Vinita Dubey

Active carbon for removal of toxic chemicals from contaminated water

Coconut charcoals of different grades were studied for assessing the removal efficiency of chemical warfare (CW) agents from aqueous solutions. Oxygen analogue of sulphur mustard and phenol were used as model compounds for CW agents for adsorption studies. Freundlich and Langmuir adsorption isotherms were plotted. Equilibrium constant and maximum adsorption capacity for carbons were computed from the isotherm data. These studies enabled identification of an activated carbon suitable for use in reverse-osmosis water filtration systems.

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.

Sorption of sulfur mustard and its oxygen analog in black and nonblack‐filled butyl rubber membranes

Butyl rubber (IIR) membranes containing a 0–50% volume fraction of carbon black (GPF N660) or nonblack fillers (talc/precipitated CaCO3/fullers earth) were prepared by solution casting and evaluated for permeation resistance to the vesicant, bis(2-chloroethyl)sulfide, or sulfur mustard (SM) and its oxygen analog (OA), bis(2-chloroethyl)ether. The diffusivity of the chemicals was determined from the breakthrough time (BTT), obtained using the spot disc test and a gravimetric method. The permeation parameters, calculated from the sorption data, were used to determine an optimum filler content for maximum protection against SM. To investigate the effect of carbon loading on the permeation properties of IIR, the permeation of SM and OA in carbon-loaded black membranes was compared with nonblack membranes and interpreted in terms of the dispersion of carbon in the membranes.

Research trends in the degradation of butyl rubber

The present review surveys, integrates and gives a bibliographic account of studies carried out on the degradation of butyl rubber over the last few decades. Our objective was to extract the useful information from such studies. As a large fraction of the related literature is in inaccessible journals, many of which are not readily available in English translation, this paper should help in presenting an overview and insight into the nature of the work being done in the field. The effects of thermal and thermo-oxidative conditions, mechanical stresses (during processing and ultrasound treatment), catalysts, chemicals, ozone and radiation on the structure, and physicomechanical properties of butyl rubber have been discussed. This rubber was chosen as a representative elastomer in order to illustrate some trends in the degradation studies of other rubbers.

Diffusion and sorption of sulfur mustard and bis(2-chloroethyl)ether in elastomers: A comparative study

Bis(2-chloroethyl)ether, a nonvesicant and easy to handle chemical, was proposed as a model compound for the vesicant sulfur mustard (SM) in routine permeation testing of protective devices. The proposition was based on detailed studies on sorption of these chemicals in elastomers. From the sorption plots and permeation parameters, it was found that the model compound diffuses faster than SM, and the diffusion follows Fickian kinetics. Free volume models, such as those developed by Lee and Salame, together with solubility and thermodynamic interaction parameters, validated the observed sorption phenomenon and afforded a criterion for predicting the barrier properties of elastomers.

Sulphur mustard induced changes in surface relief features, mechanical and barrier properties of elastomer membranes

Influence of sulphur mustard (SM), a chemical warfare agent, and its oxygen analogue (OA), on surface relief features, mechanical properties and protection afforded by elastomeric membranes was investigated. The objective of the study was to assess the SM induced deterioration in the performance of the protective barrier against chemical hazard. Strain at break increases after exposure to SM in the elastomers studied, possibly due to plasticization. SM also induces microcracks in nitrile rubber (NBR) and natural rubber (PI) besides causing leaching of the compounding ingredients in the latter. This results in lowering of breakthrough time (BTT) of the permeant SM and hence a drop in the protection afforded by the elastomer membrane. Decontamination of the membrane using bleaching powder and boiling water for two hours helps in approaching the initial BTT value.

Studies on the thermal degradation of butyl rubber

Abstract Butyl rubber was pyrolysed under an inert atmosphere in a furnace-type pyrolyser at 400°C. The pyrolysate was trapped cryogenically and analysed by GC, GC/MS and GC/FT-IR. Based on these data, a mechanism for the thermal degradation of butyl rubber is proposed. The effect of temperature on the reative yields of the major decomposition products was also studied.