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Liquid–Liquid Separation by Supramolecular Systems
Published in Bruce A. Moyer, Ion Exchange and Solvent Extraction: Volume 23, 2019
Gabriela I. Vargas-Zúñiga, Qing He, Jonathan L. Sessler
Ions are particles that exist as positively or negatively charged species—anions and cations. These particles can be monoatomic or polyatomic (e.g., Na+, F−, or NH4+, [Pu(NO3)6]2−). Many of these ions play important roles in biological and industrial processes. For example, iodide and bicarbonate are involved in the biosynthesis of hormones and pH regulation, respectively.1 Other entities of physiological interest, such as polypeptides, proteins, nucleic acids, or metal cations coordinated to enzymes, are complex ions that participate in essential life processes.2 In metallurgy, metals are usually won from naturally occurring salts via what are often complex purification and processing sequences. Oxyanions, such as sulfate and nitrate, are components in acid rain, whereas phosphates and nitrates used in fertilizers can lead to the eutrophication of lakes and other waterways.3 Actinide, lanthanide, and other metallic salts are important constituents of radioactive tank waste.4 Zwitterions, such as amino acids, are charged species capable of existing as anions, cations, or net neutral entities depending on the pH of the medium.2
The evaluation of oxide scale formation during hot corrosion of Rene-80 superalloy under thermal shock at different dwell times
Published in Corrosion Engineering, Science and Technology, 2022
Arman Rabieifar, M.Reza Afshar, Hamidreza Najafi, Said Nategh
The ‘fluxing-re-precipitation’ mechanism proposed by Rapp and Goto [22] is considered an acceptable mechanism for hot corrosion. According to this mechanism, the protective efficiency of oxide scales is reduced due to their contact with molten salt. In fact, during the contact of the oxide scale with the salt, the oxide dissolves in the salt. If this dissolution is due to the combination of the oxide with the O2– ion (oxyanion ion), it is known as ‘basic fluxing.’ However, if it is due to the decomposition of the oxide into cations and O2–, it is known as ‘acidic fluxing.’ Owing to the negative gradient of oxyanion ions concentration in the molten salt layer, oxides re-precipitate again as separate particles at the molten salt layer/atmosphere interface [15,16,21].
Synthesis and characterization of magnetic graphene oxide for arsenic removal from aqueous solution
Published in Environmental Technology, 2018
A. I. A. Sherlala, A. A. A. Raman, M. M. Bello
The adsorption of the As(III) occurs mainly through surface complexation between the functional groups on the surface of the MGO and the As(III) (Figure 10). In general, the adsorption occurs when arsenic oxyanion complexes with surface –OH or –OH2 groups that are coordinated to Fe3+[25]. The adsorption occurs predominantly via monodentate complex formation, where a single oxygen atom from the oxyanion coordinates a single Fe3+ at the surface of the oxide. However, the formation of an outer-sphere complex where the cation is bound to the surface of –OH or –OH2 through hydrogen bonding has also been observed [25]. This proposed mechanism is supported by the FTIR analysis as discussed in Section 3.1.3. Thus, surface complexation is the governing mechanism of As(III) adsorption using MGO [37,38]. Although it is widely reported that As(III) removal is controlled by the surface complexation, the precise nature of the mechanism is still being discussed [4].
Effect of HEH[EHP] impurities on the ALSEP solvent extraction process
Published in Solvent Extraction and Ion Exchange, 2018
Vanessa E Holfeltz, Emily L. Campbell, Dean R. Peterman, Robert F. Standaert, Alena Paulenova, Gregg J. Lumetta, Tatiana G Levitskaia
The results of extraction/scrub/strip tests using ALSEP solvent prepared with purified HEH[EHP] indicated that acidic impurities contribute to the Am(III) retention during stripping. A masking agent was selected to complex acidic impurities in the organic phase, in order to evaluate the DAm values under these conditions. Trioctylamine (TOA) is an organic base, and as such, reacts with a phosphorus oxyacid to form a lipophilic ion pair containing the trioctylammonium cation and the phosphorus oxyanion. Additionally, TOA has been reported to form complexes with organic acids in various organic diluents.[27–30] TOA (10 mM) was therefore added to four ALSEP solvent samples prepared with HEH[EHP] from suppliers A-1, A-2 and B, used either as received (unpurified) or purified by the third phase method.[13] The solvents were subjected only to extraction and stripping steps for this test, and single replicates were performed. The extraction and strip DAm values were determined as described previously.