{"title":"Sorption of Sr(II) Ions with Tricalcium Phosphate in the Presence of Humic Acids","authors":"A. A. Ioshin, I. V. Volkov, E. V. Polyakov","doi":"10.1134/s1066362223060073","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The sorption behavior of traces Sr(II) toward β-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> (TCP) depending on the concentration of the cation, pH, and concentrations of humic acids (HA) in the solution was studied. Thermodynamic analysis of the solubility of TCP (<b>1</b>) was performed taking into account the formation of Ca(OH)<sub>2</sub> (CH, <b>2</b>), Ca(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub> (MCPA, <b>3</b>), CaHPO<sub>4</sub>·2H<sub>2</sub>O (DCPD, <b>4</b>), Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH (hydroxyapatite, OHAp, <b>5</b>), and Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> (DCPP, <b>6</b>). It was shown that, depending on the pH of the solution, the main equilibrium phases with the solution are phases <b>4</b> and <b>5</b>. X-ray diffraction analysis, Raman spectroscopy, and <sup>31</sup>P NMR data of the phase (<b>1</b>) samples after contact with a solution of 0.01 M NaNO<sub>3</sub> for about 10 days showed the presence of only the phase <b>1</b>. The solubility of <b>1</b> regarding the concentration of Ca<sup>2+</sup>, PO<sub>4</sub><sup>3–</sup> ions and the stoichiometric ratio (Ca/P) in solutions, depending on pH, correspond to the presence of surface phases <b>4</b> or <b>5</b>. The model of surface complexation in the Henry region adequately describes the mechanism of Sr(II) sorption by the surface phase <b>5</b> on TCP particles in the form of the SrHPO<sub>4</sub><sup>0</sup> complex. The formation of the HA complex of Sr(II) in solution does not affect distribution coefficient <i>K</i><sub>d</sub>(Sr) in the range of HA concentrations of 0–150 mg/L due to the competitive effect of hydrogen phosphate ions on strontium complexes.</p>","PeriodicalId":747,"journal":{"name":"Radiochemistry","volume":null,"pages":null},"PeriodicalIF":0.9000,"publicationDate":"2024-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Radiochemistry","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1134/s1066362223060073","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
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Abstract
The sorption behavior of traces Sr(II) toward β-Ca3(PO4)2 (TCP) depending on the concentration of the cation, pH, and concentrations of humic acids (HA) in the solution was studied. Thermodynamic analysis of the solubility of TCP (1) was performed taking into account the formation of Ca(OH)2 (CH, 2), Ca(H2PO4)2 (MCPA, 3), CaHPO4·2H2O (DCPD, 4), Ca5(PO4)3OH (hydroxyapatite, OHAp, 5), and Ca2P2O7 (DCPP, 6). It was shown that, depending on the pH of the solution, the main equilibrium phases with the solution are phases 4 and 5. X-ray diffraction analysis, Raman spectroscopy, and 31P NMR data of the phase (1) samples after contact with a solution of 0.01 M NaNO3 for about 10 days showed the presence of only the phase 1. The solubility of 1 regarding the concentration of Ca2+, PO43– ions and the stoichiometric ratio (Ca/P) in solutions, depending on pH, correspond to the presence of surface phases 4 or 5. The model of surface complexation in the Henry region adequately describes the mechanism of Sr(II) sorption by the surface phase 5 on TCP particles in the form of the SrHPO40 complex. The formation of the HA complex of Sr(II) in solution does not affect distribution coefficient Kd(Sr) in the range of HA concentrations of 0–150 mg/L due to the competitive effect of hydrogen phosphate ions on strontium complexes.
期刊介绍：
Radiochemistry is a journal that covers the theoretical and applied aspects of radiochemistry, including basic nuclear physical properties of radionuclides; chemistry of radioactive elements and their compounds; the occurrence and behavior of natural and artificial radionuclides in the environment; nuclear fuel cycle; radiochemical analysis methods and devices; production and isolation of radionuclides, synthesis of labeled compounds, new applications of radioactive tracers; radiochemical aspects of nuclear medicine; radiation chemistry and after-effects of nuclear transformations.
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