The effects of pH on U(VI)/Th(IV) and Ra(II)/Ba(II) adsorption by polystyrene-nano manganese dioxide composites: Fourier Transform Infra-Red spectroscopic analysis.

Fourier Transform Infra-Red (FTIR) spectroscopy provides structural information of prime importance to understand ions coordination to adsorbents. This consequently aids in the design of improved ion exchange materials and help in deriving the optimum adsorption conditions. In the present work, the adsorption mechanism of both U(VI)/Th(IV) and Ra(II)/Ba(II) radionuclides couples onto polystyrene-nano manganese dioxide (PS-NMO) composite is reported in relation to the effect of working solution pH. The separation of each radionuclide couple; i.e. U(VI)/Th(IV) and Ra(II)/Ba(II); could be effectively achieved at pH = 3 and pH = 1 respectively. The pH values not only determine the species of the respected elements that are mainly present in aqueous solution before applying the adsorbent, but it also alters the structure of the composite adsorbent. FTIR spectroscopy showed that Th(IV) formed inner sphere complexes and occupied the A site in the dioxide layer, while U(VI) formed outer sphere complexes on the surface of the composite. Spectra subtraction showed that some aromatic bands and vinyl C-H bands were split or shifted to lower wavenumbers with the loading of Ba(II). This was attributed to changes in the composite stereochemistry to accommodate Ba(II). The working solution pH could be the key in the separation process of both U(VI)/Th(IV) and Ra(II)/Ba(II) from their mixture, and FTIR spectroscopy stands as a useful technique to explain the difference between metal ions responses to adsorbants.

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, Corg, 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.

Dissolution of [²²6Ra]BaSO4 and partial separation of ²²6Ra from radium/barium sulfate: A new treatment method for NORM waste from petroleum industry.

Complete dissolution of [(226)Ra]BaSO4 precipitate was successfully performed using NaNO2 as a reducing agent in acidic solution at room temperature. Results showed a significant effect of acid and NaNO2 concentrations and temperature on the dissolution efficiency. The method was successfully used for separation of radium from NORM scale samples from the petroleum industry; sufficient volume reduction of NORM waste was achieved. The obtained (226)Ra solution was purified using two separation methods. The dissolution method can be of great interest in the development of radiochemical analysis of radium isotopes.

Characterization of NORM solid waste produced from the petroleum industry.

The accumulation of scales in the production pipe lines is a common problem in the oil industry, reducing fluid flow and leading to costly remediation and disposal programmes. Thus, an accurate determination of the activity of the radionuclides in scale samples is essential for environmental protection. The present study focuses on the characterization of naturally occurring radioactive materials (NORM) in scales generated from the petroleum industry to develop a suitable NORM waste management plan. The activity concentrations of 226Ra, 228Ra and 210Pb in 32 representative samples, collected from a number of drums at the NORM Decontamination Facility storage, were determined using gamma spectrometry. It was found that the highest concentrations were 2922, 254 and 1794 Bq g(-1) for 226Ra, 228Ra and 210Pb, respectively. A comparison to the reported worldwide values was made. Statistical approaches, namely Box plot, ANOVA and principal components analysis were applied on the total results. Maximal correlation was demonstrated by 226Ra activity concentration and count per second (cps) to density ratio. To obtain an accurate characterization of the radionuclides studied in the scale samples, method validation of gamma measurement procedure was carried out, in which minimum detectable activity, repeatability, intermediate precision and assessment of uncertainty were the parameters investigated. The work is a forefront for the proper and safe disposal of such radioactive wastes.

Distribution and baseline values of trace elements in the sediment of Var River catchment, Southeast France.

This study reports on the determination of trace element (TE)-Li, As, Co, Cs, Cu, Pb, U, and Zn-and major element (ME)-Si, Al, Fe, Mg, Ca, Mn, Na, and K-concentrations in 18 riverbed sediments and a sediment core from the Var River catchment using inductively coupled plasma mass spectrometry (ICP-MS). The results were compared with those of a reference sediment core, and the contribution of clay and organic carbon contents in the distribution of TE and ME in the sediment samples was investigated. The mean concentrations of the ME were comparable in both core and riverbed samples and were within the natural averages. In the case of TE, the concentrations were lower in riverbed sediment samples than those found in the sediment core. High mean concentration of As was observed (7.6 µg g(-1)) in both core and riverbed sediments, relatively higher than the worldwide reported values. The obtained data indicated that the natural high level of arsenic might be originated from the parent rocks, especially metamorphic rocks surrounding granites and from Permian sediments. Statistical approach, viz., Pearson correlation matrix, was applied to better understand the correlation among TE in both riverbed and sediment core samples. No significant metallic contamination was detected in the low Var valley despite of the localization of several industrial facilities. Therefore, results confirm that the concentrations of the TE obtained in the riverbed sediments could be considered as a baseline guide for future pollution monitoring program.