Removal Of Uranyl Ions Research Articles

Removal of uranyl ions in aquatic mediums by using a new material: Gallocyanine grafted hydrogel

A new material containing gallocyanine (GC) grafted polyacyril amide (PAA) was synthesized and its adsorption ability was examined for the removal of uranyl ions from aqueous media. The new developed adsorbent was characterized by FTIR, SEM, and PZC analysis. Adsorption of UO22+ ions from aqueous solution as a function of ion concentration, pH, ionic strength, temperature, and reusability of adsorbent was investigated in detail. The adsorption data were analyzed by using the Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption of UO22+ increased with pH and reached a plateau value in the pH range 5–6. The adsorption of UO22+ ions were not affected by increasing ionic strength. The adsorption mechanism followed an endothermic and spontaneous process with increased disorderliness at adsorbate/adsorbent interface. The adsorption process followed a pseudo-second-order kinetics. The new developed material is a potential adsorbent for effective removal of uranyl ions from aquatic solutions.

Removal of uranyl ions from UO2(NO3)2 solution by means of Chlorella vulgaris and Dunaliella salina algae

Abstract This paper deals with a study of the biosorption of UO22+ ions on two green algae: Chlorella vulgaris and Dunaliella salina. By investigating the retention degree versus contact time from Langmuir and Freundlich biosorption isotherms, kinetic investigations and FTIR spectra it was found that the biosorption process was greater for Chlorella vulgaris than for Dunaliella salina. A new kinetics method is proposed to establish the reaction order concerning the biosorption process of uranyl ions on these biomasses.

Investigation of 7-((dioctylamino)methyl)quinoline-8-ol for uptake and removal of uranyl ions

A new 8-hydroxyquinoline derivative extractant was synthesized via the Mannich reaction from a secondary amine. Various analytical techniques (1H, 13C NMR, FTIR, mass spectroscopy) were used to characterize our product. The use of this new extractant for the uptake and removal of uranyl ions in aqueous solution was investigated. Conditions for an effective sorption were optimized with respect to different experimental parameters in batch process. The results showed that the extraction rate increases for solutions with a pH in the range [0.65–1.13]. The total sorption capacity was 105 (mg g−1) under optimum experimental conditions. The extraction of UO2 2+ was found to be quantitative (100 %) at initial uranyl concentration less than or equal to 41.59 mg/L. Thermodynamic parameters showed the adsorption of an endothermic process and a spontaneous nature, respectively.

Preparation and uranyl ion extraction studies of calix[4]arene-based magnetite nanoparticles

The article describes both syntheses of diamide derivatives of p-tert-butylcalix[4]arene (3a and 3b) and their immobilization onto [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane-modified Fe3O4 magnetic nanoparticles to obtain calixarene-based magnetic nanoparticles (CB-MNs). All prepared magnetic nanoparticles (CB-MNs) were characterized by a combination of elemental analysis, FTIR, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The studies regarding the removal of uranyl ion from the aqueous solutions have been carried out both in liquid–liquid and in solid–liquid extraction studies. The results show that the prepared magnetic nanoparticles (4a and 4b) are better removing uranyl ion than the precursor calix[4]arene derivatives (3a and 3b).

Preparation of ethylenediamine-modified magnetic chitosan complex for adsorption of uranyl ions

Ethylenediamine-modified magnetic chitosan (EMMC) complex was developed as a novel magnetic adsorbent for the removal of uranyl ions. XRD spectrum indicated that the magnetic particles were pure Fe 3O 4 with a spinel structure, and the binding of chitosan did not result in a phase change. IR analysis demonstrated that Fe 3O 4 particles were successfully bounded by chitosan and more amino groups appeared in the EMMC samples. EMMC was found to be quite efficient to adsorb uranyl ions at pH 2–7. Equilibrium was established within 30 min, and the kinetic experimental data properly correlated with the pseudo-second-order kinetic model, indicating that the chemical sorption is the rate-limiting step. The adsorption data could be best interpreted by the Sips model with a maximum adsorption capacity of 82.83 mg U g −1. The EMMC can be regenerated with high efficiency, suggesting that this adsorbent is satisfactory to reuse uranyl ions.

Magnetic biosorbent for removal of uranyl ions

In this work magnetic biosorbent, which consisted of sugarcane bagasse as polymeric matrix with magnetite nanoparticles, was prepared. This magnetic composite has the purpose to remove uranyl ions from aqueous effluents. This magnetic biosorbent have presented superparamagnetic properties. Variables of adsorption process of uranyl ions by magnetic biosorbent in nitric solutions were investigated, such as, time required for the uranium-magnetic bagasse biosorbent equilibrium in the interval from 20–90 min, pH in the intervals from 2–5 and 10, stirring speed from 240–500 rpm and biosorbent dose from 2–25 g L –1 were investigated. Equilibrium isotherm was verified according to the Langmuir and Freundlich adsorption isotherm models.

Equilibrium adsorption isotherm of U(VI) at pH 4 and pH 5 onto synthetic magnetite nanoparticles

The adsorption features of synthetic magnetite nanoparticles have been investigated for removal of uranyl ions from nitric solutions. These magnetic nanoparticles can be used to adsorb contaminants in wastewater and can subsequently be removed from the medium by a magnetic process because of their superparamagnetic behaviour. The magnetite nanoparticles were synthesised by simultaneous precipitating of Fe2+ and Fe3+ ions in a NaOH solution. Batch experiments were carried out to investigate the adsorption of UO22+ ions from nitric solution, pH 4 and 5, onto magnetic nanoparticles. Two minutes of application of a magnetic field were sufficient for removing the magnetite nanoparticles from the liquid medium. Equilibrium adsorption isotherm was evaluated using Freundlich and Langmuir models. The adsorption was between 40% and 80% under conditions studied.

Selective adsorption of uranyl ion on ion-imprinted chitosan/PVA cross-linked hydrogel

An interpenetration network (IPN) ion-imprinting hydrogel (IIH) was synthesized using uranyl ions as template for adsorption and removal of uranyl ions from aqueous solutions. The IIH was obtained via cross-linking of blended chitosan/polyvinyl alcohol (PVA) using ethylene glycol diglycidyl ether (EGDE). The ability of the IIH to adsorb and remove uranyl ions from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed in the pH range of 5.0–6.0. The adsorption process could be well described by both the Langmuir and Freundlich isotherms and the maximum adsorption capacity calculated from Langmuir equation was 156 mg/g. Equilibrium was achieved within 2 h. The kinetic data, obtained at optimum pH 5.0 could be fitted with to a pseudo-second order equation. The selectivity coefficient of uranyl ion and other metal cations on IIH indicated an overall preference for uranyl ions which was much higher compared with the non-imprinted hydrogel. This suggests that the IIH is a promising sorbent material for the selective removal of uranyl ions from aqueous solutions.

Effect of pH on the Adsorption of Uranyl Ions by Peat Moss

The removal of uranyl ions from aqueous solutions with peat moss was investigated by batch methods. The effects of factors such as the pH, ionic strength, contact time, peat moss dosage and humic acid concentration on uranyl ion adsorption were studied. The results indicated that the adsorption of uranyl ions onto peat moss increased with increasing pH within the range 2-6, with higher humic acid concentrations and with decreasing ionic strength. The kinetics of the adsorption process were well described by the Elovich equation, while the equilibrium adsorption isotherm was fitted reasonably well by the Freundlich adsorption model. The calculated fractal dimension of granular peat moss was 2.3384.

Synthesis and Characterization of a Bentonite-Alginate Microspherical Adsorbent for Removal of Uranyl Ions from Aqueous Solutions

A novel microspherical adsorbent for the removal of uranium from aqueous solutions was developed by immobilizing of natural bentonite in the polymeric matrix of calcium alginate. Different uptake properties of the prepared microspheres were examined using batch, stirred and column methods. The adsorbent showed high affinity toward uranium ions, especially at pHs above 3. Major uptake mechanisms included ion exchange, chelating of the (UO2)2+ ions to the ‒OH groups of alginate, and surface complexation with bentonite. Surprisingly, the capacity of microspheres was higher than both its constituents, revealing that a synergetic effect occurs. Adsorption kinetics was controlled by slow chemical reaction of ions with bentonite, and it obeyed a shrinking core model. Also a pseudo-second order chemical reaction fairly fitted the kinetics data. The synthesized microsphrese, in addition to cost efficiency, showed a relatively good column performance and high durability and reusability.

Hydroxy- and alkoxy-bridged dinuclear uranyl–Schiff base complexes: hydrolysis, transamination and extraction studies

The reaction of uranyl nitrate with 1,3-bis(salicylideneamino)-2-propanol (H(3)L1) and 1,3-bis(3,5-di-tert-butylsalicylideneamino)-2-propanol (H(3)L2) in the presence of triethylamine (Et(3)N) yielded hydroxy- and alkoxy-bridged dinuclear complexes; [(UO(2))(2)(L1)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)) and [(UO(2))(2)(L2)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)). The crystal structures of .(DMF)(2) and .(DMF)(2) exhibit an unsymmetrical central U(2)O(2) core involving bridging alkoxy- and hydroxy-oxygen atoms. The geometry around the uranium center in .(DMF)(2) and .(DMF)(2) is that of a distorted pentagonal bipyramid with the solvent molecule occupying the fifth coordination site. The flexible nature of the ligand backbone is more pronounced in .(DMF)(2) compared to .(DMF)(2), yielding two molecules per unit cell in different conformations. Under similar reaction conditions, using ethylenediamine as a base, the respective Salen-based uranyl compounds, [UO(2)(Salen)(MeOH)] () and [UO(2)(Bu(t)(2)-Salen)(MeOH)] () are obtained due to transamination of the ligand backbone. Complexes .(MeOH)(2) and .(MeOH)(2) when reacted with an excess of ethylenediamine failed to yield the respective Salen-based complexes, and , respectively. The new compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Hydrolysis of .(MeOH)(2) and .(MeOH)(2) in the pH range 1-14 was studied using UV-Vis spectroscopy and compared with the hydrolysis of and [UO(2)(Salophen)(MeOH)] (). A two-phase extraction study suggests quantitative removal of uranyl ions from the aqueous phase at higher pH conditions.

Borosilicate glasses modified with organic ligands: A new selective approach for the removal of uranyl ion

Barium borosilicate glass was found to have high uptake capacity for many cations. To improve its selectivity, surface modification was carried out. In order to make the glass selective towards uranyl ion, organic ligands like tri- n-octylphosphine oxide (TOPO) and 8-hydroxy quinoline (Oxine) were used. It was observed that the surface modification resulted in the change in uptake property of the glass. The uptake process was faster and within 5 h, 90% of the uranyl ion could be taken up from a 0.01 mM solution. With use of the modified barium borosilicate glass and EDTA as masking agent, uranyl ion could be selectively removed from mixtures of cations.

Application of polymer-modified nanoporous silica to adsorbents of uranyl ions

The surface modification of nanoporous silicas (MSU-H) of submicron-scale particle size with polyethyleneimine (PEI), polyacrylic acid (PAA), and carboxymethylated polyethyleneimine (CMPEI) was carried out for the extraction of uranyl ions. Adsorption behaviors of uranyl ions onto the polymer-modified silicas, denoted as PEI/MSU-H, PAA/MSU-H and CMPEI/MSU-H, were examined in batch experiments. In 0.05mM UO22+ solution, it was found that the nearly complete removal of uranyl ions can be achieved by the CMPEI-modified MSU-H (CMPEI/MSU-H). Especially, the CMPEI/MSU-H exhibited significantly high distribution coefficient value (Kd=2.30×106). In concentrated UO22+ solution (ca. 1mM), uranium-uptake capacities onto the three polymer-modified nanoporous silicas were in the following order: CMPEI/MSU-H>PAA/MSU-H>PEI/MSU-H. It is noteworthy that CMPEI/MSU-H showed excellent uranium-uptake capacity (124mg-U/g-adsorbent), based on the total weight of polymer and silica. In addition, the loading stability of uranium on the adsorbent was examined with time. It was observed that about 15% of uranium was discharged from CMPEI/MSU-H in a day and additional 5% uranium was released with a relatively slow desorption rate in 12 days.

Removal of Toxic Uranium from Synthetic Nuclear Power Reactor Effluents Using Uranyl Ion Imprinted Polymer Particles

Major quantities of uranium find use as nuclear fuel in nuclear power reactors. In view of the extreme toxicity of uranium and consequent stringent limits fixed by WHO and various national governments, it is essential to remove uranium from nuclear power reactor effluents before discharge into environment. Ion imprinted polymer (IIP) materials have traditionally been used for the recovery of uranium from dilute aqueous solutions prior to detection or from seawater. We now describe the use of IIP materials for selective removal of uranium from a typical synthetic nuclear power reactor effluent. The IIP materials were prepared for uranyl ion (imprint ion) by forming binary salicylaldoxime (SALO) or 4-vinylpyridine (VP) or ternary SALO-VP complexes in 2-methoxyethanol (porogen) and copolymerizing in the presence of styrene (monomer), divinylbenzene (cross-linking monomer), and 2,2'-azobisisobutyronitrile (initiator). The resulting materials were then ground and sieved to obtain unleached polymer particles. Leached IIP particles were obtained by leaching the imprint ions with 6.0 M HCl. Control polymer particles were also prepared analogously without the imprint ion. The IIP particles obtained with ternary complex alone gave quantitative removal of uranyl ion in the pH range 3.5-5.0 with as low as 0.08 g. The retention capacity of uranyl IIP particles was found to be 98.50 mg/g of polymer. The present study successfully demonstrates the feasibility of removing uranyl ions selectively in the range 5 microg - 300 mg present in 500 mL of synthetic nuclear power reactor effluent containing a host of other inorganic species.

A simplified method to estimate kinetic and thermodynamic parameters on the solid–liquid separation of pollutants

The aim of the present study was to propose a simplified experimental–theoretical method for estimating the kinetic and thermodynamic parameters for the solid–liquid separation of pollutants by using kinetic studies with batch reactors, i.e., the removed quantity of dissolved ion as a function of time at different initial concentration. This method was applied to the removal of uranyl ion (UO 2+ 2) from aqueous solutions onto synthetic manganese oxide (birnessite). The pseudo-second-order kinetics and one-site saturation models were proposed to fit the experimental and calculated data, the fitting parameters being estimated by nonlinear regression, using the least-squares method. For initial concentration range 0.2–11.8 μM, the results showed that the uranyl removal process in dispersed batch reactors can be efficiently modeled by the proposed models. Then, several kinetic and thermodynamic parameters were calculated, such as maximal removed quantity of uranyl, q r , max , half-removal time, t 1 / 2 , initial rate of uranyl-ion removal, v 0 , initial uranyl-removal coefficient, K, maximal rate of uranyl removal, v 0 , max , mass transfer coefficient, D transfer , equilibrium Langmuir constant, K L , and constant separation factor, K s . These parameters make it possible to demonstrate that the removal of U onto birnessite is favorable, and that the maximum surface coverage of the uranyl ions represents about 3% of vacant sites in the Mn layer.

Adsorption of Uranyl Ions into Poly(Acrylamide‐co‐Acrylic Acid) Hydrogels Prepared by Gamma Irradiation

Acrylamide (AAm)/Acrylic Acid (AAc) copolymers have been prepared by gamma irradiation of binary mixtures at three different compositions where the acrylamide/acrylic acid mole ratios varied around 15, 20, and 30%. Threshold dose for 100% conversion of monomers into hydrogels was found to be 8.0 kGy. Poly(Acrylamide‐co‐Acrylic Acid) (poly(AAm‐co‐AAc)) hydrogels have been considered for the removal of uranyl ions from aqueous solutions. Swelling behavior of these hydrogels was determined in distilled water at different pH values and in aqueous solutions of uranyl ions. The results of swelling tests at pH 8.0 indicated that poly(AAm‐co‐AAc) hydrogel, containing 15% acrylamide showed maximum % swelling. Diffusion of water and aqueous solutions of uranyl ion into hydrogels was found to be non‐Fickian in character and their diffusion coefficients were calculated. The effect of pH, composition of hydrogel, and concentration of uranyl ions on the adsorption process were studied at room temperature. It was found that one gram of dry poly(AAm‐co‐AAc) hydrogel adsorbed 70–320 mg and 70–400 mg uranyl ions from aqueous solutions of uranyl nitrate and uranyl acetate in the initial concentration range of 50–1500 mg UO2 2+L−, depending on the amount of AAc in the hydrogels, respectively. Adsorption isotherms were constructed for poly(AAm‐co‐AAc)–uranyl ion system indicating an S type of adsorption in the Giles classification system. It is concluded that crosslinked poly(AAm‐co‐AAc) hydrogels can be successfully used for the removal of uranyl ions from their aqueous solutions.

Removal of uranyl ions from residual waters using some algae types

This paper deals with a study on the bioaccumulation of uranyl ions resulted from residual effluents by means of some microbiological collectors: Scenedesmus quadricauda, Anabaena karakumica, Calothrix brevissima, Penicillinium sp, as well as the Glucide extract of Porphyridium cruentum, under various experimental conditions. The retaining degree of the bioaccumulated uranyl ions, as well as the leaching degree, in HCl and H2O media, of the same ions previously retained on algae were established. The retaining degree decreases in the serie: Scenedesmus quadricauda >Anabaena karakumica >Penicillinium sp>Calothrix brevissima. The leaching effect of bioaccumulated uranyl ions is higher in hydrochloric acid than in water.

The use of Escherichia coli bearing a phoN gene for the removal of uranium and nickel from aqueous flows.

A Citrobacter sp. originally isolated from metal-polluted soil accumulates heavy metals via metalphosphate deposition utilizing inorganic phosphate liberated via PhoN phosphatase activity. Further strain development was limited by the non-transformability of this environmental isolate. Recombinant Escherichia coli DH5 alpha bearing cloned phoN or the related phoC acquired metal-accumulating ability, which was compared with that of the Citrobacter sp. with respect to removal of uranyl ion (UO2(2+)) from dilute aqueous flows and its deposition in the form of polycrystalline hydrogen uranyl phosphate (HUO2PO4). Subsequently, HUO2PO4-laden cells removed Ni2+ from dilute aqueous flows via intercalation of Ni2+ into the HUO2PO4 lattice. Despite comparable acid phosphatase activity in all three strains, the E. coli DH5 alpha (phoN) construct was superior to Citrobacter N14 in both uranyl and nickel accumulation, while the E. coli DH5 alpha (phoC) construct was greatly inferior in both respects. Expression of phosphatase activity alone is not the only factor that permits efficient and prolonged metal phosphate accumulation, and the data highlight possible differences in the PhoN and PhoC phosphatases, which are otherwise considered to be related in many respects.

Selective recovery of uranium(VI) from aqueous acid solutions using micellar ultrafiltration

Preconcentration and removal of uranyl ions from aqueous solutions were achieved by using micellar-enhanced ultrafiltration with complexing micellar aggregates composed of Triton X-100 and different hydrophobic ligands. Derivatives of 4-aminosalicylic acid (PAS) and of 1-(2-pyridylazo)-2-naphthol (PAN) having tuned alkyl chains were used as suitable chelating agents. The selective recovery of uranyl from acid samples containing also SrII and CdII is possible using the multi-step ultrafiltration approach with the PAN derivatives, whereas effective uranyl retention can be obtained with salicylates only in neutral to basic media.

Enhancement of uranium bioaccumulation by a Citrobacter sp. via enzymically‐mediated growth of polycrystalline NH4UO2PO4

AbstractThe objective of this work was to study the effect of pH and ionic matrix on product release and on the removal of uranyl ion by a Citrobacter. sp phosphatase enzyme‐catalysed reaction. An improvement in the efficiency of uranyl removal was obtained by incorporating ammonium acetate (NH4Ac) into the solution. It was confirmed using X‐ray diffraction (XRD), and other analytical techniques, that the insoluble, cell‐bound product was NH4UO2PO4.