Kinetics and mechanism of radium-isotopes dissolution in TENORM scale waste associated with petroleum production using c
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RESEARCH ARTICLE
Kinetics and mechanism of radium-isotopes dissolution in TENORM scale waste associated with petroleum production using certain organic carbon source: lactic acid solution—case study Elsayed M. El Afifi 1 & Ahmed M. Shahr El-Din 1 & Moustafa A. Hilal 1 Received: 14 March 2020 / Accepted: 23 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The present study is conducted to explore the dissolution as inferred from the kinetic mechanism for radium-isotopes (228Ra, 226Ra, and 224 Ra) in the TENORM scale waste deposited in oilfield pipes and equipment, Gulf of Suez, Egypt. The main efficiency factors for Ra2+-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 Ra2+-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 Ra2+-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 (Ea) of the leaching process was 10.51 kJ mol−1. This value conforms that the leaching process for removal of Ra2+-isotopes in the TENORM scale waste by LA solution is controlled by a diffusion process. Values of thermodynamic parameters (ΔGo, ΔHo, ΔSo) were determined and indicate that dissolution of Ra2+-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 Ra2+-species and/or these due conversions of insoluble Ra-sulfate to more soluble Ra-sulfide and/or Ra-hydrogen sulfide by LA solutions. Keywords Strategic industries . TENORM wastes . Ra-isotopes . Treatment . Organic reagents
Introduction The enhanced natural radioactivity in the oil and gas production was identified at the beginning of the last century. It is found that elevated levels of radium-isotopes (228Ra, 226Ra, 224 Ra, and 223Ra) and lead-210 started to be observed when scrap metal dealers would detect unacceptably high levels of natural radioactivity from oilfield equipment (McLennan 1904; Zielinski and Otton 1999; El Afifi 2001). The technically enhanced naturally occurring radioactive material Responsible editor: Philippe Garrigues * Elsayed M. El Afifi [email protected]; [email protected] 1
Analytical Chemistry and Control Department, Hot Laboratories and Waste Management Center (HLWMC), Egyptian Atomic Energy Authority (EAEA), Cairo Post Code No. 13759, Egypt
(TENORM) found in high activity concentrations in the waste streams associated with petroleum exploration (El Afifi et al. 2004; Al-Saleh and Al-Harshan 2008). The TENORM wastes were categorized to scale,
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