Prediction of Binary Gas Adsorption of CO₂/N₂ and Thermodynamic Studies on Nitrogen Enriched Nanostructured Carbon Adsorbents

Pure component adsorption isotherms for CO₂ and N₂ on the prepared nitrogen enriched carbon were evaluated using a static volumetric analyzer at four different adsorption temperatures ranging from 30–100 °C and were then correlated with three pure component adsorption isotherm models, namely, Langmuir, Sips, and dual-site Langmuir (DSL) models. Adsorption equilibria of binary CO₂–N₂ adsorption was then predicted by extending Sips and DSL equations empirically along with the usage of ideal adsorbed solution theory and was compared with experimental data obtained from the breakthrough curves through various phase diagrams. Breakthrough data for binary system were obtained at four different CO₂ feed concentrations (5–12.5% by volume) and four adsorption temperatures (30–100 °C) using a fixed-bed reactor. Among three adsorption isotherms models used to investigate the equilibrium data of pure component system, Sips and DSL adsorption isotherm models fitted well, indicating energetically heterogeneous adsorbent surface. However, for the binary adsorption system, their extended forms highly under-predicted the amount of CO₂ adsorbed over the complete temperature and feed concentration range because of the difference in adsorptive strengths of CO₂ and N₂ molecules. Also, ideal adsorbed solution theory was not able to describe the mixed-gas adsorption equilibria. Total adsorbed amounts were found to increase with CO₂ gas phase molar fraction implying positive deviations from Raoult’s law with asymmetric <i>x–y</i> diagrams. Thermodynamic functions such as molar Gibbs free energy change, entropy change, and enthalpy change were evaluated numerically for pure component system. They confirmed the feasibility of adsorption process and indicated the formation of more ordered configuration of CO₂ molecules on adsorbent surface and hence exhibited higher heats of adsorption as compared to N₂

Photocatalytic degradation of 3,4-dichlorophenol using TiO₂ in a shallow pond slurry reactor

75-81In the present study, the TiO2 mediated photocatalytic degradation of 3,4-dichlorophenol, as a model compound, has been investigated using a low cost non-concentrating shallow pond slurry reactor at laboratory scale under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV-spectroscopic analysis, decrease in COD values and increase in chloride formation as a function of irradiation time. The effect of pH, catalyst loading, substrate concentration, UV intensity, aperture to volume ratio of the reactor and presence of electron acceptors such as hydrogen peroxide besides molecular oxygen, on degradation, was studied. The degradation rates were strongly influenced by some of these parameters. The optimum parameters for maximum degradation were determined. The degradation of 3,4-dichlorophenol can be emulated in sunlight using a similar large-scale shallow pond reactor for the solar detoxification in open atmosphere

Effect of moisture content on the engineering properties of Jamun (Syzgium cuminii) seed

Engineering properties as a function of moisture content are important for food processing and equipment designing, assessment of other properties, and for the product quality determination. Different engineering properties of Jamun seeds depending upon the moisture content in the range of 11.54 to 26% (db) were studied. It was noted that various properties like, length (L), breadth (B), thickness (T), and geometric mean diameter (D-g) increased linearly with increasing moisture content. The seed surface area (S-a), seed volume (V), thousand seed mass (M-1000), increased from 220.5 to 303.2 mm(2), 257.2-443.7 mm(3), 0.28-0.37 kg, respectively, with increasing moisture content. As the moisture content increased, bulk density (rho(b)) and true density (rho(t)) decreased from 899.33 to 778.66 and 1,270.89 to 1077.75 kg/m(3), respectively, while porosity increased nonlinearly from 26.2 to 27.7%. With the increased moisture in seeds, the angle of repose increased linearly from 27.4 to 33.5 degrees. Static coefficient of friction also increased from 0.23 to 0.40, 0.29 to 0.42, and 0.57 to 0.73 for glass, cardboard and plywood surfaces, respectively, with the increasing moisture content. Practical Applications The physical properties of Jamun seeds will be helpful in machine designing for industrial processing and fabrication of postharvest handling equipment like sorter, grader, collector, dryer, pulper, and grinder. These properties may help in designing of grinding, packaging machines, and storage structures