Structure and Thermochemistry of Perrhenate Sodalite and Mixed Guest Perrhenate/Pertechnetate Sodalite.

Treatment and immobilization of technetium-99 (99Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na8[AlSiO4]6(ReO4)2, and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na8[AlSiO4]6(ReO4)2-x(TcO4)x. Perrhenate was used as a chemical analogue for pertechnetate. Bulk analyses of each solid confirm a cubic sodalite-type structure (P4̅3n, No. 218 space group) with rhenium and technetium in the 7+ oxidation state. High-resolution nanometer scale characterization measurements provide first-of-a-kind evidence that the ReO4- anions are distributed in a periodic array in the sample, nanoscale clustering is not observed, and the ReO4- anion occupies the center of the sodalite β-cage in Na8[AlSiO4]6(ReO4)2. We also demonstrate, for the first time, that the TcO4- anion can be incorporated into the sodalite structure. Lastly, thermochemistry measurements for the perrhenate sodalite were used to estimate the thermochemistry of pertechnetate sodalite based on a relationship between ionic potential and the enthalpy and Gibbs free energy of formation for previously measured oxyanion-bearing feldspathoid phases. The results collected in this study suggest that micro- and mesoporous crystalline solids maybe viable candidates for the treatment and immobilization of 99Tc present in reprocessed nuclear waste streams and contaminated subsurface environments

Biofabrication : reappraising the definition of an evolving field

Biofabrication is an evolving research field that has recently received significant attention. In particular, the adoption of Biofabrication concepts within the field of Tissue Engineering and Regenerative Medicine has grown tremendously, and has been accompanied by a growing inconsistency in terminology. This article aims at clarifying the position of Biofabrication as a research field with a special focus on its relation to and application for Tissue Engineering and Regenerative Medicine. Within this context, we propose a refined working definition of Biofabrication, including Bioprinting and Bioassembly as complementary strategies within Biofabrication

Thermodynamics of hydrolysis of cellulose to glucose from 0 to 100 °C: Cellulosic biofuel applications and climate change implications

Hydrolysis of cellulose to glucose is a key reaction in renewable energy from biomass and in mineralization of soil organic matter to CO2. Conditional thermodynamic parameters, ΔhydG’, ΔhydH’, and ΔhydS’, and equilibrium glucose concentrations are reported for the reaction C6H10O5(cellulose) + H2O(l) ⇄ C6H12O6(aq) as functions of temperature from 0 to 100 °C. Activity coefficients of aqueous glucose solution were determined as a function of temperature. The reaction free energy ΔhydG’ becomes more negative as temperature increases, suggesting that producing cellulosic biofuels at higher temperatures will result in higher conversion. Also, cellulose is a major source of carbon in soil and is degraded by soil microorganisms into CO2 and H2O. Therefore, global warming will make this reaction more rapid, leading to more CO2 and accelerated global warming by a positive feedback

One-pot Synthesis of Pt Catalysts Supported on Al-modified TiO2

A facile, industrially viable, one-pot synthesis of 0.5-8 wt% Pt supported on 22 mol% Al-modified ana-tase with high surface area and thermal stability is presented. Four pathways were studied to deter-mine the effects of support properties on catalyst dispersion, and the highest dispersions were observed for high surface area materials containing 5-coordinate anatase. Systematic study of preparation vari-ables shows that low drying temperatures, slow calcination ramp rates, and slow reduction ramp rates further increased Pt dispersion and resulted in a more uniform Pt size distribution. Pt dispersions as high as 54% have been obtained using the one-pot method and 59% for Pt catalysts synthesized by dry impregnation. Statistically designed studies are needed to more completely determine the effects of synthesis variables and to optimize the dispersion and reduction of Pt supported on Al-modified ana-tase. Results presented in this paper show that this one-pot method and dry impregnation method us-ing our Al-modified anatase support are promising syntheses of highly dispersed Pt supported on stabi-lized titania. Our results demonstrate that the alumina-stabilized anatase support is superior to other anatase supports for (1) obtaining high Pt dispersions, i.e. more efficiently utilizing this expensive pre-cious metal, and (2) processes in which thermal stability is important due to its constant phase and pore structures at high temperatures. © 2014 BCREC UNDIP. All rights reservedReceived: 20th April 2014; Revised: 14th May 2014; Accepted: 10th June 2014How to Cite: Olsen, R.E., Bartholomew,C.H., Enfield, D.B., Woodfield, B.F. (2014). One-pot Synthesis of Pt Catalysts Supported on Al-modified TiO2. Bulletin of Chemical Reaction Engineering &amp; Catalysis, 9 (3): 156-167. (doi:10.9767/bcrec.9.3.6734.156-167)Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.3.6734.156-167</p

Laws of evolution parallel the laws of thermodynamics

We hypothesize that concepts from thermodynamics and statistical mechanics can be used to define summary statistics, similar to thermodynamic entropy, to summarize the convergence of processes driven by random inputs subject to deterministic constraints. The primary example used here is biological evolution. We propose that evolution of biological structures and behaviors is driven by the ability of living organisms to acquire, store, and act on information and that summary statistics can be developed to provide a stochastically deterministic information theory for biological evolution. The statistical concepts that are the basis of thermodynamic entropy are also true for information, and we show that adaptation and evolution have a specific deterministic direction arising from many random events. Therefore, an information theory formulated on the same foundation as the immensely powerful concepts used in statistical mechanics will provide statistics, similar to thermodynamic entropy, that summarize distribution functions for environmental properties and organism performance. This work thus establishes foundational principles for a quantitative theory that encompasses both behavioral and biological evolution and may be extended to other fields such as economics, market dynamics and health systems

New Insights about CuO Nanoparticles from Inelastic Neutron Scattering

Inelastic Neutron Scattering (INS) spectroscopy has provided a unique insight into the magnetodymanics of nanoscale copper (II) oxide (CuO). We present evidence for the propagation of magnons in the directions of the ordering vectors of both the commensurate and helically modulated incommensurate antiferromagnetic phases of CuO. The temperature dependency of the magnon spin-wave intensity (in the accessible energy-range of the experiment) conforms to the Bose population of states at low temperatures (T &#8804; 100 K), as expected for bosons, then intensity significantly increases, with maximum at about 225 K (close to TN), and decreases at higher temperatures. The obtained results can be related to gradual softening of the dispersion curves of magnon spin-waves and decreasing the spin gap with temperature approaching TN on heating, and slow dissipation of the short-range dynamic spin correlations at higher temperatures. However, the intensity of the magnon signal was found to be particle size dependent, and increases with decreasing particle size. This &#8220;reverse size effect&#8222; is believed to be related to either creation of single-domain particles at the nanoscale, or &#8220;superferromagnetism effect&#8222; and the formation of collective particle states

Low Temperature Heat Capacity Study of Fe(PO₃)₃ and Fe₂P₂O₇

The heat capacities of two iron phosphates, Fe(PO3)3 and Fe2P2O7, have been measured over the temperature range from (2 to 300) K using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). A phase transition related to magnetic ordering has been found in the heat capacity at T = 8.76 K for Fe(PO3)3 and T = 18.96 K for Fe2P 2O7, which are comparable with literature values from magnetic measurements. by fitting the experimental heat capacity values, the thermodynamic functions, magnetic heat capacities, and magnetic entropies have been determined. Additionally, theoretical fits at low temperatures suggest that Fe2P2O7 has an anisotropic antiferromagnetic contribution to the heat capacity and a large linear term likely caused by oxygen vacancies. Further data fitting in a series over widened temperature regions found that this linear term exists only below 15 K and disappears gradually from (15 to 17) K. © 2013 Published by Elsevier B.V. All rights reserved

Low Temperature Heat Capacity Study of FePO₄ and Fe₃(P₂O₇)₂

The heat capacities of FePO4 and Fe3(P 2O7)2 have been measured using a Quantum Design Physical Property Measurement System (PPMS) over the temperature range from (2 to 300) K. The phase transition due to the Fe3+ magnetic ordering in FePO4 has been determined to occur at T = 25.0 K, which agrees well with magnetic measurements reported in the literature. For Fe3(P 2O7)2, a Schottky anomaly and a four-peak phase transition have been found below 50 K. The thermodynamic functions, magnetic heat capacities, and magnetic entropies of these two compounds have been calculated based on curve fitting of the experimental heat capacity values. The standard molar entropy at T = 298.15 K has been obtained to be (122.21 ± 1.34) J · K-1 · mol-1 and (384.12 ± 4.23) J · K-1 · mol-1 for FePO4 and Fe3(P2O7)2, respectively. All rights reserved

Low Temperature Heat Capacity Study of Fe₃PO₇ and Fe₄(P₂O₇)₃

The low temperature heat capacities of Fe3PO7 and Fe4(P2O7)3 have been measured using a Quantum Design Physical Property Measurement System (PPMS) over the temperature range from (2 to 300) K. Phase transitions due to Fe3+ magnetic ordering have been determined in the heat capacities at temperatures of (164.5 and 47.6) K for Fe3PO7 and Fe4(P 2O7)3, respectively, which agrees well with the magnetic measurements reported in the literature. Also, another small transition occurring at around 27 K for Fe4(P2O 7)3 has been found for the first time. The thermodynamic functions and magnetic heat capacities have been calculated based on the curving fitting of the experimental heat capacity values. Using the fitted heat capacity results, the standard molar entropies have been calculated to be (219.73 ± 2.42) J · K-1 · mol-1 and (561.03 ± 6.17) J · K-1 · mol-1 for Fe3PO7 and Fe4(P2O7) 3, respectively. The calculated magnetic entropy of Fe 3PO7 using the magnetic heat capacity suggests that the five 3d-electrons in the Fe3+ are in the t2g orbital with a low spin state according to crystal field theory. © 2013 Published by Elsevier Ltd

Entropy of Pure-Silica Molecular Sieves

The entropies of a series of pure-silica molecular sieves (structural codes ^*BEA, FAU, MFI, and MTT) are obtained by calorimetric measurements of low-temperature heat capacity. The third-law entropies at 298.15 K are (on the basis of 1 mol of SiO_2):  ^*BEA, 44.91 ± 0.11 J·K^(-1)·mol^(-1); FAU, 44.73 ± 0.11 J·K^(-1)·mol^(-1); MFI, 45.05 ± 0.11 J·K^(-1)·mol^(-1); MTT, 45.69 ± 0.11 J·K^(-1)·mol^(-1); while the corresponding entropies of transition from quartz at 298.15 K are ^*BEA, 3.4 J·K^(-1)·mol^(-1); FAU, 3.2 J·K^(-1)·mol^(-1); MFI, 3.6 J·K^(-1)·mol^(-1); MTT, 4.2 J·K^(-1)·mol^(-1). The entropies span a very narrow range at 3.2−4.2 J·K^(-1)·mol^(-1) above quartz, despite a factor of 2 difference in molar volume. This confirms that there are no significant entropy barriers to transformations between SiO_2 polymorphs. Finally, the Gibbs free energy of transformation with respect to quartz is calculated for eight SiO_2 phases and all are found to be within twice the available thermal energy of each other at 298.15 K