Dissolution of [ 226 Ra]BaSO 4 and partial separation of 226 Ra from radium/barium sulfate: A new treatment method for NORM waste from petroleum industry

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

The present study is conducted to explore the dissolution as inferred from the kinetic mechanism for radium-isotopes (²²⁸Ra, ²²⁶Ra, and ²²⁴Ra) 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 (E_a) 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 (∆G^o, ∆H^o, ∆S^o) 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.

An Efficient Radiochemical Method for Extraction of 226Ra From the Soil Samples

Background: Radium-226 is a radioactive element, with a very long half-life of 1600 years, producing radon gas. According to the United States Environmental Protection Agency, radon gas is the second most important factor causing lung cancer. Objectives: The purpose of this study was to separate 226Ra from the soil of high background radiation area by a radiochemical method for using in radon calibration chamber. Methods: 226Ra can be used in standard calibration chambers for calibration of radon detection systems. For this purpose, radiochemical method was used to extract radium from the soil with a high concentration of 226Ra. Four soil samples used in this study were selected from high background radiation areas of Ramsar, north of Iran. Equal amounts of samples were gathered from each region and ground. The specific activity of radium-226 was measured with HPGe detector. The highest specific activity of radium-226 (44.8 Bq/g) belonged to Talesh-Mahaleh. After radiochemical separation of 226Ra, the specific activity of extracted radium crystals was measured with the HPGe detector. Results: According to the results, the specific activity of 226Ra was found to be 94.97 Bq/g. Therefore, the specific activity of 226Ra was 2.12 times greater in the extracted crystals than in the original soil samples. Conclusion: The results indicate that using the radiochemical method proposed in this study, 226Ra can be extracted with an efficiency of 42%

Preliminary investigations on reducing the high radiation risk level of TENORM scale waste from petroleum industry

The main objective of this study is directed to remove 226Ra, 228Ra radionuclides from TENORM scale waste without seriously degradation the physicochemical characteristics of soils or generating waste. It was found that 82, 87% removal of total radioactivity using successive washing by commercial and TX-100 solutions, respectively, after seven cycles. Some radiation risk before and after treatment with surfactants were determined. It is a promising and efficient as well as economic process. Our results from this task could provide a useful information for defining the establishing and operating on a pilot-scale plant for efficient and economic TENORM treatment.

Chemical fractionation of radium-226 in NORM contaminated soil from oilfields

Contamination of soil with ²²⁶Ra is a common problem in the oilfields, leading to costly remediation and disposal programmes. The present study focuses on the chemical fractionation and mobility of ²²⁶Ra in contaminated soils collected from an oilfield using a three-step sequential extraction procedure (BCR). The total activity concentrations of ²²⁶Ra in contaminated soils were measured and found to be in the range from 1030 ± 90 to 7780 ± 530 Bq kg^-1, with a mean activity concentration of 2840 ± 1840 Bq kg^-1. The correlation between the total concentration of ²²⁶Ra and soil properties, mainly pH, LOI, C_org, clay and Ca, was investigated using the principal component analysis method (PCA). The chemical fractionation of ²²⁶Ra was studied using the sequential extraction method (BCR). The highest fraction of ²²⁶Ra (27-65%) was found to be in the acid-reducible fraction, which suggests that ²²⁶Ra is mainly bound to FeMn oxides. The BCR method showed that high percentages of ²²⁶Ra were found to be in mobile soil phases (between 45 and 99%). Consequently, groundwater contamination could occur due to the remobilization of ²²⁶Ra from soils under normal environmental conditions. However, the obtained results could be useful to reduce the volume of NORM wastes generated from the oilfields and decision-making process for final treatment and disposal of NORM-contaminated soil.