Development of New Cationic Exchangers for the Recovery of Uranium (VI) from Concentrated Phosphoric Acid

The extraction of uranium (VI) from 5.3 mol.L^?1 phosphoric acid with a series of phosphoric, phosphinic, dithiophosphoric, or dithiophosphinic acid derivatives (0.5 mol.L^?1) in mixture with 0.125 mol.L^?1 TOPO in Isane IP 185 has been investigated. In the frame of the present work, eight acidic phosphorus and thiophosphorus compounds have been synthesized: bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(1,3-bis-(butylthio)propan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid, bis(1-butoxyheptan-2-yl) phosphoric acid, bis(undecan-6-yl) phosphoric acid, bis(2-(1,3-dibutoxypropan-2-yloxy)ethyl) phosphoric acid, bis(3-butoxy-2-(butoxymethyl)-2-methylpropyl) phosphinic acid, bis(1,3-dibutoxypropan-2-yl) dithiophosphoric acid. The properties of these molecules in mixtures with TOPO have been compared with those of other extractants such as bis(2-ethylhexyl) phosphoric acid, bis(2-ethylhexyl) dithiophosphoric acid, bis(2-ethylhexyl) phosphinic acid, Cyanex® 272, and Cyanex® 301. The replacement of phosphoric acid-type extractant by their phosphinic homologues dramatically decreases the affinity for uranium (VI) whereas the replacement of the phosphoric and phosphinic acid-type extractants by their dithio homologues affects positively the distribution coefficient of uranium (VI). It also appears that the steric hindrance effect is responsible for a significant decrease of the distribution coefficient of uranium (VI). Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.     

Influence of pH on U(VI) Adsorption using a Thermally-Treated Mg-Al Hydrotalcite and a Natural Zeolite in a Batch System

The capacity of a calcined hydrotalcite and a natural zeolite to remove U(VI) chemical species from both acidic and basic aqueous systems has been investigated. The U(VI) uptake by the calcined hydrotalcite and the natural zeolite was determined to be from 5 to 200 µmolmL^?1 and from 2 to 10 µmolmL^?1, respectively. Uranium was measured using UV-Vis spectroscopy in the remaining solutions. The U(VI) adsorption of both materials was higher in the acidic aqueous system. Independent of the pH of the aqueous media, the [UO₂(CO₃)₃]^4? species play an important role in the regeneration of the original crystalline structure of the HT.     

Comparative Evaluation of Tri-n-butyl Phosphate (TBP) and Tris(2-ethylhexyl) Phosphate (TEHP) for the Recovery of Uranium from Monazite Leach Solution

Separation of U(VI) from Th(IV) and rare earth elements (REEs) present in monazite leach solution (nitric acid medium) has been studied using tris(2-ethylhexyl) phosphate (TEHP) and tri-n-butyl phosphate (TBP) dissolved in n-paraffin as solvents under varying experimental conditions such as nitric acid, extractant and metal ion concentrations etc. There is an increase in distribution ratio of U(VI) (D _U ) with increase in aqueous phase acidity up to 5 M HNO₃ beyond which a decrease is observed. Typically for 1 × 10^?3 M U(VI), the D_U values increase from 8 (0.5 M HNO₃) to 80 (5 M HNO₃) for 1.1 M TEHP, and from 2 (0.5 M HNO₃) to 43 (5 M HNO₃) for 1.1 M TBP in n-paraffin. The separation factors of U(VI) (β: D_U/D_M) over metal ions (M) such as Th(IV) and Y(III) (chosen as a representative of heavy REEs) are better for TEHP than TBP at all nitric acid concentrations. Batch solvent extraction data have been used to construct the McCabe-Thiele diagrams for the recovery of U(VI) employing TEHP as the extractant. A process flow sheet has been proposed with 0.2 M TEHP in n-paraffin as solvent for the recovery of U(VI) from simulated monazite leach solution in HNO₃ medium.     

Extraction of Uranium(VI) and Thorium(IV) from Nitric Acid Solution by N,N,N′,N′ – Tetraoctylglutaricamide

Synthesis and characterization of N,N,N′,N′-tetraoctylglutaricamide (TOGA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO₃ concentration, equilibration time, temperature, and types of diluents) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·1.0TOGA and Th(NO₃)₄·1.5TOGA. The apparent equilibrium constant of U(VI) and Th(IV) extraction determined are 3.35 ± 0.03 L³/mol³ and 1.87 ± 0.01 L⁵/mol⁵ at 298 ± 1 K. Thermodynamic parameters such as the free energy(ΔG), enthalpy(ΔH), and entropy(ΔS) changes associated with the extraction processes could be evaluated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.     

Simultaneous Extraction of Neodymium and Uranium using Hollow Fiber Supported Liquid Membrane

Simultaneous extraction of neodymium and uranium ions from aqueous nitrate media was investigated using hollow fiber supported liquid membrane (HFSLM). The organic phase supported in the membrane pores consisted of extractant N,N,N’,N’-tetraoctyl diglycolamide (TODGA), phase modifier isodecanol, and diluent n-dodecane. Experimental results suggest that there is competition between neodymium and uranium ions for complexation with TODGA. The initial rate of extraction of Nd³⁺ ions was found to be approximately six times to that of UO₂²⁺ ions. Experimental data was explained by a mathematical model for simultaneous transport of two metal ions. The model results were found to be in good agreement with the experimental data when the diffusivities of neodymium-TODGA complex (D_nm) and uranium-TODGA complex (D_um) in the membrane pore are 1.1 x 10^?11 and 4 x 10^?12 m²/s, respectively.     

Unmodified SBA-15 adsorbents for the removal and separation of Th(IV) and U(VI) ions: the role of pore channels and surface-active sites

ABSTRACT

The removal of Th(IV) and U(VI) by calcinated, non-calcinated, and methyl grafted SBA-15 (abbreviated as SBA-15, SBA-15-NC and SBA-15-MG, correspondingly) were compared to elucidate the role of pores and surface adsorption sites on SBA-15 adsorbents. It was proposed that the contribution of pores and surface-active sites of SBA-15 increases its higher adsorption capacity with respect to the other examined adsorbents. The kinetic studies revealed that the adsorption and also desorption occurred initially on the surface and then to the pores. Adsorption/desorption of the ions into pores was occurred with slow kinetics.     

Removal of Trace Concentrations of Heavy Metals Using Complexing Ion‐Exchange Resins

Abstract

Oak Ridge National Laboratory is examining potential new technologies for treating radiologically‐contaminated process wastewater. The current treatment facility is aging and is optimized to remove ⁹⁰Sr, but future wastewaters are likely to contain mostly activated metals, such as ⁵¹Cr and ⁶⁴Cu. Other low‐volume wastewaters may contain trace concentrations of Hg and U. Complexing ion‐exchange resins and other specialized sorbents were tested for removing trace concentrations of heavy metals. Short‐term column tests and batch loading tests were conducted using a surrogate wastewater and various sorbents. These tests showed that metal uptake was very rapid, and that good removal and relatively high loadings could be achieved from a very dilute wastewater surrogate. Forager M‐TU (Dynaphore, Inc.) showed the best overall results, removing 91.9% of the Cr, 99.3% of the Cu, >99.7% of the Hg, and >99.9% of the U with a contact time of 120 seconds in a short‐term column test.     

酸浸及紫外诱变对氧化亚铁硫杆菌浸矿的影响

利用从湖北省大冶市铜山口矿区的酸性矿坑水中选育的氧化亚铁硫杆菌（Thiobacillus ferrooxidans,以下简称T.f菌）对该矿区的铁矿进行了浸矿研究。结果表明：未经酸浸处理的矿粉,对体系pH值的影响较大,从而影响T.f菌的生长,进而影响浸矿效果;经过酸浸处理的矿粉,在整个浸矿过程中,体系pH值相对恒定,T.f菌生长良好;对混合菌群进行单次紫外诱变,未能明显提高浸矿能力。     

磁性交联壳聚糖对水溶液中铀(Ⅵ)离子的吸附行为

采用纳米Fe₃O₄作为磁流体包埋、戊二醛和硫脲进行交联壳聚糖,制备磁性交联壳聚糖（TTG-MCTS）。红外光谱（FTIR）和X射线能谱（EDS）分析结果表明,壳聚糖改性后,吸附能力得到提高,铀(Ⅵ)成功地被吸附在TTG-MCTS上。系统研究了溶液pH值、铀(Ⅵ)初始浓度及振荡时间对吸附容量的影响,继而得到最佳工艺条件。吸附过程用Langmuir等温式拟合优于用Freundlich等温式,最大吸附容量为161.3 mg·g^-1。较之拟一级动力学模型,拟二级动力学模型能更好地拟合实验数据。     

三江云南段燕山期花岗岩地球化学特征与铀成矿潜力分析

在系统研究三江云南段燕山期花岗岩岩石地球化学特征基础上,将相关岩体的岩体地质与地球化学特征与华南产铀花岗岩的进行对比,进而对三江云南段燕山期花岗岩的铀成矿潜力进行讨论。结果表明,三江云南段燕山期花岗岩具有富硅、富碱、铝过饱和、低钙、低暗色组分等特征,与华南产铀花岗岩的特征相似,成矿条件较好,具有一定的铀成矿前景。