Search results for "Exothermic process"
showing 6 items of 6 documents
Origin of peak asymmetry and the effect of temperature on solute retention in enantiomer separations on imprinted chiral stationary phases
1995
Abstract In enantiomer separations of d - and l -phenylalanine anlilide ( d,l -PA) on l -PA-imprinted chiral stationary phases (CSPs), the use of an aqueous buffer-organic solvent mixture as mobile phase resulted in improved column efficiency compared with what has previously been observed using mobile phases containing acetic acid as modifier. The dependence of the chromatographic parameters on flow-rate and sample load was studied. A strong dependence of the asymmetry factor ( A s ) of the l -form on sample load and a weak dependence on flow-rate indicate that the non-linear adsorption isotherm is the main reason for the broad peaks observed in this system. Depending on the method used fo…
Energy management of a thermally coupled fuel cell system and metal hydride tank
2019
International audience; Being produced from renewable energy, hydrogen is one of the most efficient energy carriers of the future. Using metal alloys, hydrogen can be stored and transported at a low cost, in a safe and effective manner. However, most metals react with hydrogen to form a compound called metal hydride (MH). This reaction is an exothermic process, and as a result releases heat. With sufficient heat supply, hydrogen can be released from the as-formed metal hydride. In this work, we propose an integrated power system of a proton exchange membrane fuel cell (PEMFC) together with a hydride tank designed for vehicle use. We investigate different aspects for developing metal hydride…
Potential use of activated carbon derived from Persea species under alkaline conditions for removing cationic dye from wastewaters
2017
Abstract The use of Persea americana has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. Chemical activation using phosphoric acid was employed for the preparation of the activated carbon (C-PAN). The BET surface area and the total pore volumes were found to be 1593 m2/g and 1.053 cm3/g, respectively. This study investigates the effect of some parameters like, dye concentration, adsorbent dose, contact time and pH for the best comprehension of the adsorption manner. Adsorption kinetic follows pseudo-second order kinetic model. Langmuir and Freundlich isotherms models were used to analyze the adsorption equilibrium data and the best fits to …
Helium Behavior in Oxide Nuclear Fuels: First Principles Modeling
2010
UO2 and (U,Pu)O2 solid solutions (the so-called MOX) nowadays are used as commercial nuclear fuels in many countries. One of the safety issues during the storage of these fuels is related to their self-irradiation that produces and accumulates point defects and helium therein. We present density functional theory (DFT) calculations for UO2, PuO2 and MOX containing He atoms in octahedral interstitial positions. In particular, we calculated basic MOX properties and He incorporation energies as functions of Pu concentration within the spin-polarized, generalized gradient approximation (GGA) DFT calculations. We also included the on-site electron correlation corrections using the Hubbard model …
Towards a microbial thermoelectric cell.
2013
Microbial growth is an exothermic process. Biotechnological industries produce large amounts of heat, usually considered an undesirable by-product. In this work, we report the construction and characterization of the first microbial thermoelectric cell (MTC), in which the metabolic heat produced by a thermally insulated microbial culture is partially converted into electricity through a thermoelectric device optimized for low ΔT values. A temperature of 41°C and net electric voltage of around 250–600 mV was achieved with 1.7 L baker’s yeast culture. This is the first time microbial metabolic energy has been converted into electricity with an ad hoc thermoelectric device. These results might…
Formation of As8 dimers in molecular solid-state arsenic
1997
Abstract Molecular yellow arsenic (y-As) consists of tetrahedral As 4 molecules that may be packed in various ways. All y-As modifications, both disordered and crystalline, are metastable and undergo irreversible transitions (polymerization) under action of heat and light, which cause a change in the nature of bonding in the molecules. Polymerization of y-As leads to the formation of amorphous arsenic (a-As) possessing a continuous random network structure. DTA studies show that polymerization is an activated exothermic process. The value of its enthalpy agrees satisfactorily with an estimate of the excess energy of strained ‘banana-shaped’ bonds in an As 4 molecule. Quantum chemical calcul…