of different MMT contents were used to separate p-/o-xylene. The swelling properties of the membrane in pure xylene and the diffusion coefficient of xylene molecule in the membrane were tested, the result was showed that diffusion coefficient of p-xylene was much larger than that of o-xylene, the pervaporation process was controlled by diffusion. The effects of the MMT contents in the hybrid membranes and feed temperature or feed concentration on the pervaporation performance of the hybrid membranes were investigated. The pervaporation performance of hybrid membranes was superior to pure P(MMA-co-AA) membrane. the maximum value of the separation factor reached 1.314 when MMT content was 6 wt%. The configuration of hybrid membranes, feed concentration and membrane structure were important factors to results of pervaporation flux and separation factor. In the increasing of feed temperature, the variety of the permeate flux J of hybrid membranes was accorded with Arrhenius equation, it is observed that the activation energy of o-xylene passing by the hybrid pervaporation membrane was higher than that of p-xylene. For different concentration of feed mixtures, it was observed that in p-/o-xylene mixture the selectivity of membrane changed with the increasing of p-xylene concentration. In this course, the control factor changed along with selectivity in dissolution-diffusion mechanism.