| Autor: |
El Afifi EM; Analytical Chemistry and Control Department, Hot Laboratories and Waste Management Center (HLWMC), Egyptian Atomic Energy Authority (EAEA), Cairo, Post Code No. 13759, Egypt. em_afifi1968@yahoo.com., Shahr El-Din AM; Analytical Chemistry and Control Department, Hot Laboratories and Waste Management Center (HLWMC), Egyptian Atomic Energy Authority (EAEA), Cairo, Post Code No. 13759, Egypt., Hilal MA; Analytical Chemistry and Control Department, Hot Laboratories and Waste Management Center (HLWMC), Egyptian Atomic Energy Authority (EAEA), Cairo, Post Code No. 13759, Egypt. |
| Jazyk: |
angličtina |
| Zdroj: |
Environmental science and pollution research international [Environ Sci Pollut Res Int] 2020 Oct; Vol. 27 (30), pp. 38134-38147. Date of Electronic Publication: 2020 Jul 03. |
| DOI: |
10.1007/s11356-020-09863-1 |
| Abstrakt: |
The present study is conducted to explore the dissolution as inferred from the kinetic mechanism for radium-isotopes ( 228 Ra, 226 Ra, and 224 Ra) in the TENORM scale waste deposited in oilfield pipes and equipment, Gulf of Suez, Egypt. The main efficiency factors for Ra 2+ -compound dissolution by lactic acid (LA) solution, e.g., reactive organic carbon (i.e., electron-donor source), have been investigated, and optimum chemical conditions have been determined. The obtained data were also employed to predict the leaching kinetics and mechanism of the Ra 2+ -isotopes removal by three shrinking core models (SCM, liquid film process-chemical controlled process-diffusion controlled process) and Arrhenius model. The maximum leaching percentage of Ra 2+ -isotopes reached to 55-60% at the optimal leaching conditions (0.3 M LA, 5 h, 25 °C, ϕ < 1 mm, S/L ratio 10/50 g mL -1 ). The Ra-isotopes removal proceeds kinetically by diffusion-controlled process. Activation energy (E a ) of the leaching process was 10.51 kJ mol -1 . This value conforms that the leaching process for removal of Ra 2+ -isotopes in the TENORM scale waste by LA solution is controlled by a diffusion process. Values of thermodynamic parameters (∆G o , ∆H o , ∆S o ) were determined and indicate that dissolution of Ra 2+ -isotopes in the studied waste is non-spontaneous and temperature dependent. Moreover, the leaching mechanism may be attributed to the dissolution of soluble exchangeable and acidic species of Ra 2+ -species and/or these due conversions of insoluble Ra-sulfate to more soluble Ra-sulfide and/or Ra-hydrogen sulfide by LA solutions. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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