Configurational-bias grand-canonical transition-matrix Monte Carlo simulations are conducted to investigate various thermophysical properties, such as phase coexistence, critical properties, density and orientation profiles of liquid and vapor phases, and vapor-liquid surface tension of methane, ethane, propane, n-butane, and n-octane in bulk and slit pores of graphite and mica surfaces. An exponential-6 (exp-6) model is used for the investigation of normal alkanes with a cutoff radius, 15 Å. It is found that the surface tension of the bulk n-alkane, C 1 -C 4 , based on a truncated exp-6 model, agrees reasonably well with the experimental data. Critical properties are reported by means of the rectilinear diameter approach and least-squares technique. The shift in the critical temperature under confinements follows more than two linear regimes with an inverse in the slit width, as the slit width approaches the two-dimensional limit. This is contrary to what has been previously reported in the literature. The behavior of the critical temperature shift is sensitive to the nature of the surface. The critical density, on the other hand, fluctuates with a decrease in the slit width. The shift in the critical vapor pressure continuously increases with a decrease in the slit width toward the two-dimensional value and becomes constant for pore sizes less than 5 Å for the fluid studied in this work. Corresponding state plots suggest that the deviation of the saturation vapor pressure from the bulk saturation pressure under confinement is positive for large pores and negative for smaller pores. Vapor-liquid surface tension values for n-alkanes, in both types of slit pores, are computed via the finite-size scaling method of Binder and compared with their bulk values. Our investigation reveals that under slit-pore confinement the vapor-liquid surface tension decreases many fold.
Cellulose, an important cell wall polysaccharide, which is replenished constantly in nature by photosynthesis, goes waste in a lion's share in the form of pre-harvest and post-harvest agricultural losses and wastes of food processing industry. These cellulose wastes have an immense potential to be utilized for the production and recovery of several products and ingredients in food application. In this present study, a wide spectrum of researches in the arena of properties of cellulose, hemicellulose and lignin; their degradation; sources and composition of cellulosic and lignocellulosic wastes of agriculture and food industry; present status of converting them into value-added products of food applications; constraints in their conversions and future prospects therein has been reviewed in details. The study has encompassed production of biomass for various utilization and production and recovery of protein and amino acids, carbohydrates, lipids, organic acids, foods & feeds and other miscellaneous products.
An aqueous solution of CaCl2 as a model system has been used to develop the mechanism of how a highly water-soluble molecule can be synthesized as a solid nanoparticle with controlled diameter. This was achieved by first dissolving CaCl2 in nanometer-sized water drops of a water-in-oil (w/o) microemulsion system and later precipitating it as CaCl2 nanoparticles during the evaporation of the microemulsion. Nanoparticles were found by transmission electron microscopy (TEM) and atomic force microscopy (AFM) to increase in mean diameter from 25 to 88 nm as the diameter of a templating microemulsion droplet increased from 1.6 to 4.5 nm. The droplet size was varied by increasing the water to surfactant molar ratio (R) from 2 to 10. Variation of the absolute surfactant concentration, in itself, did not alter the particle size. From these findings, we propose that the CaCl2 nucleus forms during evaporation by heterogeneous nucleation on the surfactant headgroups of some of the drops. The nucleus then grows by the remaining dissolved CaCl2 molecules in the drop. This is followed by the addition of CaCl2 molecules contributed by those surrounding drops, which have no nucleus. The diameter of the final nanoparticle therefore exceeds that of the initial water drop. The number of such contributing drops (within a hypothetical contributing region around a drop containing a nucleus) was estimated by equating the timescales of CaCl2 nucleation with that of the Brownian diffusion of drops in the oil medium. Calculations based on this new concept quantitatively explained our experimental data on increasing the mean nanoparticle diameter with drop diameter. The final solid nanoparticle product is coated with surfactant, so it can be easily resuspended in any other solvent and used as and when required.
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