Hindawi Publishing Corporation Journal of Chemistry Volume 2013, Article ID 482793, 7 pages http://dx.doi.org/10.1155/2013/482793 Research Article Tris(2-Aminoethyl)Amine-Functionalized Fe3O4 Magnetic Nanoparticles as a Selective Sorbent for Separation of Silver and Gold Ions in Different pHs Hamid �eza �ot� �adeh �had� Forouzan Aboufazeli� Omid Sadeghi� �ahid Amani� �zzatollah Na�a�� and Na�meh Tavassoli Department of Chemistry, Islamic Azad University Shahr-e-Rey Branch, P.O. Box 18735-334, Tehran, Iran Correspondence should be addressed to Najmeh Tavassoli; [email protected] Received 10 June 2012; Revised 15 July 2012; Accepted 16 July 2012 Academic Editor: Daryoush Afzali Copyright � 2013 Hamid Reza Lot� �adeh �had et al. is 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. e usage of tris(2-aminoethyl)amine-functionalized Fe O nanoparticles as a novel magnetic sorbent for rapid extraction, preconcentration, and determination of trace amounts of silver and gold ions was investigated. e optimum conditions for sample pH, eluent parameters (type, concentration and volume)3 4 were obtained. e effect of various cationic interferences on the adsorption of silver and gold was evaluated. e analytical efficiency values of both silver and gold ions were higher than 98.0 in the optimum conditions. e limits of detection (LOD) were less than 0.8 and 0.5 ng mL for silver and gold, respectively. e linear ranges for silver and gold were 1.5–1000 ng mL and 1.0–1000 ng mL respectively. e−1 maximum capacity of the modi�ed% magnetic nanoparticles was more than 97.3 mg g and−1 167 mg g for silver,−1 and gold ions, respectively. e presented method was used to determine silver and gold ions in real samples.−1 Finally, the−1 method accuracy was con�rmed by standard reference materials. 1. Introduction silver or gold ions in real samples such as electrothermal atomic absorption spectrometry (ETAAS) [4, 5], inductively Silver and gold have been known as precious metals for coupled plasma optical emission spectroscopy (ICP-OES) a long time. ey are used to make jewelry, high-value [6], inductively coupled plasma mass spectroscopy (ICP-MS) tableware, utensils, and so forth. e silver compounds are [7], and �ame atomic absorption spectroscopy (FAAS) [8]. extensively used in the processing of food, drugs, bever- Nowadays, electrothermal atomic absorption spectrometry ages, �lters, and other equipments of water puri�cation. (ETAAS) is one of the most powerful and common analytical ese compounds also play an important role in electrical techniques for determination of low concentrations of heavy applications, photographic �lm production, and fungicides metals due to being costless and easy operation [9]. But there manufacturing [1, 2]. On the other hand, high levels of are many difficulties in determination of heavy metals in silver are toxic to human cells, which can decrease the rate environmental samples by electrothermal atomic absorption of wound healing. Another problem caused by permanent spectrometry such as matrix interferences. However, this exposure to silver compounds is argyria, which cause a problem can be solved by preconcentration techniques due to permanent blue-gray discoloration of the skin [3]. Gold has the possibility of removing the sample matrix. Several meth- been high demanded for using in coinage, jewelry, and so ods have been developed and used for preconcentration and forth, since the beginning of the human history. For these separation of elements in trace concentrations according to reasons, extraction and determination of low levels of silver the nature of the samples, the concentrations of the analytes, and gold are important. ere have been lots of efforts and the measurement techniques. Some examples are ion for determining of these elements by researchers all over exchange [10], coprecipitation [11], solvent extraction [12], the world. Several techniques have been used to determine and adsorption [13]. Among all these techniques, adsorption 2 Journal of Chemistry is the most preferred technique because it is simple and does not consume high volumes of toxic solvents. Among variety of solid phases used for extraction of silver and gold such as activated carbon [14], pentathia-15-crown-5 [15], calix [4], arene [16], magnetic nanoparticles [17], modi�ed silica [18], and polymer gels [19], magnetic nanoparticles have gained much importance due to their high surface areas, chemical and mechanical stability, simplicity of synthesis, and on the top possibility of easy separation. ese magnetic nanoparticles could be easily functionalized with desired molecules using silane agents [20]. e silane group will be reacted with active hydroxyl groups on the surface of particles and cause formation of functionalized magnetic nanoparticles. F 1: SEM micrograph of TREN-functionalized Fe O nano- In this work, for the �rst time, the application of tris(2- particles. 3 4 aminoethyl)amine-functionalized Fe O nanoparticles as a magnetic solid phase for separation and determination of silver and gold from aqueous solutions3 4 was investigated. IR spectroscopy con�rmed the functionalization with fol- e effects of type, concentration, and volume of eluent, sample pH, and interfering ions on method efficiency were lowing results (KBr, cm ): 3445 (NH), 2913 (CH, aliphatic), studied. is method was applied to a numbers of industrial 1068 and 584 (Fe O ).−1 Elemental analysis of TREN-Fe O sample gave a tris(2-aminoethyl)amine concentration of and natural samples. Moreover, the method accuracy was 3 4 3 4 investigated by determination of gold and silver ions in 0.92 mmol g (C: 9.96, H: 2.13, N: 5.14 ). As the Fe O different standard reference materials. nanoparticles−1 and Si atoms would not decompose in elemen- tal analysis, so the burning part is this formula:% C H 3N 4. Considering the results, the TREN loading is calculated to be 2. Experimental 0.92 mmol g . e thermal stability of this sorbent has9 24 been4 investigated−1 by TGA/DTA analysis. e results show that this 2.1. Reagents and Materials. All materials were of analytical sorbent is stable up to 300 C (Figure 3). grade and used without any further puri�cation. Standard silver and gold ion solutions were prepared daily from ∘ stock solution of silver or gold solutions (1000 g L ) which 2.2. Apparatus. A Shimadzu (Kyoto, Japan) Model AA- 670G atomic absorption spectrometer equipped with a GFA- were purchased from Merck Company (Darmstadt,−1 Ger- 4A graphite furnace atomizer, an ASC-60G autosampler many). All reagents and solvents including sodium hydrox- ide, nitric acid, hydrochloric acid, thiourea, 3-chloropropyl and a circulating cooling unit were employed. To correct triethoxysilane, tris(2-aminoethyl)amine, and triethylamine the nonspeci�c absorbance, deuterium lamp background were purchased from Merck Company. All of the required correction was used. e operating conditions of hollow solutions were prepared using deionized water, provided cathode lamps and graphite furnace temperature programs from a Milli-� (Millipore, Bedford, Mass, �SA) puri�cation for gold and silver are mentioned in Table 1. Pyrolytically coated graphite tubes were used. Argon 99.999 (Roham system. Fe O nanoparticles with 305 m /g surface area gas Co., Tehran, Iran), with a �ow rate of 1.5 L min , was were synthesized according to the previous2 report [21]. Tris(2-aminoethyl)amine-functionalized3 4 magnetic nanopar- applied as a protective and purge gas. e measurements% −1 ticles were prepared by reacting of activated Fe O with silane were performed in the peak height mode which was preferred agents. over peak areas. A PreeKem WX-3000 microwave digestion system has been used for sample digestion. e speci�c For this approach, the surface of Fe O 3 was4 activated surface area was measured using a Micrometritics ASAP 2010 in a solution of 1 mol L of NaOH and then they were 3 4 analyzer. e thermal analysis was performed using a BAHR- suspended in 50 mL of−1 toluene. Aerwards 1.0 g of 3- ermoanalyse GmbH (Germany) employing heating at rates chloropropyltriethoxysilane was added to the mixture and of 10 C min in air atmosphere. was re�uxed for 24 hours. e solid phase was separated by a magnet and was suspended again in 50 mL of triethy- ∘ −1 lamine and toluene mixture (1 : 1 v/v), then 5 mL of tris(2- 2.3. Procedure aminoethyl)amine was added and re�uxed for 24 hours. ese particles were washed with 10 mL ethanol and dried at room 2.3.1. Preconcentration Method. In two separated 250 mL- temperature. Functionalization by tris(2-aminoethyl)amine stoppered-glass bottle, 100 mL of solutions containing was con�rmed by SEM photograph (Figure 1), IR spec- 1 g mL of Au(III) or Ag(I) ions were prepared. e troscopy, and elemental analysis. e average size of these pHs were−1 adjusted to 2 and 8 for Au(III) and Ag(I) nanoparticles calculated to be around 50 nm according to ions, respectively. en, 0.01 g of sorbent was added to SEM photograph (Figure 1). A schematic model for synthesis each solution and the mixtures were shaken for 5 min. of TREN-Fe O is shown in Figure 2. Subsequently, TREN-Fe O NPs were isolated by placing 3 4 3 4 Journal of Chemistry 3 EtO OH O OH + EtO SiCH2CH2CH2Cl O SiCH2CH2CH2Cl OH O EtO Fe3O4 nanoparticles O O CH2CH2NH2 N O SiCH2CH2CH2Cl + (NH2CH2CH2)3 O SiCH2CH2CH2 NHCH2CH2N O O CH2CH2NH2 O CH2CH2NH2 O CH2CH2NH2 ६ ६ O SiCH2CH2CH2 NHCH2CH2N + . O SiCH2CH2CH2 NHCH2CH2N . O CH2CH2NH2 O CH2CH2NH2 F 2: A schematic model for synthesis of TREN-functionalized Fe O nano-particles.