Sujata F. Harlapur

A review of polymeric geosynthetics used in hazardous waste facilities

Abstract The generation of hazardous wastes from various sources including chemical industries, hospitals, households, etc., is a worldwide problem and is particularly acute in the United States. The petrochemical and refinery industries produce about 70% of this waste. Geographically, the greatest production of hazardous wastes is known to occur along the United State Gulf coast. Presently, it is estimated that about 80% of the total waste remains toxic for years or even centuries. Inappropriate disposal of these wastes on land creates the risk of contaminating ground water and vegetation causing adverse health effects. This review addresses the geotechnical aspects of the problems related to the management of hazardous waste by the use of polymeric materials as ‘barriers’. Important findings of research efforts on this topic from 1980 through mid-1994 are discussed. The review gives an awareness to the general public and addresses points of interest to field engineers and technologists for the proper handling of wastes by the use of the polymeric geosynthetics acting as membranes or barriers.

Sorption kinetics and diffusion of alkanes into tetrafluoroethylene/propylene copolymer membranes

Sorption kinetics and diffusion of hexane, heptane, octane, nonane, decane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethylene/propylene copolymer membranes were studied using the gravimetric sorption method at 30, 45, and 60°C. Coefficients of diffusion were calculated from Ficks equation. From these data, the permeability coefficients were obtained. Analytical solutions of Ficks relations were used to estimate the liquid concentration profiles into the polymeric membranes at different times. The profiles of liquid concentrations were also simulated for the polymer-solvent systems using the numerical simulation method. Activation parameters for diffusion and sorption were evaluated and these results are discussed in terms of the molecular sizes and geometries of liquids (i.e., shape) as well as temperature. The diffusion coefficients follow a systematic decrease with increasing size of the penetrant molecules. The activation energies i.e., E D values, increase with increasing size of n-alkanes.

A study on molecular transport of organic esters and aromatics into viton fluoropolymers

Molecular transport of organic liquids into Viton fluoropolymers has been investigated by a sorption-desorption gravimetric method. Diffusion coefficients have been calculated from Ficks equation. The sorption-desorption results have been used to calculate the concentration profiles by solving Ficks diffusion equation under suitable boundary conditions. A numerical method based on the finite difference technique was also used to calculate the concentration profiles of liquids as a function of sorption time and thickness of the Viton fluoropolymers. The dependence of sorption, desorption, diffusion, and permeation properties of the liquids on temperature showed a significant effect. The Arrhenius activation parameters have been estimated for diffusion, permeation, and sorption processes. The experimental and calculated results are discussed to study the type and nature of interactions between Viton fluoropolymers and the solvent molecules.

Sorption/desorption and diffusion kinetics of ketones and nitriles into fluoropolymer membranes

Analysis of sorption/desorption and diffusion kinetics of ketones and nitriles at 25, 44, and 60°C into three Du Ponts VITON fluoropolymer membranes loaded with different amounts of carbon black has been undertaken by use of a sorption/ desorption technique. The transport results are affected by the percent loading of carbon blacks. Diffusion coefficients have been calculated from Ficks equation. These results show a decrease with increasing amount of carbon black. Experimental results have been analyzed by considering swelling of the membranes. Sorption/desorption results have been analyzed from a calculation of the concentration profiles, which are obtained from the analytical solution of Ficks equation. These results have been compared with a numerical solution based on the finite difference method.

Synthesis, characterization and evaluation of 1,2-bis(2,4,6-trinitrophenyl) hydrazine: A key precursor for the synthesis of high performance energetic materials

1,2-Bis(2,4,6-trinitrophenyl) hydrazine (3) is one of the precursors in the synthesis of an important energetic material viz., hexanitrazobenzene. The simple and convenient lab scale synthesis of title compound (3) was carried out by the condensation of picryl chloride (2) with hydrazine hydrate at 30-50 degrees C in methanol based on the lines of scanty literature reports. Picryl chloride was synthesized by the reaction of picric acid (1) with phosphorous oxychloride based on the lines of reported method. The synthesized compound (3) was characterized by IR and 1H NMR spectral data. Some of the energetic properties of the synthesized compound have also been studied. The theoretically computed energetic properties of the title compound (3) indicated the superior performance in comparison to tetranitrodibenzo tetraazapentalene (TACOT) and hexanitrostilbene (HNS) in terms of velocity of detonation.

Transport characteristics of fluoroelastomers by ketones and nitriles

Abstract Solvent resistivity and diffusion of the 3M fluoroelastomers, viz. FC-2179 and FLS-2650 have been studied over the temperature interval of 30–60°C using a gravimetric sorption method. Ficks equation was used to calculate diffusion coefficients. The activation parameters for diffusion have been obtained from a temperature dependency of diffusion coefficients using the Arrhenius relationship. Concentration profiles of liquids at different penetration depths of the polymer samples for different times have been obtained both from an analytical solution of Ficks equation and by using a numerical method. Experimental sorption results and the computed quantities have been discussed in terms of the nature of the penetrant molecules and the morphology of the polymers.

An investigation of the long-term sorption kinetics and diffusion anomalies of chloroalkanes into tetrafluoroethylene/propylene copolymer membranes at 30, 45 and 60°C

An investigation of the long-term sorption kinetics and diffusion anomalies of dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene and tetrachloroethylene into the tetrafluoroethylene/propylene copolymer membranes has been carried out using gravimetric sorption technique at 30, 45 and 60°C. Coefficients of diffusion and permeation have been calculated from Ficks equation. Analytical solutions of Ficks equation have been used to compute liquid concentration profiles into polymeric sheet membranes at different times. Activation parameters for diffusion and sorption have been evaluated and these results are discussed in terms of the molecular size of the liquids and the temperature. The diffusion coefficient and activation energy for diffusion do not exhibit any systematic dependence on the size of the penetrant molecules, but these are mainly influenced by the nature of chloroalkanes.

Sorption and Diffusion of Organic Liquids into Fluoroelastomer Membranes

Abstract Sorption and diffusion of organic liquids into fluoropolymer (FC-2179) membranes have been investigated from 30 to 60°C using a gravimetric method. Diffusion coefficients, percent mass uptake, and apparent activation energies for the transport processes have been estimated. Diffusion coefficients of the liquids into the membrane have been computed from Ficks relation. A Flory–Huggins-type interaction parameter was obtained from the solubility parameter concept. Furthermore, the activation parameter values and heat of sorption data have been studied in terms of heat of mixing. The values of diffusion coefficients did not show any considerable dependence on solvent concentration. However, solvent transport as analyzed from an empirical equation was found to be of the anomalous type. Molecular transport also showed a dependence on the chemical nature of the liquids. The concentration profiles of liquids have been calculated at different penetration depths of the membrane at different time intervals...

A review on the sustained release of cardiovascular drugs through hydroxypropyl methylcellulose and sodium carboxymethylcellulose polymers

In modem medical technology, several new types of polymeric membrane have been used for the sustained release (SR) of cardiovascular drugs. When these drugs are delivered continuously at a sustained rate over a predetermined time, a uniform and constant blood level is achieved due to the smaller amount of drug, thereby minimizing the side-effects. Among the many polymeric systems used in the SR of cardiovascular drugs, research on the usage of cellulose-based materials has been exhaustive. Of these, tremendous interest has been focused on the use of hydroxypropyl methylcellulose (HPMC) and sodium carboxymethylcellulose (Na CMC) polymers as SR devices. This review critically discusses the useful published literature results on HPMC and Na CMC polymeric matrices for the period 1970-1997 in the area of SR of cardiovascular drugs.

Sorption and diffusion of organic liquids into engineering fluoroelastomer membranes in the temperature interval 30–60 °C

Abstract Sorption and diffusion of dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, 1,4-dioxane and dimethylacetamide into four (FA-100S, FA-150P, FC-2179 and FLS-2650) engineering fluoroelastomeric membranes have been studied at 30, 45 and 60 °C using a gravimetric sorption method. A Fickian transport kinetics has been observed in all the cases and the diffusion/sorption results have shown a dependence on the type of polymer used and the temperature. Concentration profiles of liquids have been calculated from the analytical solution of Ficks diffusion equation. Arrhenius activation parameters have been calculated and the results are discussed with regard to the polymer-solvent interactions.