Presence Of Alkaline Earth Metals Research Articles

Advanced solid-phase extraction of tetravalent actinides using a novel hierarchically porous functionalized silica monolith

Separation of actinides is of great concern from the perspective of nuclear energy development and environmental issues, and the development of a highly efficient solid-phase extraction (SPE) process holds significant promise for actinide separation. However, the slow mass transfer kinetics in the currently available SPE separation media limited the throughput and efficiency, rendering the separation process more challenging. Hierarchically porous structures with well-organized and highly interconnected pore systems have been shown to provide efficient mass transfer and enhanced performance in nature. Herein, this paper reports the synthesis of a crack-free diglycolamic acid-functionalized silica monolith with hierarchical macro and meso porous structure for SPE. The hierarchically porous structures were retained upon mild modifications, which favored the convective mass transport and provided more binding sites, resulting in fast kinetics and high throughput. The separation ability was evaluated based on the separation and recovery of Th(IV) from a complex matrix. A superior Th(IV) separation performance (Kd > 2.6 × 104 mL/g) was achieved in the presence of alkaline earth metals, rare earth elements, and uranium within 1 min by batch sorption, and the maximum separation coefficients of Th(IV)/Ln(III) and Th(IV)/U(VI) exceed 1000 and 140, respectively. Particularly, the synthesized material allowed the separation of Th from monazite leachates with highly efficient recovery (> 96%) at a high flow rate (5 mL/min) by column study. Investigation of the binding mechanism revealed the formation of a stable coordination complex (Th(NO3)L3) via Th−O bonds. The material was also employed for the extraction of Pu(IV), and satisfactory sorption was achieved. Thus, this new functionalized material has potential application prospects for an improved actinide separation process.

Sunlight Degradation of the Aminophosphonate Diethylenetriamine Penta-(Methylenephosphonic Acid)

Aminophosphonate diethylenetriamine penta(methylenephosphonic acid) (DTPMP) is a scale inhibitor commonly used in several industries. DTPMP is suspected to cause anthropogenic pollution through discharge into the aquatic environment. DTPMP is assumed to be degraded by sunlight radiation. We recently predicted a preliminary degradation pathway of DTPMP applying UV treatment. Currently, we have not yet evidenced that DTPMP shows the same degradation pattern with natural sunlight. One major reason leads to the fact that the light spectrum emitted by UV lamps does not completely represent the natural sunlight spectrum, and the emitted UVB and UVA irradiation flux is much higher than for solar light. For that reason, the degradation pattern and kinetics might be different between artificial UV treatment and natural sunlight treatment. Here, we investigated whether DTPMP is degradable under natural sunlight radiation, and whether the degradation mechanisms determined through UV treatment are transferable to sunlight. We investigated five different treatment conditions, i.e., DTPMP degradation in direct or diffuse sunlight, in diffuse sunlight with addition of Ca2+ or Mg2+, and in diffuse sunlight with local TW. Our experiment was carried out from March 2021 to October 2021. We performed LC/MS analyses and measured the release of o-PO43−. DTPMP was degraded with all five treatment conditions. The fastest DTPMP degradation occurred in direct and diffuse sunlight without addition of bivalent cations. The addition of Ca2+ and Mg2+ resulted in inhibited degradation. Similar effects occurred for sunlight treatment with local TW. We evidenced different degradation mechanisms for DTPMP depending on the presence of alkaline earth metals as we previously proposed for UV-treated DTPMP. However, both degradation mechanisms of DTPMP belong to the same degradation pathway determined with UV treatment. Therefore, we conclude that DTPMP undergoes a similar degradation pathway in sunlight as compared to UV light.

Structural and impedance spectroscopy study of Mn1.5Y1.5CSr1.5Ba1.5 antiperovskite

The experimental study on temperature and frequency dependent impedance spectroscopy study of an antiperovskite is being reported for the first time in this work as until now only the theoretical studies on dielectric behavior of various antiperovskites have been reported. Additionally, the effect of the presence of alkaline earth metals at A-site on the physical properties of an antiperovskite has been investigated for the first time. The structural and impedance characteristics of Mn1.5Y1.5CSr1.5Ba1.5 antiperovskite, synthesized by mixed oxide method, have been reported in this work. X-Ray Diffraction (XRD) analysis of this antiperovskite indexes it in a cubic crystal system with Ia3‾ space group. The impedance spectroscopy study reveals that the persistent rise in the magnitude of relative dielectric constant (εr) and dielectric loss (tan δ), with increasing temperature, is due to thermally activated charge carriers which results in the surge in conductivity of the sample. The dielectric dispersion in this antiperovskite is ascribed to Maxwell–Wagner form of interfacial polarization that is explained on the basis of Koop's phenomenological theory. The complex impedance analysis signifies a non-Debye relaxation process for this compound.

Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion

Chemical looping with oxygen uncoupling (CLOU), variant to chemical looping combustion (CLC), is working on strategies to transport gaseous oxygen for fuel combustion. The present work reports the process simulation of CLOU of a coal-biomass mixture with CuO oxygen carrier. Variations in the different parameters are compared by replacing pure coal with an equal fraction of coal-biomass mixture. The presence of alkaline earth metals in biomass is seen to increase the coal char conversion in the fuel reactor. The predicted carbon capture efficiency is found to increase with the fuel reactor temperature range of 900 to 965°C irrespective of fuel used. The carbon capture efficiency was also varied with the solids flow rate varying from 3.48 to 13.64 kg/h. The thermal power output for the coal-biomass mixture is further compared with published literature for pure coal in context of its CLOU mode of operation. [Received: March 2, 2018; Accepted: November 26, 2018]

Implications of water hardness in ecotoxicological assessments for water quality regulatory purposes: a case study with the aquatic snail Biomphalaria glabrata (Say, 1818).

Water hardness is a property depending on the presence of alkaline earth metals, mainly calcium and magnesium. Among the strategies for water quality monitoring, ecotoxicological assays are performed to minimize impacts and classify water bodies. For these laboratory evaluations parameters are previously defined in the guidelines, including water hardness for both cultivation and testing medium. The present work was performed to evaluate the effects of different levels of water hardness on the survival and reproduction of the freshwater snail Biomphalaria glabrata and discuss the influence of natural water hardness on the results of ecotoxicological tests with these environmental samples. Comparing the groups it was possible to observe that those maintained in waters with least hardness had lower reproductive success, while the groups maintained in highest hardness showed better reproduction. These data show that waters with low hardness make the reproduction of the snail B. glabrata unfeasible, and this reveal a problem for ecotoxicity assays using natural water samples.

Surface complexation modeling of Uranium(VI) sorption on quartz in the presence and absence of alkaline earth metals

Surface complexation models (SCMs) are widely utilized as a tool to study the mobility of radionuclide to the environment. In this study, two SCMs, electrostatic (ES) and non-electrostatic (NES) models are employed in order to simulate the sorption behavior of U(VI) on quartz in the absence of Mg, Ca, and Sr and ES model in the presence of alkaline earth metals. The surface reaction constants (log K) for ES and NES models were fitted to experimental data by coupling PEST with PHREEQC. The SCM prediction of U(VI) sorption on quartz in the absence of alkaline earth metals is in good agreement with the experimental data in the pH range 6.5–9. The estimated log K values are sensitive to both ES and NES model calculations. In U(VI)-Mg-quartz, U(VI)-Ca-quartz, and U(VI)-Sr-quartz systems, only the ES model shows the general trend of the experimental data. The estimated log K values are sensitive with respect to the surface reactions. Hence, the ES model is more suitable for model calculations of the U(VI)-Mg-quartz, U(VI)-Ca-quartz, and U(VI)-Sr-quartz systems.

Metal ion determination by flame atomic absorption spectrometry through reagentless coacervate phase separation-extraction into lamellar vesicles.

The phase separation of lamellar vesicles of anionic surfactants in aqueous solutions and its application as a novel liquid coacervate extraction procedure was examined. Solutions of lauric acid sodium salt separate into two phases in the presence of alkaline earth metals and a water miscible cosurfactant. It is proven that the surfactant phase is built of a perplexed network of multilamellar vesicles consisting of densely packed bilayers. Several factors affecting the formation of this new phase as well as its analytical utility in the preconcentration of metallic ions were assessed on the basis of better exploitation of this new nonspecific extraction technique. In essence, although the procedure to arrive at the optimum conditions seems laborious, the delivered method is straightforward, alleviating the requirement for prereaction with a complexing agent and highly reproducible under the optimum experimental conditions. As an analytical demonstration, the method was successfully applied to the determination of Cd(2+) and Zn(2+) in natural waters. Recoveries were higher than 95%, and detection limits as low as 3 microg L(-)(1) were accomplished by preconcentrating only 10 mL of sample volume in the presence of 0.45% (w/v) anionic surfactant.

CO 2 reforming of CH 4 over Ni/perovskite catalysts prepared by solid phase crystallization method

Ni-supported catalysts on perovskite-type oxides have been prepared by “solid phase crystallization” ( spc) method and tested for CO 2 reforming of CH 4 into synthesis gas at 850°C. The Ni catalysts were obtained in situ during the reaction from the oxides as the precursors in which nickel species were homogeneously incorporated in the perovskite structure. Ni/Ca 0.8Sr 0.2TiO 3 and Ni/BaTiO 3 catalysts showed high activity as well as high sustainability among the catalysts tested. The high activity may be due to highly dispersed and stable Ni metal particles (diameter<1 nm) on the perovskite, where the nickel species thermally evolve from the cations homogeneously distributed in an inert perovskite matrix as the precursors during the reaction. Nickel species was partly incorporated in the perovskite structure by replacing the Ti site and partly separated as NiO from the structure after the calcination of the precursors, and the former species likely affords the highly dispersed Ni metal under the reducing atmosphere. The amount of NiO detected by XRD analyses was smaller on BaTiO 3 than on Ca 0.8Sr 0.2TiO 3, while that of surface Ni obtained by TGA was larger on Ca 0.8Sr 0.2TiO 3 than on BaTiO 3. It is thus likely that an incorporation of Ni was enhanced in BaTiO 3 compared to Ca 0.8Sr 0.2TiO 3, resulting in the higher dispersion of Ni metal particles on the former support. This well coincided with the activity of Ni/BaTiO 3 being higher than that of Ni/Ca 0.8Sr 0.2TiO 3 at high space velocity. The high sustainability against coke formation may be partly due to the mobile oxygen as well as due to the presence of alkaline earth metals in the perovskite supports. Oxygen mobility in the perovskite was further tested by CO 2 pulse reactions, suggesting an easy migration of oxygen over the perovskite structure. It is most likely that the oxygen easily migrates from the supports to the surface of fine Ni particles, where the coke material can be oxidized into carbon oxides.

Simultaneous determination of uranium and thorium with Arsenazo III by second-derivative spectrophotometry

A derivative spectrophotometric method has been developed for the simultaneous determination of microgram quantities of uranium and thorium with Arsenazo III in hydrochloric acid medium. The second-derivative absorbances of the uranium and thorium Arsenazo III complexes at 679.5 and 684.4 nm are used for their quantification. Uranium and thorium, both in the range 0.1–0.7 μg/ml have been determined simultaneously with good precision. The procedure does not require separation of uranium and thorium, and allows the determination of both metals in the presence of alkaline-earth metals and zirconium, but lanthanides interfere.