Initial Uranium Concentration Research Articles

Synthesis and adsorption characteristics of calix[6]arene derivative modified Aspergillus niger-Fe3O4 bio-nanocomposite for U(VI)

A new type of magnetic bioadsorbent (CDAB) was synthesized by reaction of amidoxime modified calix[6]arene derivative with the Aspergillus niger-Fe3O4 bio-nanocomposite, the bioadsorbent have been well characterized with FT-IR, SEM-EDS, XPS and VSM. The effects of various experimental parameters include pH, contact time, initial uranium(VI) concentration, adsorbent dosage and temperature on the bioadsorption of uranium(VI) were investigated in detail. Adsorption experimental results showed the adsorption process of CDAB was pseudo-second order kinetic model and Langmuir adsorption isotherm model. The maximum adsorption capacities of CDAB were calculated to be 77.04 mg g−1 for uranium(VI). The adsorption efficiency of CDAB towards U(VI) could reach at 83.6% with a considerable selectivity. In addition, the thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic.

Preparation of a Phosphate-Modified Flower-Like α-FeOOH Composite and Its Application for Aqueous U(VI) Removal

Goethite is a stable and widespread mineral in soil, which affects the transportation and immobilization of heavy metals in soil. Here, the three-dimensional flower-like goethite (TDFLG) was synthesized by refluxing precipitation method. The modified three-dimensional flower-like goethite (MTDFLG) was prepared by NaH2PO4 with dipping method. The obtained samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, N2 adsorption–desorption (BET), and X-ray diffraction (XRD). SEM images showed that the modification of phosphate had no major changes on the morphology of the original sample and the morphology of MTDFLG after adsorbed U(VI) had clearly change. For the goethite and modified goethite, the BET-specific surface area was 229.96 and 203.17 m2/g, respectively. Moreover, the effects of adsorption time, sorbent dose, solution pH, and initial uranium concentration on the uranium adsorption behaviors were investigated using the two materials as adsorbent for the treatment of uranium-containing wastewater. The results showed that MTDFLG had better adsorption capacity than TDFLG on uranium. The increase in uranium removal on MTDFLG was due to the formation of ternary surface complexes (≡FePO4UO2). TDFLG and MTDFLG followed the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model, which indicated that uranium adsorption on TDFLG or MTDFLG is mainly based on chemisorption, and the maximum adsorption capacity of two adsorbents is 48.24 and 112.36 mg/g, respectively.

Synthesis and characterization of a novel core–shell magnetic nanocomposite via surface-initiated RAFT polymerization for highly efficient and selective adsorption of uranium(VI)

In this work, the nanoparticles possessing a macro-initiator (MNPs@SCSOEt) were firstly obtained by surface-initiated RAFT polymerization. The structure of the nanocomposite was characterized by FT-IR, SEM, TEM, TGA, XPS and VSM. The effects of pH, contact time, initial uranium concentrations, coexisting ions and temperature on the U(VI) adsorption by MNPs@PAO were investigated in detail. The adsorption process was found to be in good agreement with pseudo-second order kinetic model and Langmuir adsorption isotherm model. The maximum adsorption capacity was estimated to be 216.45 mg/g by fitting Langmuir model with the equilibrium data. The adsorption process was endothermic and spontaneous. In addition, the adsorption capacity of MNPs@PAO for U(VI) decreased slightly after five successive adsorption/desorption cycles.

Kinetics and thermodynamics of uranium ion adsorption from waste solution using Amberjet 1200 H as cation exchanger

The present work deals with the adsorption of uranium from a nitric acid waste solution using the cation exchange resin Amberjet 1200 H (AHR) . Batch experiments were performed in order to assess the performance of AHR in uranium adsorption. The influences of pH, contact time, initial uranium concentration and temperature have been enhanced. The physical parameters including the adsorption kinetics, the isotherm models and the thermodynamic data have also been determined to determine the nature of the uranium adsorption by AHR. The studied resin has been agreed with both the pseudo second order reaction and Langmuir isotherm.

AMP and Ambersep 920 IRA anion exchange resins for recovery of uranium from productive solution

In the process of uranium production, one of the most important stages affecting the completeness of uranium extraction from productive solutions is the sorption stage. In order to study the effectiveness of ion exchange resins under dynamic conditions, sorption and desorption characteristics of anion exchangers, which used for recovery of uranium from sulfuric acid production solutions were studied. In laboratory conditions, sorption and desorption of uranium from productive solution on anion exchange resins of the brands Ambersep 920 IRA and AMP were carried out. During the research work, sorption and desorption characteristics were studied, as well as sorption capacity of the resins. Despite the fact that dynamic exchange capacities of the resins are equal, the sorption characteristics are different. The concentration of uranium in the desorption eluate for Ambersep 920 IRA and AMP was 856.00 and 268.00 mg/l, respectively, which is 5 and 1.5 times higher than the initial concentration of uranium in the productive solution. The most efficient anion exchanger, Ambersep 920 IRA, has been identified, which has good sorption and desorption characteristics compare to AMP.

Adsorption property of Br-PADAP-impregnated multiwall carbon nanotubes towards uranium and its performance in the selective separation and determination of uranium in different environmental samples

A newer efficient U(VI) ion adsorbent was synthesized by impregnating Br-PADAP [2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol] onto multiwall carbon nanotubes (MWCNTs). The effects of various operation conditions on uranium adsorption (i.e., pH contact time, temperature, and initial uranium concentration) were systematically evaluated using batch experiments. The results indicated that the uranium adsorption on modified MWNCTs (5.571 × 10−3g/mg × min) reached faster equilibrium than that on pristine MWNCTs (4.832 × 10−3g/mg × min), reflecting the involvement of appropriate functional groups of Br-PADAP on the chelating ion-exchange mechanism of U(VI) adsorption. Modified MWNCTs (83.4mg/g) exhibited significantly higher maximum Langmuir adsorption capacity than pristine MWNCTs (15.1mg/g). Approximately 99% of uranium adsorbed onto modified MWNCTs can be desorbed by 2.5mL of 1M HNO3 solution. Therefore, Br-PADAP-modified MWNCTs can server as a promising adsorbent for efficient uranium adsorption applications in water treatment. Subsequently, the proposed solid-phase extraction (using a mini-column packed with Br-PADAP/MWCNT) was successfully utilized for analysing trace uranium levels by the ICP-AES method in different environmental samples with a pre-concentration factor of 300-fold. The coexistence of other ions demonstrated an insignificant interference on the separative pre-concentration of uranium. the detection limit was recognized as 0.14μg/L, and the relative standard deviation was approximately 3.3% (n = 7).

Preparation of carbon coated Fe3O4 nanoparticles for magnetic separation of uranium

Uranium(VI) was removed from aqueous solutions using carbon coated Fe3O4 nanoparticles (Fe3O4@C). Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on uranium sorption efficiency. It was found that the maximum adsorption capacity of the Fe3O4@C toward uranium(VI) was ∼120.20 mg g−1 when the initial uranium(VI) concentration was 100 mg L−1, displaying a high efficiency for the removal of uranium(VI) ions. Kinetics of the uranium(VI) removal is found to follow pseudo-second-order rate equation. In addition, the uranium(VI)-loaded Fe3O4@C nanoparticles can be recovered easily from aqueous solution by magnetic separation and regenerated by acid treatment. Present study suggested that magnetic Fe3O4@C composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.

Sorption of uranium(VI) onto hydrous ferric oxide-modified zeolite: Assessment of the effect of pH, contact time, temperature, selected cations and anions on sorbent interactions

Zeolites are commonly used as adsorbents for metal removal in most applications e.g. in wastewater. However, the ubiquity of iron in such systems may, in the long-term, distort the true interactions and mechanisms of contaminant removal as a result of modification of the zeolite surface. In this study, this potential phenomenon was assessed for the removal of uranium(VI) from aqueous solution by hydrous ferric oxide-modified zeolite (HFOMZ). This was prepared by precipitating iron hydroxide (the common precipitate of iron in aqueous systems) onto zeolite. The prepared HFOMZ was characterised by the scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Batch adsorption experiments were performed to assess the effect of: pH, initial uranium(VI) concentration, adsorbent dosage, contact time, temperature, presence of cations (Pb2+, Cr3+, Cu2+, Mn2+ and Co2+) and anions (SO42−, CO32− and HPO42−) on the adsorption of uranium(VI). Kinetic studies under these conditions indicated that the pseudo second-order kinetic model (R2 > 0.99) best described the adsorption behaviour, implying that this could be proceeding through a chemisorption process. The experimental data was best described by the Freundlich isotherm model (R2 > 0.93), an implication that the adsorption surface was heterogeneous. The thermodynamic parameters calculated from the experimental data suggested that the adsorption of U(VI) onto HFOMZ was spontaneous and exothermic in nature. The adsorption of U(VI) onto HFOMZ was dominated by complexation with strong ionizable hydroxyl sites on the hydrous ferric oxide surfaces and the edge sites of the zeolite. At pH values from 2 to 6, increased adsorption was observed and this decreased at higher pH values (above 6). This corresponded with the changes in speciation as determined by the PHREEQC modelling code. The presence of the cations (Pb2+, Cr3+, Cu2+, Mn2+ and Co2+) and anions (CO32− and HPO42−) resulted in a significant decrease in the adsorption capacity of U(VI) by HFOMZ, implying that in a system where these anions and cations are present in high concentrations over time, U(VI) will adsorb less onto the material.

Factors influencing the sorption and migration behavior of uranium in shale

The sorption of U(VI) on shale has been experimentally investigated as a function of pH, initial uranium concentration, rock particle size and water–rock ratio. The results showed the sorption equilibrium time was about 10 days, and the adsorption capacity presented a negative relationship with rock particle size and positive correlation with the liquid–solid ratio, also influenced by pH. The sorption process was fitted well with Freundlich isotherm. Experimental column was fully penetrated by tritium at about 230 min with a velocity of 0.13 cm/min while uranium was not penetrated the rock column in 180 days.

Preparation and application of alginate-Ca/attapulgite clay core/shell particle for the removal of uranium from aqueous solution

Alginate-Ca/attapulgite clay core/shell particles were synthesized via electro-coextrusion. Affecting parameters on the removal of uranium, such as pH, initial uranium concentration, temperature and co-existing cations were investigated. The uranium adsorption process was endothermic, feasible and spontaneous. The maximum adsorption capacity of the adsorbent for uranium was 199.345 mg/g at pH 3 and at 328.15 K. The results showed that the pseudo-second-order model and the Langmuir isotherm model fitted well with the data obtained. Based on the adsorption–desorption study, the adsorbent shows excellent reusability. The mechanism of uranium adsorption on the adsorbent was a combination of ion-exchange and an electrostatic interaction.

Interaction mechanism of uranium(VI) with three-dimensional graphene oxide-chitosan composite: Insights from batch experiments, IR, XPS, and EXAFS spectroscopy

Aiming at the efficient and convenient treatment of radioactive wastewater, a graphene oxide-chitosan aerogel (GO-CS) was fabricated and utilized for uranium(VI) elimination. The adsorption of U(VI) on the aerogel was evaluated as a function of contact time, solution pH, ionic strength, initial uranium concentration, and competing metal ions. High adsorption capacity for the uranium could be achieved over a wide pH range, e.g., 200, 319.9, and 384.6mg/g at pH 3.5, 5.0, and 8.3, respectively. The interaction mechanism of U(VI) with GO-CS was systematically clarified by using Fourier transformation infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy (EXAFS). It was found that the U(VI) adsorption was mainly ascribed to the inner-sphere surface complexation by –COO−, –OH, and –NH2 groups anchored on the GO-CS and the involvement of these functional groups toward the coordination sphere was largely relevant to solution pH. At mild alkaline pH, –NH2 groups play a more important role, therefore leading to an extraordinarily high extraction of uranium from simulated seawater.

Preparation of graphene oxide–chitosan composite and adsorption performance for uranium

The composite adsorbent graphene oxide–chitosan was prepared using graphite and chitosan as the initial materials. The structures and morphology of the products were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. The products were used to remove uranium from aqueous solution by batch adsorption experiments. The effects of pH, adsorbent dosage, contact time, initial uranium concentration and temperature on the uranium removal were investigated, and the results were fitted by the adsorption isotherm models. The adsorption kinetic and thermodynamic were also studied in detail.

Phytoremediation of Jordanian Uranium-Rich Soil Using Sunflower

Uranium-contaminated environments pose a risk to human health by means of its transfer to the food chain. Overcoming this issue requires using effective methods to minimize the availability of uranium and other metals in soils. Jordan has a promising project for electricity generation from nuclear power. To move forward with this nuclear project, the Jordan Central Area has been mined for uranium. The expansion of the mining activities in this area led to elevated contents of heavy metal in the surface soil. Phytoremediation efficiency in reducing uranium content from uranium-rich carbonate soil was tested using sunflower plants. Forty-eight sunflower plants were planted in three soil samples containing three different uranium concentrations. The plants were harvested after different planting periods in order to investigate the phytoremediation efficiency over time. The ability of sunflowers to translocate uranium was investigated and the results showed that the translocated amount of uranium to plant increased as the initial concentration of uranium in the soil increased. However, most of the uranium taken up by the sunflower was accumulated in the roots, and only 3% of the uranium concentration in the roots passed to the harvestable shoots. Moreover, the biomass of the plants was not affected by increasing uranium concentration in the plants indicating that sunflower is resistant to radiation and toxicity of uranium at these levels found in the soil.

ADSORPTION OF URANIUM FROM AQUEOUS SOLUTION BY DRY AND CHEMICAL MODIFIED WATER HYACINTH ROOTS

Adsorption of uranium using dried roots of water hyacinth plant (E. crassipesas) has been investigated. The plants were collected from Ismailia canal, Sharkia Governorate, Egypt. And pretreated with different activating agents as organic or metallic acids, using fixed concentration from each activator (5%). The adsorption were examined as a function of initial uranium concentration, contact time, pH, temperature, volume, dose of roots and size. Citric acid has advantage and the optimum condition was 94% about pH of 5.

Enhanced Photocatalytic Removal of Uranium(VI) from Aqueous Solution by Magnetic TiO2/Fe3O4 and Its Graphene Composite.

The separation and recovery of uranium from radioactive wastewater is important from the standpoints of environmental protection and uranium reuse. In the present work, magnetically collectable TiO2/Fe3O4 and its graphene composites were fabricated and utilized for the photocatalytical removal of U(VI) from aqueous solutions. It was found that, under ultraviolet (UV) irradiation, the photoreactivity of TiO2/Fe3O4 for the reduction of U(VI) was 19.3 times higher than that of pure TiO2, which is strongly correlated with the Fe0 and additional Fe(II) generated from the reduction of Fe3O4 by TiO2 photoelectrons. The effects of initial uranium concentration, solution pH, ionic strength, the composition of wastewater, and organic pollutants on the U(VI) removal by TiO2/Fe3O4 were systematically investigated. The results demonstrated its excellent performance in the cleanup of uranium contamination. As graphene can efficiently attract the TiO2 photoelectrons and thus decrease their transfer to Fe3O4, the photodissolution of Fe3O4 in the TiO2/graphene/Fe3O4 composite can be largely alleviated compared to that of the TiO2/Fe3O4, rendering this ternary composite a much higher stability. In addition, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS) were used to explore the reaction mechanisms.

REMOVAL OF URANIUM FROM LIQUID WASTE BY NATURAL NILE MUD

This effort deals with uranium removal from liquid waste using Natural Nile Mud (NNM). Accordingly, cost effective and simple approach to remove uranium from liquid waste by NNM was reported. The effects of shaking time, pH, the initial uranium concentration, adsorbent temperature, adsorbent amount (dose) and effect of foreign ion (iron) on the adsorption of uranium ions from liquid waste were examined. According to the results, the optimum conditions for maximum adsorption efficiency of the NNM for uranium from the solution were obtained fitted with the Langmuir and the maximum adsorption capacity was about 61 mg/g NNM.

Adsorption of Uranium(VI) from a Simulated Saline Solution by Alkali-Activated Leather Waste

A porous adsorbent was prepared from leather waste by activation with alkali. The adsorbent, alkali-activated leather waste (AALW), was applied to adsorb uranium(VI) and characterized by scanning electron microscopy, energy-dispersive X-ray detection, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The influence of the pH, initial uranium(VI) concentration, temperature, and contact time on the adsorption of uranium(VI) was systematically investigated. The adsorption of uranium(VI) on AALW obeyed the Langmuir isotherm model and was attributed to ion exchange and complexation coordination. Thermodynamic and kinetic studies showed that the adsorption process was spontaneous and endothermic, and it reached adsorption equilibrium in 360 min. Moreover, the selective adsorption of uranium(VI) from an aqueous solution containing coexisting ions and adsorption of trace uranium(VI) from a simulated high-salinity environment showed that AALW had not only a strong affinity but a high se...

Sorption of uranium from waste effluent solutions by mesoporous carbon impregnated with trioctylamine

A new mesoporous adsorbent for uranium removal from waste effluents was prepared, characterized, and impregnated with trioctylamine. The adsorption efficiency was investigated as a function of pH, contact time, initial uranium concentration, competing ions, solid/liquid ratio, and temperature using batch sorption techniques. The maximum adsorption capacity was 21.9 mg g–1 at pH 5. The equilibrium data fit well with the Langmuir adsorption isotherm. Kinetic study showed that the process was fast and reached equilibrium within 60 min. The kinetic data fit well with the pseudo-second-order law. Thermodynamic data show that the process is spontaneous and exothermic.

Recovery of uranium(VI) from aqueous solution by 2-picolylamine functionalized poly(styrene-co-maleic anhydride) resin

A 2-picolylamine functionalized poly(styrene-co-maleic anhydride) resin was synthesized and characterized by FT-IR, elemental analysis, SEM and XPS. To recover uranium from aqueous solution, the influence factors such as pH values, contact time, temperature and initial uranium concentration were optimized. Adsorption kinetics fitted well with the pseudo-second-order model, whereas adsorption isotherm matched well with the Langmuir isothermal adsorption model, with the maximum sorption capacity of 518.39mgg−1 at pH 5.30 and 298K. The uptake of uranium could be implied in 0.01M coexisted ions environment. Besides, the resin could be regenerated by 0.1M HNO3 and repeatedly utilized in circles. The study proved that the resin has potential application prospects for disposal of uranium(VI).

Isotherms, thermodynamic and mechanism studies of removal of low concentration uranium (VI) by Aspergillus niger.

In order to develop an effective and economical method for removing low concentration radioactive wastewater of uranium, the biomass of 'CMCC(F)-98003' Aspergillus niger was investigated in a batch system. The maximum uranium adsorption capacity of 12.5 mg g-1 was obtained at the initial uranium concentration of 0.75 mg L-1. The biosorption data on a biomass concentration of 0.029 g L-1 fitted well to the Freundlich isotherm with a correlation coefficient (R2) of 0.987. The calculated thermodynamic parameters showed that the biosorption of uranium ions was endothermic (ΔH° < 0). The results of scanning electron microscope and Fourier transform infrared spectrometry analysis revealed that nano-particles of uranium precipitation were formed on the cell surfaces after biosorption, and the functional groups of -CH, N-H, -COOH, P = O and the carbohydrates and alcohols were involved in the biosorption process between A. niger and uranium ions.