Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol-water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution.

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A polyimide blend system has been prepared from a base polyimide of BTDAODA by adding ε‐caprolactam at the poly(amic acid) stage where ε‐caprolactam undergoes polymerization to form nylon 6 during the thermal cyclodehydration of poly(amic acid). The blend has been characterized by elemental analysis. IR, 13C CPMAS NMR, XRD and simple chemical methods. The thermal analysis study (TGA and DTA) shows that the stability of the blend systems is more in the lower temperature region (up to 300°C) in comparison to the control polyimide system. The isothermal study at 400°C in inert atmosphere shows that the blend system is equally stable but the isothermal study in air at 400°C shows that the thermooxidative stability of the blend films (except BB 4) is higher. Also, isothermal study in air at 500°C shows more than 90% weight loss for all the films within 3 h, but in an inert atmosphere, the blend films show lower weight loss compared to the control film. Although the XRD pattern of all the blend and control films shows an amorphous character, the films developed some crystallinity when treated with boiling NMP where the blend films developed higher crystallinity.

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