Chhaya Saxena

Pervaporation of binary water-ethanol mixtures through bacterial cellulose membrane

Abstract Cellulose membrane produced by the bacterium Acetobacter xylinum was deproteinated and investigated for pervaporation (PV) of binary water–ethanol mixtures. The membrane was characterised using elemental analysis, infra-red spectroscopy, scanning electron microscopy as well as for mechanical strength and sorption characteristics. A batch stirred cell was used to study the PV behaviour of water–ethanol mixtures through the membrane. The permeate flux, selectivity, PV separation index (PSI), solubility and degree of sorption were studied as a function of increasing ethanol concentration in the feed. The membrane was found highly selective to water. Even when the feed was rich in ethanol (>70% (w/w)) the permeate contained higher than 95% (w/w) of water. For feed compositions containing less than 30% water, the selectivity towards water was in the range of 125–287, the flux was greater than 100 g/m2 h and PSI was of the order of 104 g/m2 h.

Poly‐Schiff bases. III. Synthesis and characterization of polyesterazomethines

Ten new polyesterazomethines have been synthesized by solution polycondensation of five different diamines with 4,4′-[terephthaloyloxy]bis-3-ethoxybenzaldehyde and 4,4′-[isophthaloyloxy]bis-3-ethoxybenzaldehyde using dimethylacetamide in the presence of anhydrous LiCL. Fibrous polymers were precipitated by pouring the solutions into water. The polymerization proceeds rapidly to give highly viscous solutions. The resulting polymers were characterized by viscosity measurement, IR, x-ray diffraction study, elemental analysis, and DSC study. 1H-NMR spectra of some of the polymers were also recorded. The thermal stability of the polymers was evaluated by TGA and IGA study. Electronic spectra of the polymers were recorded in H2SO4.

Poly-schiff bases—II. Synthesis and characterization of polyetherketoimines

Abstract Six new poly-Schiff bases have been synthesized by solution polycondensation of six different diamines with 4,4′-aryl bis-(oxy)-bis acetophenone. The synthesized polymers were characterized by viscosity measurement, elemental analyses, i.r., X-ray diffraction, and differential scanning calorimetry. The thermal stability of the polymers was evaluated by thermogravimetric and isothermal gravimetric analysis. The polymers cured at a high temperature by the opening of C(CH3)N linkages. The electrical conductivities of the virgin and iodinedoped polymers are as high as 10−11 – 10−16 and 10−9 − 10−6 S/cm, respectively, at 30 °C. Variation in the electrical conductivity (σ) with temperature followed the empirical relation σ = σ 0 e −E a RT .

Poly-Schiff bases - IV. Synthesis and characterization of poly (etherazomethine)s

Twelve new poly(etherazomethine)s with linear structures were prepared by a conventional literature procedure by reacting six different diamines with two different bisaldehydes containing ether linkages in the backbone. The resulting polymers were confirmed by infrared (IR) elemental analysis and viscosity measurements. The thermal stability of the polymers was evaluated by thermogravimetry (TG) and isothermal gravimetric (IG) analyses. These polymers are reasonably good thermally and thermo-oxidatively stable. A semicrystalline behavior was noticed for these polymers by X-ray powder diffraction and differential scanning calorimetry measurements.

Kinetics of diffusion of water and dimethylmethylphosphonate through poly(dimethylsiloxane) membrane using coated quartz piezoelectric sensor

The mass sensing principle of quartz crystal has successfully been employed to study the diffusion of dimethylmethylphosphonate (DMMP) and water through a poly(dimethylsiloxane ) (PDMS) membrane. For this study a new permeation cell has been fabricated which houses a Cu(II) butyrate ethylenediamine-coated quartz crystal sensor. This development was motivated by the desire to measure the diffusion coefficients rapidly, precisely, and at different temperatures. Temperature dependence diffusion coefficients of DMMP and water are also evaluated using the same cell, which enables calculation of the activation energies for the diffusion process. From the diffusion and solubility data permeability coefficients of DMMP and water have been calculated. It is observed that PDMS membrane offers a selectivity for DMMP over water roughly by 13: 1 (i.e., P DMMP /P water > 13).