Solid-Phase Extraction of Trace Amounts of Uranium(VI) in Environmental Water Samples Using an Extractant-Impregnated Resin Followed by Detection with UV-Vis Spectrophotometry

Hindawi Publishing Corporation Journal of Chemistry Volume 2013, Article ID 671564, 10 pages http://dx.doi.org/10.1155/2013/671564 Research Article Solid-Phase Extraction of Trace Amounts of Uranium(VI) in Environmental Water Samples Using an Extractant-Impregnated Resin Followed by Detection with UV-Vis Spectrophotometry Ahmad Hosseini-Bandegharaei, Masoud Sarwghadi, Aliasghar Heydarbeigi, Seyyed Hossein Hosseini, and Mehdi Nedaie Water Division, Department of Engineering, Kashmar Branch, Islamic Azad University, 96716-97718 Kashmar, Iran Correspondence should be addressed to Ahmad Hosseini-Bandegharaei; Received 19 May 2013; Revised 14 September 2013; Accepted 19 September 2013 Academic Editor: Daryoush Afzali Copyright © 2013 Ahmad Hosseini-Bandegharaei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A stable extractant-impregnated resin (EIR) containing Chrome Azurol B was prepared using Amberlite XAD-2010 as a porous polymeric support. The new EIR was employed for trace separation and preconcentration of U(VI) ion followed by spectrophotometric determination with the arsenazo III procedure. CAB/XAD-2010 exhibited excellent selectivity for U(VI) ion over coexisting ions. Experimental parameters including pH, contact time, shaking speed, and ionic strength were investigated by batch extraction methods. Maximum sorption of U(VI) ions occurred at pH 4.3–6.9. The capacity of EIR was found to be 0.632 mmol⋅g−1 . Equilibrium was reached in 25 min and the loading half-time, t 1/2 , was less than 6 min. The equilibrium adsorption isotherm of U(VI) was fitted with the Langmuir adsorption model. In addition, a column packed with CAB/XAD-2010 was used for column-mode separation and preconcentration of U(VI) ion. For the optimization of the dynamic procedure, effects of sample volume, sample and eluent flow rate, eluent concentration, and its volume were investigated. The preconcentration factors for U(VI) were found out to be 160. But, for convenience, a preconcentration factor of 150 was utilized for the column-mode preconcentration. The dynamic procedure gave a detection limit of 5.0 × 10−10 mol⋅L−1 (0.12 𝜇g⋅L−1 ) for U(VI) ion. The proposed dynamic method showed good performance in analyzing environmental water samples. 1. Introduction Nowadays, a great attention is paid to the analytical monitoring of uranium in environmental samples due to its serious toxic effects even at low concentrations [1, 2]. Among the eminent techniques developed for the determination of uranium in environmental samples [3–7], preconcentrative separation of trace amounts of uranium from these samples followed by spectrophotometric determination, using arsenazo III procedure, has attracted much attention in the last decades [8–13]. This fact is due to availability, easy operation, and relative low operational and instrumental costs. Solid-phase extraction (SPE) has come to the forefront compared with other preconcentration techniques because of the development of solid adsorbents, including chelating polymeric supports, and the advantages in the use of these adsorbents in metal ions preconcentration. SPE offers several important advantages such as [12–18] the following: (i) higher enrichment factors, (ii) absence of emulsion, (iii) safety with respect to hazardous samples, (iv) minimal costs due to low consumption of reagents, (v) flexibility, (vi) ease of automation. In addition, several properties such as selectivity, simplicity of equipment, ease of operation, and the possibility of using adsorbents for many separation and preconcentration cycles without losses in the metal ion sorption capacity have made their use popular. 2 Extractant-impregnated resins, EIRs, have recently been developed for designing chelating polymeric supports and separating transition metal ions from aqueous media, because the preparation of chelating polymeric ion exchangers with chelating ligand connected to the polymer matrix by chemical bonds is usually very complex, time consuming, and costly. The preparation of chelating polymeric ion exchangers by the impregnation methods is exceedingly easy to perform, merely requiring stirring of an adequate extractant and the polymeric support. In addition, there is a wide choice of reagents for desired selectivity [19–26]. Therefore, by preparing a stable impregnated resin, one can combine the specific properties of an extractant, such as its selectivity, with the advantages of solid-ion-exchange technology for processing highly diluted solutions. Consequently, the extractantimpregnated resins (EIRs) are more suitable than conventional solvent extraction for recovering a specified metal ion with high selectivity. Among the studies concerning EIRs, several studies have been reported for polymeric supports in which an inert support is impregnated with a selective organic extractant to produce a solid sorbent used to separate and preconcentrate U(VI) from various analytical matrices [12, 13, 23–26]. In the followup of our group researches on the EIRs applications [12, 13, 27–31], this work focuses on the selective separation and preconcentration of trace amounts of uranium in various environmental water samples using a new EIR containing Amberlite XAD-2010 resin beads impregnated with Chrome Azurol B. Our new EIR sorbent showed excellent selectivity for U(VI) sorption from aqueous solutions. The adsorbed U(VI) ions stripped easily with 0.50 M HCl solution and the regenerated EIR could be used in subsequent cycles for U(VI) separation and preconcentration. In this paper, performance testing of the new EIR for solid-phase extraction of uranium is discussed. 2. Experimental 2.1. Reagents and Apparatus. Deionized water was used to prepare all solutions. Unless stated, all solvents and reagents used were analytical reagent grade and purchased from Merck (Darmstadt, Germany). Stock standard solution of U(VI) was prepared by dissolving the appropriate amounts of uranyl nitrate in deionized water, acidified with a small amount of HNO3 . The solutions of uranium(VI) were standardized gravimetrically (as U3 O8 ). Buffer solutions of pH 1–3, 4–6, and 7–9 were prepared by mixing appropriate ratios of 0.1 M HCl and KCl, 0.5 M acetic acid and ammonium acetate, and 0.5 M ammonia and NH4 Cl solutions, respectively. Chrome Azurol B (Chromazurol B; Mordant Blue 1; CI Mordant Blue 1; CI Mordant Blue 1, free acid; Eriochrome Blue SBB; Eriochrome Azurol B free form; Eriochrome Azurol 6B free form; EINECS 239-098-7), CAB (4-[(3Carboxy-5-methyl-4-oxo-1-cyclohexa-2,5-dienylidene)(2,6dichlorophenyl)methyl]-2-hydroxy-3-ethylbenzoic acid), and Amberlite XAD-2010 (surface area of 660 m2 g−1 , pore diameter 28.0 nm, and bead size 20–60 mesh) were obtained Journal of Chemistry from Sigma Chem. Co., St. Louis. The surface area, po (...truncated)