Search

The present study is conducted for developing separation of some elements of nuclear interest from zirconium-concentrate explored from Egyptian zircon mineral, using certain cationic exchangers. Th...

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.

This study is concerned with the sorption behavior of natural radionuclides (226Ra, 210Po, 228Th—originated from TENORM waste associated with petroleum industry) onto silica/olive pomace nanocomposite. Initially, nanocomposites of extracted silica and olive pomace are prepared and characterized by physicochemical techniques. In the batch technique, 60% SiO2 40% olive pomace (AM3) nanocomposite showed a considerable group sorption for 226Ra and 210Po larger than 228Th in 1M HNO3 and HClO4 solutions. In case of sorption by the compacted disc, sorption of 226Ra was similar to batch method, sorption of 228Th increased slightly to ~ 17%, while sorption of 210Po was decreased to 77%. Thus, AM3 nanocomposite can be considered as an efficient nano-adsorbent for sorption and separation of Ra-isotopes and 210Po-radionuclides from 226Ra–210Po–228Th admixture associated with nuclear and non-nuclear industries.

In this article, new two approaches (A and B) are created for the efficient removal of the technically enhanced radium isotopes (228Ra, 226Ra and 223Ra), long-lived radioisotope of lead (210Pb), thorium (Th4+) and iron (Fe3+) from the rare earth chloride (RECl3) liquor produced during the monazite processing. In the first approach ‘A,’ elimination of the undesired species is achieved using a synergistic admixture of sulfate–sulfide solution (SO42−/S2− admixture), while the second approach ‘B’ is performed using an iodate solution (IO3−) as a selective precipitating agent. The results indicated that 14% of radionuclides and Th(IV), 12% of Ln(III) and 40% of Fe(III) were removed from the RECl3 liquor at pH 3. In the first approach ‘A,’ the average percentage removal (%R) of all the undesired species reached ~ 96% using sulfate–sulfide admixture (0.058/0.04 mol/L). In the second approach ‘B,’ the average % R of all undesired species is improved and increased to ~ 99% using potassium iodate solution of 0.155 mol/L. Therefore, iodate solution is considered as an efficient and selective agent for the removal of Ra isotopes, 210Pb, Th(IV) and Fe(III) from RECl3 liquor without loss in Ln(III) at the optimized conditions. In this respect, promising results are obtained for the purification and production of Ln(III) using iodate solution or sulfate–sulfide admixture. Finally, the proposed two approaches are considered to be efficient not only to minimize the radiological human risks but also to eliminate the interfering of Th and Fe ions, to produce highly purified lanthanides from monazite ore.

Removal of the non-desired impurities (radionuclides, Th(IV) and Fe(III)) with Ln(III) in high-grade monazite was developed. The chromate solution and pH are the factors controlling removal of the non-desired impurities. At pH 3, removal of radionuclides and Fe(III) was 30 and 60%, respectively, whereas Th(IV) interfered with Ln(III) liquor. When liquor was treated by 0.23 M chromate solution at pH 3, ~ 98% of Th(IV) and Fe(III) was removed and ~ 70% of radionuclides was removed from Ln(III) liquor with loss ≤ 20% is low compared with a previous study. Thus, exploitation of valuable Ln(III) can be done safely using the optimized chromate solution.

Three synthetic hematite (SH) materials as iron oxides nanofibers were prepared and applied for the removal of 51Cr and radioiodine (131I) as anions associated with nuclear industry technology. The results exhibited that 70% of Cr(VI) and 90% of 131I were removed from aqueous solution using the SH1 adsorbent. In acid solutions, R % of Cr(VI) increased to > 90% with the decrease in concentration till 0.05M, while the R % of 131I was 94 and 79% at HNO3 and HCl, respectively. It was concluded that SH1 nanofibers is promising and selective adsorbent for Cr(VI) and 131I removal from aqueous or acid solutions.

Egyptian monazite is a promising resource and investment attractive for production of valuable metals of industrial or nuclear interest such as rare earth elements (REEs), thorium (Th) and uranium (U). The study was focused to establish a baseline framework in viewpoint of radiation protection for the workers in production of REEs from high-grade monazite treated by sodium hydroxide (NaOH) solutions. Radiological hazard indices (cancer, gonadal and other risks) were evaluated, due to emissions (α-, β- and γ-radiations) of radium-isotopes (228Ra, 226Ra, 223Ra) and lead (210Pb). The values of the estimated radiological hazard indices were higher than the permissible safe limits, worldwide average and varied with those reported in other countries. It was found that more than 70% of radioactivity and radiological hazardous indices resulted from emissions of 228Ra, while the rest was attributed to 226Ra, 223Ra and 210Pb. Therefore, processing of the Egyptian monazite can cause a significant radiological impact on workers through external exposure from γ-radiations and/or internal exposure through inhalation or ingestion airborne contaminated by the radionuclides. Thus, the results recommended that protection rules could be considered to prevent the radiation hazards associated with the production of the REEs from the high grade monazite attacked by caustic method.

This work is directed for removal of the nondesired species (228Ra, 226Ra, 223Ra, 210Pb, Th(IV) and Fe(III)) in the rare earth chloride (RECl3) liquor before separation of Ln(III). The different factors affecting elimination of radium-isotopes, lead (210Pb), Th(IV) and Fe(III) from the RECl3 liquor, have been investigated and optimized. The results indicated that the activity concentration of radionuclides in RECl3 liquor was above the safe limits required during the separation process of Ln(III). Adjustment of pH 3±0.1 leads to eliminate 14±1% of radionuclides and Th(IV), and 40±3% of Fe(III), while 12±1% of Ln(III) was lost. The developed method shows that more than 95% of the nondesired species was selectively removed when the liquor was eliminated by potassium sulfate or sulfuric acid solutions in presence of Ba/Pb-carrier (1: 1). About 20-83% of Ln(III) was lost when the non-desired species removed by sodium or ammonium sulfate or potassium chromate solutions. Fe(III) interfered with Ln(III) when radionuclides and Th(IV) were eliminated by 2.6M H2SO4 in presence of Ba/Pb-carrier. Finally, use of 0.23M K2SO4 or 2.6M H2SO4 was efficient to reduce level of 228Ra, 226Ra, 223Ra and 210Pb to the safe limits in viewpoint of radiation protection. In addition, the interfered Th(IV) and Fe(III) were also eliminated efficiently from RECl3 liquor before the chemical processing of Ln(III).

This study investigated the leaching of radium-226 from phosphogypsum (PG) waste produced from the fertilizer industry by synthetic solutions that replicate water that may contact the waste in natural conditions. The results indicated that the activity concentration of Ra-226 in the PG was 461 ± 12 Bq kg−1 and compared with other studies carried out worldwide. The leached percentage of Ra-226 represents the exchangeable fraction loosely bounded in the matrix of the PG waste. The leached fraction of Ra-226 was 6.5 ± 0.6 and 9.0 ± 0.5% when the waste was exposed to rainwater and saline solution, respectively. It is also found that the leaching fraction increased 10–12 ± 0.4% when the waste was exposed to the admixture of saline solution containing Sr2+ or Ba2+ cations, whereas it was lowered to 4–5 ± 0.5% in the presence of carbonate or sulfate anions. When the PG is used as an economic fertilizer, the irrigation water can leach 7.8 ± 0.6% of Ra-226 that could contribute to plant uptake, thereby to animal and/or human consumption. The primary tests of the drinking water (well and tap resources) consumed by the populations surround the PG facility showed that the activity concentration of Ra-226 was below the minimum detectable activity.

This study is conducted to find the conditions required to synthesize composite material for cesium (134Cs+) removal from the generated liquid waste associated with nuclear, medical, industrial, and/or research activities. The study shows that the optimum conditions required for synthesizing “Poly [acrylamide (AM)-itaconic acid (IA)]/N,N′-methylenediacrylamide (DAM)/Zirconium tungstate (ZrW)” or “Poly(AM-IA)/DAM/ZrW” are 0.01 g DAM dose as a cross-linker, a co-monomer concentration of 20%, a co-monomer composition (AM-IA) (12:88), and 0.03 g (melted at 450 °C–500 °C) ZrW with gamma irradiation dose of 30 kGy. The composite material was characterized by Fourier infrared (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption performance of the composite was investigated. The maximum removal efficiency of 134Cs+ ions was found to be 93% in m...

The aim of this study is oriented to investigate the influence of some physicochemical factors such as radium distribution, grain size, moisture content and chemical constituents on releases of radon-222 from the accumulated phosphogypsum (PG) waste. The emanation fraction, activity concentration in the pore and the surface exhalation rate of radon-222 in the bulk PG waste are 34.5 ± 0.3%, 238.6 ± 7.8 kBq m(-3) and 213 ± 6.9 mBq m(-2) s(-1), respectively. These values were varied and enhanced slightly in the fine grain sizes (F1 0.125 mm) by a factor of 1.05 folds compared to the bulk residue. It was also found that release of radon from residue PG waste was controlled positively by radium (Ra-226), calcium (CaSO4) and strontium (SrO). About 67% of radon release attributed to the grain size below 0.5 mm, while 33% due to the large grain size above 0.5 mm. The emanation fraction of Rn-222 is increased with moisture content and the maximum emanation is ∼43% of moisture of 3-8%. It reduced slowly with the continuous increase in moisture till 20%. Due to PG waste in situ can be enhancing the background to the surround workers and/or public. Therefore, the environmental negative impacts due to release of Rn-222 can be minimized by legislation to restrict its civil uses, or increasing its moisture to ∼10%, or by the particle size separation of the fine fraction containing the high levels of Ra-226 followed by a suitable chemical treatment or disposal; whereas the low release amount can be diluted and used in cement industry, roads or dam construction.

The feasibility of using surfactants as extracting agent for the removal of radium species from TENORM sludge produced from petroleum industry is evaluated. In this investigation cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both (226)Ra and (228)Ra by the two surfactants as well as their admixture were studied by the batch technique. These parameters include effect of shaking time, surfactants concentration and temperature as well as the effect of surfactants admixture. It was found that, higher solution temperature improves the removal efficiency of radium species. Combined extraction of nonionic and cationic surfactants produces synergistic effect in removal both (226)Ra and (228)Ra, where the removals reached 84% and 80% for (226)Ra and (228)Ra, respectively, were obtained using surfactants admixture.

Treatment of TENORM scale wastes generated from oil and gas production that contaminated by different radionuclides is an important societal, environmental, economical and technological challenge, due to the rise number of sites contaminated by these radionuclides. Bench-scale laboratory experiments were conducted to determine the removal characteristics of radium isotopes from TENORM-scale. This scale waste contained high level radioactivity (44,610 Bq/kg) due to the presence of radium isotopes (35,100 Bq/kg for 226Ra and 9510 Bq/kg for 228Ra). In this study, three different types of surfactants polyoxyethylene sorbitanmonooleate (Tween-80), cetyltrimethylammonium bromide (CTAB) and sodium-dodecylsulfate (SDS) as micelle-forming agents were used for treating scale wastes by separating the most contaminated fraction of the TENORM-scale for disposal. It is found that the highest efficiency of radium isotopes was about 52% and 55% for 226Ra and 228Ra, respectively using single micelles systems. Combined effect of mixed micelles produces synergistic effect in the remediation process, where the removals reached to about 80% for 226Ra and 228Ra were obtained using mixed micelles solutions. The scale-washing process water used in TENORM scale extractive washing is treated with conventional wastewater treatment technology or reused in successive washing for new scale waste. The results also point out that the treated water from the washing step was more effective compared to distilled water, probably due to surfactants contained in treated water. The data obtained in these studies may be considered as promising and efficient to treatment of TENORM scales economically.

Lanthanum, cerium, neodymium, and samarium were sorption from aqueous solutions using zirconium titanate (ZrTi) and polyacrylonitrile zirconium titanate (PANZrTi) ion exchangers. The characterizations of prepared materials were performed using XRD, SEM, FTIR, TGA, and DTA techniques. The sorption behavior of various ions toward synthesized resin has been studied depending on reaction temperatures, pH values, and initial concentrations. The selectivity order found is Sm3+ > Nd3+ > Ce3+ > La3+ on ZrTi-100, Ce3+ > Sm3+ ≈ Nd3+ > La3+ on ZrTi-150, and Sm3+ ≈ Ce3+ > Nd3+ > La3+ on PANZrTi depending on the condition of prepared ZrTi samples. The Kd for lanthanide ions was slightly decreased with temperature increased, which indicated the exothermic nature. The sorption data obtained for equilibrium conditions have been analyzed using the different isotherm models, and the applicability of these isotherm equations was compared by the correlation coefficients, R2. It was established that the equilibrium isotherm models’ applicability follows the order: Langmuir > Dubinin– Radushkevich > Freundlich. It is found the Ce3+ has high adsorption capacity on each of ZrTi-100 and ZrTi-150, while Nd3+ has high adsorption capacity on PANZrTi.

Regarding to their presence as an important constituent in some ores such as monazite, this work aims for selective solvent extraction of thorium (IV), zirconium (IV), iron (III) and cerium (III) from aqueous sulfate medium using different basic and acidic extractants. To elucidate the extractability of these elements, different effective parameters were studied such as contact time, pH value, extractant concentration and the diluents type. In a single element system, Th (IV) was extracted by the primary amines (octylamine and tert.octylamine) and the acidic extractnts [di-(2-ethylhexyl) phosphoric acid (D2EHPA) and (bis(2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272))]. Moreover, secondary amine (N-methylaniline) is effective for Fe (III) extraction while, the primary amines are suitable for Zr (IV) extraction. Ce (III) can be extracted with the primary amines and D2EHPA. In a mixed elements system, Th (IV) was extracted firstly with Cyanex 272 (65 %) atpH1 followed by the extraction of Fe(III) with N-methylaniline (95 %), then Zr (IV) was precipitated atpH2.5 (84 %) whileCe(III) remains in the final aqueous phase.

Potential utilization of hematite as a natural material for immobilization of long-lived radionuclides from radioactive liquid waste was investigated. Hematite ore has been characterized by different analytical tools such as Fourier transformer infrared (FTIR), X-ray fluorescence (XRF), powder X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal (DT) analysis, scanning electron microscopy (SEM) and BET-surface area. In this study, europium was used as REEs(III) and as a homolog of Am(III)-isotopes (such as (241)Am of 432.6 y, (242m)Am of 141 y and (243)Am of 7370 y). Micro particles of the hematite ore were used for treatment of radioactive waste containing (152+154)Eu(III). The results indicated that 96% (4.1 × 10(4) Bq) of (152+154)Eu(III) was efficiently retained onto hematite ore. Kinetic experiments indicated that the processes could be simulated by a pseudo-second-order model and suggested that the process may be chemisorption in nature. The applicability of Langmuir, Freundlich and Temkin models was investigated. It was found that Langmuir isotherm exhibited the best fit with the experimental results. It can be concluded that hematite is an economic and efficient reactive barrier for immobilization of long-lived radio isotopes of actinides and REEs(III).