Sorption and separation performance of certain natural radionuclides of environmental interest using silica/olive pomace nanocomposites

Selective separation and purification of cerium (III) from concentrate liquor associated with monazite processing by cationic exchange resin as adsorbent

The present study is directed to find the optimal conditions required for efficient separation and purification of Ce3+ as an analog for lanthanides from Fe3+, Th4+, and Zr4+ (interfering ions) using Amberlite IR120H (AIR120H) resin as a strongly cationic exchange adsorbent. The main factors affecting the separation processes had been investigated and optimized. Ce3+ (Ln3+) as an admixture with Fe3+, Th4+, and Zr4+ was successfully separated by batch and column techniques. The sorption efficiency (S, %) from different acidic media was in this order: HCl > HNO3 > H2SO4. In a quaternary mixture with Fe3+ and Th4+, the maximum separation factor between Ce3+ and Zr4+ was ~ 13 after 90 min of equilibration, and the sorption capacity of AIR120H resin for Ce3+ was 8.2 mg/g. The rate of adsorption was found to follow a pseudo-second-order kinetic model. Separation of the absorbed ions was achieved by desorption processes. Firstly, 98 ± 2% of loaded Ce3+ is fully desorbed by 1 M sodium acetate solution without interfering ions. Moreover, ~ 95% of Zr4+ is desorbed by 1 M citric acid solution. Finally, 85% of loaded Fe3+ and Th4+ ions are desorbed with 8 M HCl solution. The batch technique was applied to separate and purify Ln3+-concentrate in chloride liquor (LnCl3), coming from the caustic digestion of Egyptian high-grade monazite. However, the enhanced radioactivity in LnCl3 due to radium -isotopes (228Ra2+, 226Ra2+, 224Ra2+, 223Ra2+) and radio-lead (210Pb2+) is initially reduced by a factor of 92% (i.e., safe limit) by pH-adjustment. As result, it can be recommended that the sorption process by AIR120H resin is efficient and promising for exploring pure lanthanides from its minerals.

Inclusion, occlusion and adsorption of rare earth elements from chloride media onto barite-gypsum composite

In this study, a synthetic BaSO4·CaSO4 composite was prepared by co-precipitation technique, characterised and examined for REE sorption. The sorption parameters were; pH = 4, equilibrium time = 20 min, temperature = 303 K, and REE liquor volume to composite mass ratio of 0.2:1 L g−1. The sorption reaction was controlled by pseudo 2nd order kinetic mechanism and Langmuir adsorption isotherm with an adsorption capacity of 168.63 mg g−1. 90.14% of REE (III) was desorbed using 1 mol L−1 HNO3. The process was endothermic and spontaneous. Accordingly, 1:1 barite-gypsum (natural ingredient for BaSO4·CaSO4), with 136 mg g−1 loading capacity, was used for REEs extraction.

A hybrid biocomposite of Thamnidium elegans/olive pomace/chitosan for efficient bioremoval of toxic copper

Immobilized biomaterials have recently attracted researchers' attention in the field of environmental biotechnology due to their effective biosorption performances. In this respect, a novel hybrid biocomposite based on Thamnidium elegans cells, olive pomace, and chitosan (TE-OP@C) was produced and tested for the first time to remove a target pollutant. It was successfully employed to eliminate toxic Cu (II) ions. Uptake efficiency of the biocomposite was significantly greater than that of T. elegans and T. elegans-olive pomace, despite the much lesser amount of biocomposite used. Freundlich model best fitted the equilibrium data, and the pseudo-second-order kinetic model followed uptake. The maximum removal efficiencies in batch and continuous systems were determined to be 96 % and 98 %, respectively. After eight cycles, the biosorption and recovery efficiencies of TE-OP@C were higher than 90 %. Biocomposite was able to remove approximately 90 % and 88 % of Cu(II) from real wastewater in batch and continuous systems, respectively. FTIR analysis, zeta potential measurements, EDX, and SEM findings confirmed the Cu(II) uptake. XRD and BET analysis were also performed for biocomposite characterization. Breakthrough and exhausted points were determined as 80 and 150 min, respectively. The findings potentially lead to a new perspective for the treatment of copper contamination.

Hydrogen Bonding with Polonium

Hydrogen bonding (H-bonding) with heavier chalcogens such as polonium and tellurium is almost unexplored owing to their lower electronegativities, providing us an opportunity to delve into the uncharted territory of...

Performance characteristics and validation of alpha particle spectrometers for radiometric analysis of natural and anthropogenic radionuclides of environmental impacts

Alpha spectrometry is one of the greatest nuclear techniques for identification and quantification of α-emitters in the environment due to nuclear fuel cycle operations, nuclear materials and geochemical studies or forensic medicine investigations. This study was conducted to re-evaluate and optimize the factors affecting the performance of a multi-chamber alpha spectrometer (EG&G Ortec) used in our laboratory using an aged α-source of ²³²U in equilibrium with its decay products. The results shown that the energy calibration within energy window 4-9 MeV has been done using alpha particle emissions of ²³²U (t_1/2.70.6 y) and its decay products with good linear fitting (R² > 0.999). At a source to detector spacing of 10 mm, the efficiency of the detectors varied between 15 and 20%; while the better resolution (FWHM) was ~36 keV. These values are lower than those warranted when supplied before 20 years. The minimum detectable activity (MDA) of the detectors varies between 0.8 and 3.1 mBq for the chamber in use. The alpha spectrometer was also verified by certified reference samples to measure activity concentration of alpha emitters (e.g., ²³⁸U, ²³²Th, ²²⁶Ra and ²⁴¹Am) with acceptable coefficient of variance (<10%), ζ-score (<3) and P-test (<25%). As a result, the optimized alpha spectrometer is valid and can be utilized for monitoring and assessment of natural and artificial α-emitters in different environmental compartments.

Development of a radiochemical method for extraction chromatographic separation of Pb and Bi radioisotopes of forensic and environmental interest

This work describes the purification and separation of some radionuclides of 210Pb and/or 210Bi that might be used in calibration of nuclear spectroscopic instruments for forensic purposes and environmental studies. The retention and desorption investigations have been done by Dowex HCR-S/S resin as the cationic exchanger by batch mode. Full retention of metal ions was achieved in 0.1 M HNO3 solution after an equilibration period of 2 h at room temperature. The uptake of Pb and Bi is reached to more than 95 and 85%, respectively. Desorption studies by several reagents indicated that 1 M citric acid and ammonium acetate are efficient to elute and separate Bi and Pb. Taking into consideration all the above obtained results, column applications packed by the Dowex HCR-S/S resin were carried out to separate 214,210Pb and 214Bi radionuclides either in TENORM-concentrate or old certified reference of 226Ra solution. The column application results revealed that the recovery of Pb and Bi radionuclides was ∼93%. In the radiochemical part, the eluted Bi was impure due to presence of 23% Pb. In contrast, 70% of pure Pb was obtained. Thus, the radionuclides 210Pb can be recovered from several waste resources by this method. It can be concluded that the Dowex HCR resin can be an alternative economic material that could be used to produce 210Pb from the TENORM wastes generated from some strategic industries.

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.