Use of Amidoxime-Group-Containing Adsorbent for the Recovery of Uranium and Other Elements from Phosphoric Acid Solution

Abstract

An amidoxime-group-containing fibrous adsorbent which was made by the radiation-induced grafting of acrylonitrile onto a synthetic fiber was applied to the recovery of uranium and other elements (V, Ti, Fe, etc.) from phosphoric acid solution of a fertilizer plant. The adsorption amount of these elements increased in proportion to the concentration of amidoxime groups introduced in the adsorbent. The distribution of the metals adsorbed in 24 h was homogeneous in the adsorbent containing more than 4.9 meq/g amidoxime groups while it was limited to the surface region of the adsorbent containing 1.5 meq/g amidoxime groups. The rise in the pH of the solution brought about by adding sodium hydroxide produced a maximum amount of adsorption at pH = 3. The concentration factors for U, V, Ti, and Fe were 2.8 × 10², 8.6 × 10³, 4.2 × 10³, and 6.1 × 10², respectively.     

Recovery of Uranium from Seawater

Abstract

Seawater contains various elements in solution. Deuterium, lithium, and uranium are the important ingredients for energy application at present and in the future. This paper deals with the recovery of uranium from seawater, with emphasis on the development of an adsorbent with high selectivity and rate of adsorption for uranium.

Polyacrylamidoxime chelating resins were synthesized from various co-polymers of acrylonitrile and cross-linking agents. The resulting resins with the chelating amidoxime group showed selective adsorption for uranium in seawater. The amount of uranium adsorbed from seawater at room temperature reached 3.2 mg/g resin after 180 days.

Polyacrylamidoxime fiber, which was prepared from polyacrylo-nitrile fiber and hydroxylamine, showed a high rate of adsorption for uranium. The polyacrylamidoxime fiber conditioned with 1 M HCl and 1 M NaOH adsorbed 4 mg U/g fiber from seawater in ten days.     

Effect of Shape and Size of Amidoxime-Group-Containing Adsorbent on the Recovery of Uranium from Seawater

Abstract

An amidoxime-group-containing adsorbent for the recovery of uranium from seawater was synthesized by radiation-induced graft polymerization of acrylonitrile onto polypropylene fiber of round and cross-shaped sections. The tensile strength and elongation of the synthesized adsorbent, both of which were one-half those of the raw material, were not affected by the shape of the fiber. The deterioration of the adsorption ability induced by immersing the adsorbent in HC1 was negligible because of the short immersion time required for the desorption with HC1. The concentration factors for uranium and transition metals in 28 days were in the order of 10⁵, while those for alkali metals and alkaline earth metals were in the order 10^?1-10¹. The recovery of uranium with the cross-shaped adsorbent was superior to that of the round-shaped one. XMA line profiles show that the distribution of uranium is much restricted to the surface layer when compared with that of alkaline earth metals. Diminishing the diameter or increasing the surface area was effective for increasing the adsorption of uranium.     

A New Type of Amidoxime-Group-Containing Adsorbent for the Recovery of Uranium from Seawater. III. Recycle Use of Adsorbent

Abstract

An amidoxime-group-containing adsorbent for recovering uranium from seawater was made by radiation-induced graft polymerization of acrylonitrile onto polymeric fiber, followed by amidoximation. Uranium adsorption of the adsorbent contacted with seawater in a column increased with the increase in flow rate, then leveled off. The relationship between uranium adsorption in a batch process and the ratio of the amount of seawater to that of adsorbent was found to be effective in evaluating adsorbent contacted with any amount of seawater. The conditioning of the adsorbent with an alkaline solution at higher temperature (80°C) after the acid desorption recovered the adsorption ability to the original level. This made it possible to apply the adsorbent to recycle use. On the other hand, the adsorbent conditioned at room temperature or that without conditioning lost adsorption ability during recycle use. The increase in water uptake was observed as one of the physical changes produced during recycle use of the alkaline-conditioned adsorbent, while the decrease in water uptake was observed with the unconditioned adsorbent. The IR spectra of the adsorbent showed a probability of reactions of amidoxime groups with acid and alkaline solutions, which can explain the change in uranium adsorption during the adsorption-desorption cycle.     

Desorption of Uranium from Amidoxime Fiber Adsorbent

Abstract

An amidoxime fibrous adsorbent is contacted with uranium-enriched seawater (10 ppm); about 10 mg uranium is loaded per 1 g dry fiber. Then the rate and yield of uranium desorption from the fiber are determined with various eluents. Acid solutions are superior to alkali carbonate solutions as eluents. With a 0.1 mol·L^?1 HCl solution, desorption is completed in 2 hours regardless of the presence of uranium in the leaching solution up to 15 ppm (? 6 × 10^?5 mol·L^?1). Serial operation of the adsorption-desorption cycle four times does not affect desorption efficiency, but the addition of heavy metal ions to the eluent at a level of 1.8 × 10^?3 mol·L^?1 significantly decreases desorption efficiency.     

Recovery of uranium from seawater V. Preparation and properties of the macroreticular chelating resins containing amidoxime and other functional groups

We have synthesized macroreticular chelating resins containing amidoxime groups from acrylonitrile (AN)-divinylbenzene (DVB)-alkyl acrylate, alkyl methacrylate, or vinylpyridine (VPy) copolymer beads. It was found that the chelating resin (RNMH)-containing amidoxime groups prepared from AN-DVB-methyl acrylate (MA) indicated the highest adsorption ability for uranium in seawater. Hydroxamic acid and carboxylic groups in addition to amidoxime groups were formed during the reaction of the copolymer beads with a methanol solution of hydroxylamine. The adsorption ability for uranium was greatly influenced by the physical pore structure (macropore) and the pore structure formed by the swelling(micropore). RNMH (RNMH10-10) prepared with 10 mol% of DVB and 10 mol% of MA had the highest adsorption ability and physical stability for uranium. On the other hand, improved adsorption ability for uranium was not observed in the case of the macroporous resins (RNPyH) prepared by the copolymerization of VPy as the basic component. After seawater was passed through the column packed with RNMH10-10 at a space velocity (SV) of 180 h^?1 (up-flow) for 10 days, the amount of uranium adsorbed on the resin was about 100 mg/dm³-R and 260 mg/kg-R.     

Desorption of Uranium Recovered with Fibrous Amidoxime Adsorbent Shaped into Balls

Abstract

Amidoxime fiber synthesized with a commercial PAN fiber was packed in 2 cm-diameter spherical shells made of plastic net. The adsorbent balls were then packed in a cage through which seawater passed. This shape of adsorbent increased the contact efficiency between adsorbent and seawater but might decrease the desorption rate of uranium adsorbed in the balls. The rate of desorption from 2 cm-diameter adsorbent balls packed in a column was nearly equal to the value obtained with completely dispersed amidoxime fiber, however, when the eluent velocity through the balls was higher than 2–4 cm·s^?1 and the void fraction in the balls was higher than 0.8. Most of the liquid held in the balls was removed with a light centrifugation.     

Simulation of Adsorption of Uranium from Seawater Using Liquid Film Mass Transfer Controlling Model

Abstract

A liquid film mass transfer control model was applied to the batch adsorption of uranium from seawater with an amidoxime-group-containing polymeric adsorbent made by the radiation-induced grafting method. The adsorption amount was calculated by changing two parameters, equilibrium adsorption amount q_o and liquid film mass transfer coefficient k, to obtain the best fit between the observed and calculated values. The index of a Freundlich-type isotherm was obtained as 1.6, which is similar to the previously observed value with hydrous titanium oxide adsorbent. The plot of k vs 1/T provided the activation energy as 10.0 kcal/mol. Both q_o and k showed an approximately first-order dependency on the amidoxime group content in the adsorbent. The simulation made it clear that the increase in k brought about by mixing amidoxime groups with carboxyl groups was due to a synergistic effect of these groups     

Recovery of Uranium from Seawater by Immobilized Tannin

Abstract

Tannin compounds having multiple adjacent hydroxy groups have an extremely high affinity for uranium. To prevent the leaching of tannins into water and to improve the adsorbing characteristics of these compounds, we tried to immobilize tannins. The immobilized tannin has the most favorable features for uranium recovery; high selective adsorption ability to uranium, rapid adsorption rate, and applicability in both column and batch systems. The immobilized tannin can recover uranium from natural seawater with high efficiency. About 2530 μg uranium is adsorbed per gram of this adsorbent within 22 h. Depending on the concentration in seawater, an enrichment of up to 766,000-fold within the adsorbent is possible. Almost all uranium adsorbed is easily desorbed with a very dilute acid. Thus, the immobilized tannin can be used repeatedly in the adsorption-desorption process.     

Kinetics of Adsorption of Uranium on Amidoxime Polymers from Seawater

Abstract

Distributions of uranium adsorbed on amidoxime polymers crosslinked with tetraethyleneglycol dimethacrylate (4EGDM) and/or divinylbenzene (DVB) from seawater were examined by x-ray microanalysis in order to elucidate the diffusion behavior of uranium into the polymer matrix. The uniform distribution of the ligands on the polymers was confirmed by the distribution of Cu(II) adsorbed from copper(II) dichloride solutions. It was found that the distribution of uranium adsorbed is changed significantly by the composition of 4EGDM and DVB. Thus, the polymer crosslinked with 4EGDM exhibits a uniform distribution of uranium; however, as the ratio of DVB to 4EGDM increases, a more predominant distribution of uranium near the periphery of the polymer particle appears and the intensity decreases. This suggests that the adsorption rate of uranium is governed by the diffusion of uranium into the polymer matrix, explaining well the dependence of the adsorption rate on the hydrophilicity of the polymer. On the basis of these results, the diffusion constant of uranium into the polymer matrix was estimated to be 3.3 × 10^?-7 cm²/s.     

Selective Elution of Uranium from Amidoxime Polymer. II

Abstract

A separative elution of uranium from an amidoxime polymer which had been immersed in seawater was examined on its relation with the flow rate of acidic eluent. The elution with 0.5 M HC1 at S.V. ≤ 1 h^?1 or with 1.0 M HCl at S.V. ≤ 3 h^?1, which was started from the elution by 16.5 L/L _p of 0.1 MHCl at S.V. ≤ 3 h^?1, provided an eluate containing more than 80% of uranium adsorbed and separating from other metal ions except Fe(III) and Cu(II). The efficiency of uranium elution was hardly affected by the scale of the system employed. Acid consumption, which occurred predominantly in the elution with 0.1 M HCl, was ～1.4 mol/L _p . The results suggest that this elution method is promising in the recovery of uranium from seawater.     

Recovery of uranium by tannin immobilized on matrices which have amino group

Tannin, which contains polyhydroxy groups, has a high affinity for uranium. Various tannin–protein complexes were prepared to develop new adsorbents for uranium recovery from seawater. Albumin tannate has a high ability to adsorb uranium from seawater. Tannin was immobilized on matrices which have multiple active amino groups, such as aminopolystyrene and poly(vinyl-4,6-diamino-s-triazine)—poly VT. Of these complexes, tannin immobilized on poly VT adsorbed uranium most efficiently from seawater and highly selectively from a solution containing various heavy metals; the uranium adsorption was very rapid and was pH dependent. This adsorbent therefore appears to have potential for use in a commercial process for uranium recovery from seawater or from uranium-containing waste water.     

Kinetics of Adsorption of Uranium from Seawater by Humic Acids

Abstract

The kinetics of the adsorption of uranium from seawater by humic acids fixed onto a polymer matrix was measured in a fluidized bed as a function of the grain size of the adsorbent and the flow velocity of the seawater. The adsorption rate was found to be governed by the diffusion of the uranium ions through the hydrodynamic surface layer of the adsorbent which is always formed in laminar flows of liquids. The measured rate constants are interpreted in terms of effective diffusion coefficients of 3.6 × 10^?5 cm²/s for uranyl ions and 1.8 × 10^?5 cm²/s for tricarbonatouranate ions in the surface layer. As a consequence of this kinetic behavior, the geometry of the adsorbent as well as the velocity of the water flow are relevant parameters for the amount of adsorbent needed for a projected extraction rate. This conclusion applies to all adsorption processes where diffusion through the hydrodynamic layer is the rate-determining kinetic step.     

Extraction of Uranium from Seawater Using Magnetic Adsorbents

Abstract

A new process for the extraction of uranium from seawater was developed. In the process, uranium adsorption is effected using powdered magnetic adsorbents; the adsorbents are then separated from seawater using magnetic separation technology. This process is superior to a column method using a granulated hydrous titanium oxide adsorber bed in the following ways: (1) a higher rate of adsorption is realized because smaller particles are used in the uranium adsorption; and (2) blocking, which is inevitable in an adsorber bed, is eliminated.

The composite hydrous titanium-iron oxide as a magnetic adsorbent having high uranium adsorption capacity and magnetization can be prepared by adding urea to a mixed solution of titanium sulfate and ferrous sulfate. Adsorption and desorption of uranium and the removal of the adsorbent using a small-scale uranium extraction plant (about 15 m³/d) is reported, and the feasibility of uranium extraction from seawater by this process is demonstrated.     

高氟高氯含铀废水中偕胺肟基改性聚丙烯腈纤维螯合铀的研究

以聚丙烯腈纤维（PANF）为基体与盐酸羟胺反应制得偕胺肟基改性纤维（AO-PANF）,并通过扫描电镜、红外光谱和批次吸附,探究了AO-PANF对高氟高氯含铀废水中铀的螯合行为。结果表明,偕胺肟化反应将PANF中的氰基成功转化为偕胺肟基团,转化率随盐酸羟胺浓度增加而增大,氰基转化率为22.34%时,AO-PANF对铀的吸附量最大。随废水pH增加,AO-PANF对铀的吸附量先增大后减小,pH为5时,其值最大。F^-和Cl^-浓度变化对AO-PANF的吸附量影响较小。当处理100 ml铀初始浓度为100 mg·L^-1,pH为5的废水,温度为45℃,吸附剂投加量为0.40 g时,转化率为22.34%的AO-PANF对铀的吸附量为19.53 mg·g^-1,3 h左右吸附达到平衡。AO-PANF通过偕胺肟基团中-NH₂与废水中UO₂F₄^2-螯合实现对铀的吸附。该吸附过程符合Freundlich等温吸附模型和准二级动力学方程。研究表明AO-PANF可以有效地螯合高氟高氯含铀废水中的铀,具有良好的应用前景。     

Chelating polymer granules prepared by radiation‐induced homopolymerization. II. Characterizations

Characterizations of chelating polymer adsorbent granules, incorporating amidoxime groups based on polyacrylonitrile (PAN), prepared for selective adsorption of uranium and likely other transition metals were studied. PAN was prepared by radiation‐induced polymerization technique and followed by amidoximation reaction. Conversion of PAN into polyacrylamidoxime (PAO) was studied by fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Morphology and thermal properties were also investigated. PAO was investigated in the separation of uranium from iron‐rich silicate rock samples and subjected to x‐ray fluorescence analysis (XRF). Selective adsorption for uranium and low affinity for alkali and alkaline earth metals were observed. The order of selectivity was found to be U ? Cu > Fe > Ni > Cr > V ? Ca > K. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1180–1187, 2006     

Recovery of uranium by tannin immobilized on agarose

Tannin, which is a ubiquitous and inexpensive material, was immobilized on agarose gel to produce an excellent adsorbent for uranium recovery from seawater. Optimal conditions for the immobilization of tannin on agarose gel by both the epichlorohydrin and cyanuric chloride coupling procedures were examined in detail. The resulting immobilized tannin has a highly selective ability to adsorb uranium and applicability in both column and batch systems. This adsorbent can recover uranium from natural seawater with high efficiency. The maximum adsorption capacities were 1850 μg uranium g^?1 adsorbent for the tannin immobilized on agarose gel by the epichlorohydrin coupling procedure and 1062 μg g^?1 adsorbent for that produced by the cyanuric chloride coupling procedure.     

Development of novel adsorbent materials for recovery and enrichment of uranium from aqueous media

A new polymeric adsorbent bearing both hydrophilic groups providing swelling in water and amidoxime groups for chelating with uranyl ions (UO₂²⁺), has been developed and its adsorptive ability for recovering uranium from aqueous media has been investigated. The polymers obtained by irradiating the solution of polyethylene glycol (PEG) in acrylonitrile (AN) are defined as interpenetrating polymer networks (IPNs) and the adsorbent has been obtained by applying the amidoximation reaction to the IPNs with a conversion ratio of ∼ 60%. Kinetics of the conversion reaction of the cyano (CN) group to the amidoxime (HONCNH₂) group has been studied by reacting with hydroxylamine (NH₂OH) solution at a molar ratio of NH₂OH/CN = 1.25 in aqueous media at three different temperatures, 30, 40, and 50°C, for 3–4 days. The degree of amidoximation ratio was determined by UO₂²⁺ ion adsorption and FTIR spectrometry and the UO₂²⁺ ion adsorption values were found by both UV and gamma spectrometry and also by gravimetry. It was found that the polymeric adsorbent has a very high adsorption ability for uranium and quite a good stability in aqueous media. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2475–2480, 1997     

Effect of Ultrasonic Irradiation on the Recovery of Uranium from Seawater with Adsorbents

Abstract

Ultrasonic irradiation is reported to promote chelate formation between metal ions and polymeric ligands in solution (1). It is expected that the recovery of uranium from seawater with adsorbents is affected by ultrasonic irradiation because this process is also based on chelation between the ligands of the adsorbent and uranyl ion in seawater. In the present note, adsorption of uranium from seawater was carried out under ultrasonic irradiation with an amidoxime-group-containing polymeric adsorbent.     

Recovery of uranium from seawater. VI. Uranium adsorption ability and stability of macroporous chelating resin containing amidoxime groups prepared by the simultaneous use of divinylbenzene and ethyleneglycol dimethacrylate as crosslinking reagent

Macroporous chelating resins (RNH-DVB-1G) containing amidoxime groups with various degrees of crosslinking were synthesized by varying the amount of divinylbenzene (DVB) and ethyleneglycol dimethacrylate (1G). It was confirmed that the content of amidoxime group decreased with an increase in the degree of crosslinking. On the other hand, the amount of amidoxime group hydrolyzed by acid treatment showed a tendency to decrease with an increase in degree of crosslinking. From the measurement of specific surface area and pore size distribution, it was found that the macropore of RNH-DVB-1G with the same degree of crosslinking was remarkably affected by the composition of crosslinking reagent (DVB and 1G). The RNH-DVB-1G prepared in the present work were applied to the recovery of uranium from seawater. It was found that the uranium adsorption ability of RNH-DVB-1G with the same degree of crosslinking was remarkably affected by the proportion of DVB and 1G, although each RNH-DVB-1G had the same content of amidoxime group. In the case of RNH-DVB-1G prepared with 25 mol% of crosslinking reagent, the resin prepared with 10 mol% of DVB and 15 mol% of 1G showed the high adsorption ability for uranium in seawater. These results indicate that the simultaneous use of DVB and 1G contributes to the formation of effective macropore and micropore for recovery of uranium from seawater and the increase of chemical and physical stability.