258 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Liquid-liquid Extraction of Palladium (II) in Acidic Chloride Solutions Using Tri-n-octylamine Hoda Pasdara*, Bahare Hedayati Saghavazb, Zhila Fallahc, Masoumeh Shahid, Mehran Davalloe a,b,c,d,eDepartment of Chemistry Islamic Azad University, North Tehran Branch, Tehran, Iran. aEmail: h_pasdar@iau-tnb.ac.ir Abstract The extraction of palladium in hydrochloric acid solution (200 ppm) using tri-n-octylamine (TOA) as extractant were performed in four different solvents (toluene, xylene, crosin and 1, 2-dichloroethane) via liquid-liquid method. The effect of extraction time and material concentration investigated for Pd (Ⅱ) extraction. The maximum extraction for palladium achieved with 1% TOA in 0.05 M HCl medium in 15 min with toluene. After the extraction, the Pd (Ⅱ)-loaded organic phase was stripped with different stripping agents. Results showed that Pd (Ⅱ) stripping is better achieved by 8 M ammonia solution. The percentage stripping of palladium (Ⅱ) was 100% in this condition. Keywords: Extraction; Palladium; Tri-n-octylamine (TOA); Liquid-Liquid; Stripping.Introduction. 1. Introduction Precious metals such as gold, platinum and palladium are important materials for the high technological industries such as decorative materials, dental materials, catalysts, fuel cells and electronic materials [1-5]. Due to the scarcity of these precious metals, the applications of processes for the extraction of platinum group metals (PGM) (ruthenium, rhodium, palladium, osmium, iridium and platinum) become essential [6]. In the attempt to recover the PGMs from the anthropogenic sources, many processes have been employed such as thermal process, leaching, liquid-liquid extraction, ion exchange, etc. [7-10]. This work deal with the liquid–liquid extraction technique. ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 259 Liquid-liquid extraction (LLE), also called solvent extraction (SX), is a process that allows the separation of two or more component due to their unequal solubilities in two immiscible liquid phases [11]. The high prices of precious metals like PGMs have been ensured that there is continued interest in the development of new extractants for the commercial concentration and separation of these metals. The extraction and separation of metals from source materials such as ores or spent catalysts or industrial waste need several multi-step procedures. The final refining stage is often based on hydrometallurgical treatments, which can be achieved by use of ion-exchange/LLE. [12]. Jaree and khunphakdee proposed a method for platinum and rhodium recovery in acidic chloride solution using tri-octylamine (TOA) in toluene. The percentage of extraction for Pt (II) and Rh was 97% and 21% respectively [13]. Shiro kiyyoyama reported the extraction of palladium with divinylbenzene microcapsules containing tri-n- octylamine as the extractant in an aqueous hydrochloric solution [14]. For liquid-liquid extraction, different chemicals have been used such as tributylphosphane (TBP), N, N'- dimethyl-N, N'-dicyclohexylthiodiglycolamide (DMDCHTDGA), 3-phenyl-4-acyl-5-isoxazolones and tri-iso- octylamine [15-17]. Amine derivatives are one of the main families of organic compounds that have been extensively considered for PGMs extraction particularly for Pd (II) and Pt (II) [18]. In our previous work, platinum was extracted by tri-n-octylamine in toluene from hydrochloric acid media [19]. In this paper the extraction of Pd (II) in acidic solution was carried out and TOA was used as extractant. Inductively Coupled Plasma (ICP) was applied to measure the amount of palladium. 2. Experimental 2.1 Materials All the reagents were analytical grade and used without further purification, unless otherwise mentioned. Stock solution of PdCl2 (200 ppm) were prepared by dissolving a weighted amount of palladium (II) chloride (Merck) in HCl (0.05 – 4 M). Toluene, xylene, crosin and 1, 2 dichloroethane were used as organic solvents. Tri-n- octylamine (TOA) used as extractant. Perkin Elmer Precisely-Optima 2100 DV Inductively Coupled Plasma (ICP) used for the determination of trace amount of palladium. Operating conditions for ICP are given in Table 1. Table 1: ICP operating conditions Plasma view axial Analysis time 0.5 s Plasma gas flow rate 150 L / min Sample flow rate 1.5 mL / min American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 260 2.2 Procedure For the palladium extraction, a required amount of TOA was added into 4 different solvents to form the organic phase. The organic phases and aqueous solution containing Pd (Ⅱ) (200 ppm) were added to a 50 ml beaker. Extraction and stripping experiments were generally carried out by stirring equal volumes of aqueous and organic phases (A/O=1) at room temperature and using a rotation speed between 900-1000 rpm. The agitation period for all the experiments considered between 5-15 min; afterwards, the organic phase and aqueous phase were separated by the use of a centrifuge at 2000 rpm for 5 min. The extraction efficiency (E %) of palladium ion are expressed as the following equation: 100% , ,, × − = palladiuminitial palladiumaqpalladiuminitial C CC E The symbols C initial, palladium and Caq, palladium represent the initial concentration of palladium ion and the instantaneous concentration in the aqueous phase, respectively. Stripping experiments were always performed for 15 min and different stripped agnates were used to remove the organic phase. 3. Results and discussion 3.1 Effect of contact time The contact time was varied from 5 to 15 min at room temperature. The effect of contact time on the extraction percentage (E %) is shown in Figure 1. In order to ensure the complete extraction, 15 min is chosen as the contact time in the following experiments. 3.2 Effect of tri-n-octylamin (TOA) concentration on palladium (II) extraction The extraction of palladium in different concentration of TOA in 4 different solvents (toluene, xylene, crosin and 1, 2 dichloroethane) over the 5-15 min of extraction time were carried out. Table 2 illustrates the effect of TOA concentration on palladium extraction. Figure 1 shows the difference between solvents and indicates that toluene is more effective. TOA contains a basic nitrogen atom, typically can react with a variety of inorganic and organic acids to form amine salts, which are capable of ion exchange with other anions. The following reaction, describe the protonation and ion exchange of TOA. Protonation: R3Norg + HXaq → R3NH+X- org , R= octyl, X= Cl Ion exchange: n MXn- m,aq. + n R3NH+X- org → (R3NH+)nMX- m,org + nX- aq. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 261 Table 2: Effect of TOA% on palladium extraction in different solvents. TOA% T ( min ) toluene % xylene % crosin % 1, 2 dichloroethane % 1 2.5 5 10 5 99.997 99.998 99.998 99.998 99.996 99.998 99.998 99.998 99.995 99.996 99.996 99.994 99.997 99.998 99.998 99.998 1 2.5 5 10 10 99.998 99.999 99.998 99.998 99.997 99.998 99.998 99.998 99.995 99.996 99.996 99.994 99.998 99.998 99.998 99.998 1 2.5 5 10 15 99.999 99.999 99.998 99.998 99.997 99.998 99.998 99.998 99.995 99.996 99.996 99.995 99.998 99.998 99.998 99.998 Figure 1: Effect of TOA% on palladium extraction in different solvents (a: toluene, b: xylene, c: crosin and d: 1, 2 dichloroethane). 3.3 Effect of hydrochloric acid concentration on palladium (II) extraction Equal volumes of aqueous solutions containing 200 ppm Pd (II) in 0.05 M to 8 M HCl, and organic phases with 1% TOA in toluene, were put in contact for 15 min. The extraction results obtained are displayed in Figure 2 99.994 99.995 99.996 99.997 99.998 99.999 100 1 2.5 5 10 t:5min t:10min t:15min 99.996 99.9965 99.997 99.9975 99.998 99.9985 99.999 99.9995 1 2.5 5 10 t:5min t:10min t:15min 99.9964 99.9966 99.9968 99.997 99.9972 99.9974 99.9976 99.9978 99.998 99.9982 1 2.5 5 10 t:5min t:10min t:15min 99.993 99.9935 99.994 99.9945 99.995 99.9955 99.996 99.9965 1 2.5 5 10 t:5min t:10min t:15min Extraction % Extraction % Extraction % Extraction % TOA% TOA% TOA% TOA% b a c d American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 262 which shows the dependence of Pd (II) extraction on HCl concentration. The extraction of palladium was 97.8% in 0.05 M HCl concentration. Figure 2: Variation of the palladium (Ⅱ) extraction with the HCl concentration (200 ppm Pd (Ⅱ) in 0.05-8 M; 2.5% TOA in toluen; A: O (v/v) = 1; room temperature; 10 min). 3.4 Palladium (II) stripping After the extraction, the Pd (II)-loaded organic phase was stripped with different stripping agents (A/O=1:10 and 15 min contact). Several stripping agents have been tasted to release Pd (II) from TOA: HClO4, H2SO4 and NH3 solutions up to 1M, 3M, 5M and 8M. The overall data achieved are summarized in Table 3. Table 3 shows that 8 M ammonia solution is a quite efficient stripping medium for Pd (II) removal from the TOA organic phase. In Figures 3-5 effect of concentration of stripped agents are shown. Table 3: Effect of different stripped agents % Extraction Stripping agents 1.85 96 99 100 1 M NH3 3 M NH3 5 M NH3 8 M NH3 0.02 0.02 0.02 0.02 1 M HClO4 3 M HclO4 5 M HclO4 8 M HclO4 0.02 0.075 0.02 0.02 1 M H2SO4 3 M H2SO4 5 M H2SO4 8 M H2SO4 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 263 Figure 2: The effect of HClO4 concentration on stripping Figure 3: The effect of H2SO4 concentration on stripping Figure 4: The effect of NH3 concentration on stripping 5. Conclusion The following conclusions are drawn from the present liquid–liquid extraction of palladium (II) process: 0 0.005 0.01 0.015 0.02 0.025 0 1 2 3 4 5 6 7 8 9 St rip pi ng % HClO4[M] 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0 1 2 3 4 5 6 7 8 9 St rip pi ng % [H2SO4 [M] 0 20 40 60 80 100 120 0 1 2 3 4 5 6 7 8 9 St rip pi ng % NH3 [M] American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 38, No 1, pp 258-264 264 1. Effect of time concluded that 10 min for palladium extraction. 2. The highest extraction of palladium achieved from TOA 1% in toluene with an A/O phase ratio equal to 1 (v/v). 3. Experiments show that 8 M ammonia solution is a quite efficient stripping medium for Pd (II) extraction. 4. This technique can be applied for continuous processes, like spent material or other related solutions. References [1] Trochimczuk, A.W.; Kabay, N.; Arda, M. & Streat, M. (2004). Reactive & Functional Plymers, 59, 1- 7. 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