scholarly journals Thermodynamic Studies on the Sorption of Lead (II), Chromium (III) and Manganese (II) ions onto Acid-Activated Shale

2021 ◽  
Vol 2 ◽  
pp. 10-18
Author(s):  
I. R. Ilaboya ◽  
J. S. Okpoko
Keyword(s):  
Metal Ions ◽  
Active Site ◽  
Effect Of Temperature ◽  
Adsorption Parameters ◽  
X Ray ◽  
Solution Interface ◽  
Varied Temperature ◽  
Adsorption Temperature ◽  
Endothermic Process ◽  
Higher Temperature

Shale mineral in its raw form was collected, processed, calcinated and activated using tetraoxosulphate (VI) acid. The microstructural arrangement and chemical composition of the raw, calcinated and acid-activated shale was determined using x-ray fluorescence and scanning electron microscope to verify its ability for the removal of Pb2+, Cr3+ and Mn2+ from wastewater. Batch experimental method was used to study the effect of different adsorption parameters on the sorption efficiency of shale. The effect of temperature on the sorption of Pb2+, Cr3+ and Mn2+ on acid-activated shale was investigated at varied temperature of 15 – 40 . The calculated value of enthalpy () was 12.50 kJ/mol for Pb2+ adsorption, 5 kJ/mol for Cr3+ and 11 kJ/mol for Mn2+ adsorption. The calculated values of Gibbs free energy () varies from -6.576 kJ/mol to 1.358 kJ/mol for Pb2+ adsorptions, from -2.696 kJ/mol to 0.192 kJ/mol for Cr3+ adsorptions, and -4.994 kJ/mol to 1.870 kJ/mol for Mn2+ adsorptions. The entropy () range is 38.68 – 60.946 kJ/mol for Pb2+ adsorptions, 16.69 – 24.58 kJ/mol for Cr3+ adsorptions, and 31.70 – 51.10 kJ/mol for Mn2+ adsorptions. The positive value of  shows that the adsorption of Pb2+, Cr3+ and Mn2+ onto acid-activated shale was an endothermic process. The values of  are negative at temperature of 298 K and above for the three metal ions studied, which confirmed that the adsorption of Pb2+, Cr3+ and Mn2+ on acid-activated shale was a spontaneous process. The decline in  with increasing adsorption temperature showed that adsorptions of Pb2+, Cr3+ and Mn2+ onto acid-activated shale became better at higher temperature while the positive value of  for all metal ions studied showed the amplified arbitrariness at the solid-solution interface during the fixation of the adsorbate on the active site of acid-activated shale.

scholarly journals Adsorption Parameters and Superficial Species in the Nickel-Alumina System

1987 ◽  
Vol 4 (3) ◽  
pp. 162-175 ◽  
Author(s):  
Raúl A.E. Rodriguez ◽  
Carmen V. Caceres ◽  
Blanco Blanco ◽  
Horacio J. Tomas
Keyword(s):  
Photoelectron Spectroscopy ◽  
Thin Layers ◽  
Nickel Nitrate ◽  
X Ray Diffraction ◽  
Adsorption Parameters ◽  
X Ray ◽  
Adsorption Sites ◽  
Adsorption Temperature ◽  
Nickel Species ◽  
Nitrate Solutions

The equilibrium adsorption of nickel on γ-alumina was studied at 293 and 333 K. Nickel nitrate solutions in the range 0.1 - 2% (w/v, expressed as NiO) were used. Both the equilibrium constant and the number of adsorption sites increased with the adsorption temperature. Adsorption and desorption rate constants were estimated by fitting a theoretical model to the profiles obtained by impregnation of γ-alumina thin layers with nickel nitrate solutions. Representative solid samples differing in nickel contents were studied along both isotherms by X-ray diffraction, diffuse reflectance and X-ray photoelectron spectroscopy. It is concluded that, in the composition range studied, nickel forms a partially inverted spinel (NiAl2O4); the degree of inversion being greater in the samples prepared at 293 K than in those corresponding to 333 K. Also, the dispersion of nickel species is constant for each adsorption temperature.

scholarly journals A Tryptophan ‘Gate’ in the CRISPR-Cas3 Nuclease Controls ssDNA Entry into the Nuclease Site, That When Removed Results in Nuclease Hyperactivity

2021 ◽  
Vol 22 (6) ◽  
pp. 2848
Author(s):  
Liu He ◽  
Zoe Jelić Matošević ◽  
Damjan Mitić ◽  
Dora Markulin ◽  
Tom Killelea ◽  
...  
Keyword(s):  
Active Site ◽  
Nuclease Activity ◽  
Human Cells ◽  
Effect Of Temperature ◽  
Tryptophan Residue ◽  
Allosteric Control ◽  
Class 1 ◽  
Higher Temperature ◽  
Dynamics Simulations ◽  
Induced Changes

Cas3 is a ssDNA-targeting nuclease-helicase essential for class 1 prokaryotic CRISPR immunity systems, which has been utilized for genome editing in human cells. Cas3-DNA crystal structures show that ssDNA follows a pathway from helicase domains into a HD-nuclease active site, requiring protein conformational flexibility during DNA translocation. In genetic studies, we had noted that the efficacy of Cas3 in CRISPR immunity was drastically reduced when temperature was increased from 30 °C to 37 °C, caused by an unknown mechanism. Here, using E. coli Cas3 proteins, we show that reduced nuclease activity at higher temperature corresponds with measurable changes in protein structure. This effect of temperature on Cas3 was alleviated by changing a single highly conserved tryptophan residue (Trp-406) into an alanine. This Cas3W406A protein is a hyperactive nuclease that functions independently from temperature and from the interference effector module Cascade. Trp-406 is situated at the interface of Cas3 HD and RecA1 domains that is important for maneuvering DNA into the nuclease active site. Molecular dynamics simulations based on the experimental data showed temperature-induced changes in positioning of Trp-406 that either blocked or cleared the ssDNA pathway. We propose that Trp-406 forms a ‘gate’ for controlling Cas3 nuclease activity via access of ssDNA to the nuclease active site. The effect of temperature in these experiments may indicate allosteric control of Cas3 nuclease activity caused by changes in protein conformations. The hyperactive Cas3W406A protein may offer improved Cas3-based genetic editing in human cells.

scholarly journals Effect of Temperature on Strain-Induced Hardness of Lead-Free Solder Wire using Nanoindentation Approach

2020 ◽  
Vol 49 (12) ◽  
pp. 3019-3026
Author(s):  
Norliza Ismail ◽  
Maria Abu Bakar ◽  
Saiful Bahari Bakarudin
Keyword(s):  
Tensile Test ◽  
Room Temperature ◽  
Constant Strain Rate ◽  
Effect Of Temperature ◽  
Sac305 Solder ◽  
Varied Temperature ◽  
Higher Temperature ◽  
Free Solder ◽  
Hardness Values ◽  
Initial Cycle

Hardness properties of SAC305 solder wire under tensile test at varied temperature was investigated. Continuous multi-cycle (CMC) nanoindentation technique with ten cycle of indentation for each sample was performed to evaluate the hardness behaviour of SAC305 solder wire at different depth of indentation. As a result, all investigated SAC305 solder wire under constant strain rate of tensile test and at different temperature revealed the occurrence of indentation size effect (ISE). At initial cycle of indentation, SAC305 solder wire at room temperature (25 °C) have higher hardness value compared to the others sample which exposed to the varied temperature during tensile test. Besides, higher temperature causes the higher strain or elongation to the SAC305 solder wire. Applied of strain during the tensile test had generated the pre-dislocation activity in the SAC305 solder wire. Therefore, higher hardness values of SAC305 at room temperature is due to the existence of high dislocation density induced by the applied strain. Nevertheless, the existence of heat at 60, 90, 120 and 180 °C during the tensile test prompt the rearrangement of dislocation and reduce the dislocation activities, thus, allowing higher elongation of solder wire.

scholarly journals Binding of Mn-deoxyribonucleoside triphosphates to the active site of the DNA polymerase of bacteriophage T7

2011 ◽  
Vol 26 (2) ◽  
pp. 159-162 ◽  
Author(s):  
Barak Akabayov ◽  
Charles C. Richardson
Keyword(s):  
Metal Ions ◽  
Dna Polymerase ◽  
Active Site ◽  
Divalent Metal ◽  
Enzymatic Activities ◽  
Bacteriophage T7 ◽  
Divalent Metal Ions ◽  
X Ray ◽  
Full Activity

Divalent metal ions are crucial as cofactors for a variety of intracellular enzymatic activities. Mg2+, as an example, mediates binding of deoxyribonucleoside 5′-triphosphates followed by their hydrolysis in the active site of DNA polymerase. It is difficult to study the binding of Mg2+ to an active site because Mg2+ is spectroscopically silent and Mg2+ binds with low affinity to the active site of an enzyme. Therefore, we substituted Mg2+ with Mn2+:Mn2+ that is not only visible spectroscopically but also provides full activity of the DNA polymerase of bacteriophage T7. In order to demonstrate that the majority of Mn2+ is bound to the enzyme, we have applied site-directed titration analysis of T7 DNA polymerase using X-ray near edge spectroscopy. Here we show how X-ray near edge spectroscopy can be used to distinguish between signal originating from Mn2+ that is free in solution and Mn2+ bound to the active site of T7 DNA polymerase. This method can be applied to other enzymes that use divalent metal ions as a cofactor.

The Effect of Temperature and Time on the Formation of TiO2 (B) Nanowires via Hydrothermal Method

2018 ◽  
Vol 280 ◽  
pp. 15-20
Author(s):  
Thida San Nwe ◽  
Matthana Khangkhamano ◽  
Lek Sikong ◽  
Kalayanee Kooptanond
Keyword(s):  
Phase Composition ◽  
Reaction Time ◽  
Hydrothermal Synthesis ◽  
Effect Of Temperature ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
Hydrothermal Temperature ◽  
X Ray ◽  
Higher Temperature ◽  
Scanning Electron

TiO2(B) nanowires were prepared at 170 °C, 200 °C and 220 °C for 24 h via hydrothermal synthesis to evaluate the effect of temperature on phase composition and morphologies. The effect of reaction time: 24 and 72 h on the formation was also studied at 170 °C. All samples were calcined in air at 400 °C for 2 h. Phase identification was performed using X-ray diffraction (XRD) and morphologies was examined by a scanning electron microscope (SEM). It was found that hydrothermal temperature and time played an important role in defining TiO2phase composition and its morphology. For 24 h hydrothermal synthesis, at low temperature of 170 °C, anatase TiO2nanoparticles were formed, while at higher temperature of 200 and 220 °C, TiO2(B) nanowires with averaged diameter of 49 nm and several micrometers in length were produced. Interestingly at 170 °C, by increasing reaction time to 72 h, anatase TiO2nanoparticles were completely transformed to TiO2(B) nanowires with averaged diameter of 74 nm and 2-4 micrometers in length.

Effect of Temperature on La1.85Sr0.15CuO4 Single Crystal Growth by Floating Zone Method

2007 ◽  
Vol 546-549 ◽  
pp. 1897-1900 ◽  
Author(s):  
X.Q. Xiang ◽  
J.F. Qu ◽  
Y.Q. Zhang ◽  
X.L. Lu ◽  
X.G. Li
Keyword(s):  
Crystal Growth ◽  
Single Crystal ◽  
Effect Of Temperature ◽  
Superconducting Transition ◽  
Floating Zone ◽  
X Ray Diffraction ◽  
Zone Method ◽  
Floating Zone Method ◽  
X Ray ◽  
Higher Temperature

Superconducting single crystals of La1.85Sr0.15CuO4 have been grown at various temperatures without single crystal seeds by the traveling-solvent floating-zone method. In order to avoid the formation of bubbles during the crystal growth process, a flowing atmosphere of 2 atm oxygen or 1 atm air was applied in different temperature range. It was found that the crystal quality could be improved by raising the growth temperature in a certain range, and the orientation changed from (110) to (100) at higher temperature. X-ray diffraction results showed that the full-width at half-maximum of the best as-prepared crystal was 0.086°. The crystals grown in 2 atm oxygen showed a superconducting transition temperature (Tc) of 37.3 K, while the crystals grown in floating air showed a Tc of about 35 K and it could be improved to 36.5 K by annealing in flowing oxygen.

Adsorption of iron(III), cobalt(II), and nickel(II) on activated carbon derived from Xanthoceras Sorbifolia Bunge hull: mechanisms, kinetics and influencing parameters

2017 ◽  
Vol 75 (8) ◽  
pp. 1849-1861 ◽  
Author(s):  
Xiaotao Zhang ◽  
Yinan Hao ◽  
Ximing Wang ◽  
Zhangjing Chen
Keyword(s):  
Activated Carbon ◽  
Iron Group ◽  
Adsorption Parameters ◽  
X Ray ◽  
Adsorption Capacities ◽  
Adsorption Temperature ◽  
Monolayer Adsorption ◽  
Pseudo Second Order ◽  
Adsorption Desorption ◽  
Kinetics And Isotherms

Xanthoceras Sorbifolia Bunge hull activated carbon (XSA) was prepared and characterized by Brunauer–Emmett–Teller analysis, scanning electron microscopy and energy dispersive X-ray (EDX) spectroscopy. The ability of XSA as an adsorbent was investigated for the removal of the iron group ions Fe(III), Co(II), and Ni(II) from aqueous solution. Optimum adsorption parameters were determined based on the initial concentrations of the iron group ions, pH, adsorption temperature, and adsorption time in adsorption studies. The maximum monolayer adsorption capacities were 241.13 mg/g for Fe(III), 126.05 mg/g for Co(II), and 187.96 mg/g for Ni(II), respectively. Adsorption kinetics and isotherms showed that the adsorption process best fitted the nonlinear pseudo-second-order and Langmuir models, and the affinity of the ions for XSA decreased as follows: Fe(III) > Ni(II) > Co(II). Regeneration studies indicated that XSA could be used after several consecutive adsorption/desorption cycles using HNO3. Fourier transform infrared and EDX spectra revealed the chemical adsorption value of XSA as an adsorbent for removing iron group ions from aqueous solutions.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

Application of In Situ X-ray Absorption Spectroscopy to Study Dilute Chromium Ions in a Molten Chloride Salt

2019 ◽  
Author(s):  
Jisue Moon ◽  
Carter Abney ◽  
Dmitriy Dolzhnikov ◽  
James M. Kurley ◽  
Kevin A. Beyer ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Structure ◽  
Chloride Salt ◽  
X Ray ◽  
Molten Chloride ◽  
Stable Species ◽  
Higher Temperature ◽  
Cr Concentration ◽  
X Ray Absorption

The local structure of dilute CrCl<sub>3</sub> in a molten MgCl<sub>2</sub>:KCl salt was investigated by <i>in situ</i> x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800<sup>o</sup>C. This constitutes the first experiment where dilute Cr speciation is explored in a molten chloride salt, ostensibly due to the compounding challenges arising from a low Cr concentration in a matrix of heavy absorbers at extreme temperatures. CrCl<sub>3</sub> was confirmed to be the stable species between 200 and 500<sup>o</sup>C, while mobility of metal ions at higher temperature (>700<sup>o</sup>C) prevented confirmation of the local structure.

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