Udaya S. Toti

Pervaporation separation of water–isopropanol mixtures using ZSM‐5 zeolite incorporated poly(vinyl alcohol) membranes

A solution technique was employed to prepare ZSM-5 zeolite incorporated poly(vinyl alcohol) (PVA) membranes for the pervaporation separation of water-isopropanol mixtures. The membranes were characterized by Fourier transform infrared spectroscopy and differential scanning calorimeter. Glass transition temperatures of the membranes varied from 102 to 110°C, with increasing zeolite content of the membrane. The effect of zeolite loading and feed composition on pervaporation performance of the membranes was analyzed. The membrane containing 6 mass% of zeolite gave the highest separation selectivity of 216 for 10 mass % of water containing feed mixture at 30°C. Increase in water selectivity of the membrane was explained as due to a reduction in free volume by increasing zeolite content of the membrane. Separation selectivity and permeation flux data are dependent on water composition of the feed mixture, but are comparatively less dependent on temperature. The hindrance of water permeation at higher composition of water in the feed mixture was explained as due to the formation of clusters of water molecules. The overall activation energy and preexponential factors were calculated using Arrhenius equation. Pervaporation data have also been explained on the basis of thermodynamic parameters calculated by using Arrhenius equation as well as relationship proposed by Ping et al.

Pervaporation separation of water–acetic acid mixtures using polymeric membranes

Acetic acid is one of the basic chemical commodities having great industrial importance and its recycling after separation from aqueous stream is industrially important. In industrial unit operations, wastewater is almost always contaminated with acetic acid, the separation of which is difficult by conventional distillation methods because of their close relative volatility. Thus the conventional extractive distillation methods to separate them become expensive since they consume high energy. Due to these reasons chemical industries are always looking for viable alternative methods to separate them. Pervaporation (PV) separation, a technique that is based on membrane processes, becomes more attractive in solving this problem because this process is more economical and environmentally clean. This review summarizes the published literature on PV separation of water–acetic acid mixtures and compares the important published results from 1990 to date.

Ultrasonic and refractometric studies on polystyrene in 1,4-dioxane + tetrahydrofuran mixtures at 25°C

Using the results on density, refractive index and ultrasonic velocity of polystyrene solutions in binary mixtures of 1,4-dioxane and tetrahydrofuran (THF) at 25°C, Raos constant, relaxation strength, space-filling factor, van der Waals constants, free volume and molar refractivity have been calculated. These results are discussed to understand the thermodynamic interactions of polystyrene in 1,4-dioxane and THF mixtures.