Band 112, Heft 6

The complexation and separation behaviour of trivalent actinides and lanthanides with various multiple diglycolamide (DGA) group-containing ligands are compiled in the present review. The DGA arms are anchored on various scaffolds, viz., C- and N-pivot tripodal backbones, benzene-centred tripodal backbones, calix[4]arene, pillar[5]arene and azamacrocycle scaffolds. Dendrimers of different generations having DGA arms were also evaluated for the extraction and complexation studies of trivalent actinide and lanthanide ions. The extraction efficiency of the DGA units increases significantly when they are grouped together on a single backbone/scaffold. Furthermore, the selectivity was found to improve in many cases, particularly with respect to the UO 2 2+ ion. This is very important for the development of suitable ligands for the extraction/separation of the actinide and lanthanide ions. Combined experimental, luminescence and DFT studies on the complexation of trivalent actinides and lanthanides with these DGA-based ligands are quite useful to understand their extraction and separation behaviour and this review article gives a critical analysis of the results available in the literature.

A mechanistic modelling of the adsorption processes onto individual minerals presenting in the near- and far-fields can greatly enhance the credibility of long-term safety assessments of granite-based geological repositories. In this study, the titration and U(VI) adsorption characteristics of chlorite, one of the major minerals of rock fractures, have been studied. Potentiometric titration curves at two ionic strengths (0.1 and 0.4 mol/L NaCl) are successfully interpreted by considering protonation/deprotonation reactions on generic edge sites (≡SOH) in the framework of a non-electrostatic surface complexation model (SCM). The adsorption of U(VI) on chlorite was reached after 24 h, the adsorption kinetics can be described by a pseudo-second-order model. A non-electrostatic SCM with three surface complexes (≡SOUO 2 + , ≡SO(UO 2 ) 3 (OH) 5 and ≡SO(UO 2 ) 3 (OH) 7 2− ) was set up based on pH edges of U(VI) at adsorption equilibrium in the absence of CO 2 . Additional, experimental data measured as a function of U(VI) concentration, solid-to-liquid ratio and carbonate concentration were well reproduced by the proposed model. Finally, parallel experiments were conducted using X-ray photoelectron spectroscopy (XPS) to analyze the variation of U(VI) surface species speciation at different pH values. The good agreement between SCM prediction and XPS analysis demonstrates the reliability of the model in predicting and quantifying the radionuclides retention by chlorite.

This study determines uranium concentrations and isotopes ( 238 U, 235 U, and 234 U) in baby food samples collected from Iraqi markets using solid-state nuclear track detector technical (CR-39). Also, some radiological hazard parameters such as annual committed effective dose ( E U ) and risk of an excess cancer fatality per million persons (RECFPMP) for the same study samples were calculated using theoretical equations. The samples in the present study were classified into three varieties: cereals and cereal products, vegetables and fruits, and biscuits. The results show that the average uranium concentration (mg/kg or ppm) values in cereals and cereal products, vegetables and fruits, and biscuits were 0.71 ± 0.01, 0.81 ± 0.04, and 0.72 ± 0.031, respectively. At the same time, the average values of 238 U, 235 U, and 234 U in all samples of the present study were 9.08 ±0.17 Bq/kg, 0.42 ± 0.0081 Bq/kg, and 9.33 ± 0.18 Bq/kg, respectively. The total average of E U (mSv/y) due to all uranium isotopes ( 238 U, 235 U, and 234 U) in cereals and cereal products, vegetables and fruits, and biscuits were 0.042 ± 0.0006, 0.039 ± 0.001, and 0.034 ± 0.001, respectively. Moreover, it was found that the average values of RECFPMP were 0.159 ± 0.002 in cereals and cereal products samples, 0.154 ± 0.007 in vegetables and fruits samples, and 0.130 ± 0.005 in biscuits samples. Uranium concentrations and the total annual committed effective dose in all baby food samples comply with the worldwide limits approved by UNSCEAR, which state safe limitations (1.7 mg/kg) and (0.32 mSv/y), respectively. So, one may conclude that there is no danger of uranium concentrations in the case of baby consumption.

The presence of chromate in the aquatic environment poses toxicity and pollution to the environment. Therefore, the needs to establish methods to get rid of this species is a must. The effect of different natural rock minerals; pyrite, magnetite, pyrrhotite, and wurtzite as constituent parts of the Earth’s crust can play a major role in waste treatment. The properties of those minerals towards the behavior of chromium (sorption) were studied under the effect of changes of pH and contact time to treat the waste solution of toxic chromate. The total chromium species in the reaction system was determined using Cr 51 as a simpler, faster and more accurate analytical tools. Concerning the effect of types of minerals, the synthetic ones, the results indicated that pyrrhotite and wurtzite were highly effective for the removal of chromate with almost 100 % sorption capacity as it was pH-independent, despite the presence of a degree of reductive ability of both minerals. While, it was 99 % at pH 8.5 and 28 % at pH 3 for pyrite and magnetite, respectively, which was pH dependent. The equilibrium adsorption capacities for chromium adsorption were 0.34 ± 0.15, 0.028 ± 0.01 and 4.27 ± 1.3 mg/g mineral for natural minerals pyrite, magnetite and synthetic one pyrhotite, respectively. However, it was found 117.7 ± 10.9 mg/g for synthetic mineral wurtzite. These results can be attributed to the redox power of oxide and sulfide minerals; magnetite and, pyrite used. For kinetic studies of chromium (VI) adsorption, non linear model approved that the reaction could be described based on pseudo-second-order kinetics in such simulated environmental heterogeneous systems.

A comparative study was carried out between ionizing radiation and dicumyl peroxide (Dicup) as two different curing systems for nitrile rubber (NBR) reinforced with different concentrations of multi-walled carbon nanotubes (MWCNTs). Upon ionizing irradiation, the tensile strength (TS) of the composites increases with increasing absorbed dose up to 50 kGy and then decreases with increasing absorbed dose. TS also increases with increasing of MWCNTs content up to 0.75 phr (part per hundred part of rubber). TS values are decreased in the case of Dicup curing as compared with radiation curing. Other characterizations were made, such as the Differential Scanning Calorimeter (DSC), Fourier transform infrared spectroscopies (FTIR), and morphological characterization, which give further implications for the good compatibility between MWCNTs and NBR phases. A study of the effect of fuel on NBR/MWCNTs composites showed that the composites cured by Dicup had lower values for swelling in fuels when compared with others that were cured by radiation.

The most common ways to produce nanoparticles are through chemical and physical processes, which can be expensive and environmentally hazardous. Using plant extracts (green synthesis) as reducing and capping agents is a simple, cost-effective, and environmentally friendly method of lowering the usage of dangerous chemicals in the synthesis of metal nanoparticles. This study covers the environmentally friendly synthesis of cadmium sulphide nanoparticles (CdS NPs) using a blend of flaxseed extracts (FM), polyvinyl alcohol (PVA), and chitosan (Cs). The composites are then exposed to gamma irradiation at doses of 20 kGy and 40 kGy. UV–VIS absorption spectroscopy, SEM, HRTEM, EDX, and FTIR were used to analyse the produced nanocomposite films. UV–Vis absorption spectra showed considerable surface Plasmon resonance (SPR) bands at 396–440 nm, indicating that CdS NPs had been successfully synthesized. A progressive red shift in wavelength was noted, along with the broadening of the absorption band as the irradiation dose increased. Transmission electron microscopy pictures revealed that the generated CdS nanostructures were dispersed as spherical nanoparticles with remarkable structural homogeneity. Tensile strength and elongation measurements of the films revealed that the inclusion of CdS NPs improved their mechanical properties. The addition of CdS NPs to the current blends limits biodegradation in soil. Thermal gravimetric analysis findings showed that CdS NPs included in FM/PVA films had improved thermal stability. The antimicrobial activities of the tested films were performed against Staphylococcus aureus , Escherichia coli , and Candida albicans . The results revealed that all of the films exhibited more antibacterial activity against S. aureus than the two others, with the highest activity observed in nanocomposites with a high concentration of CdS.