Extraction study of gadolinium (III) by di-n-butyldithiophosphate (DBDTP) ligand as complex agent

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1 IBN Extraction study of gadolinium (III) by di-n-butyldithiophosphate (DBDT) ligand as complex agent Roni Muhamad olihin*, Yayah Mulyasih, Anni Anggraeni Analytical Laboratory, Department of Chemistry, Faculty of Mathematics and Natural ciences, adjadjaran University, umedang, West Java, Indonesia * Abstract The researches for suitable process to recover high purity, and large amount of gadolinium have increased due to wide applications of gadolinium. In this research, gadolinium extraction will be studied through complex formation with di-n-butyldithiophosphate (DBDT) as ligand on various ph of 2,0; 3,0; 4,0; 5,0; 6,0; and 7,0 and various mole ratio of gadolinium to DBDT of 1:1; 1:2; and 1:3 then was extracted with petroleum ether to obtain of gadolinium extraction optimum condition. Concentration of gadolinium in aqueous phase was analyzed by Inductively Coupled lasma-mass pectroscopy (IC-M), whereas Gd-DBDT complex in organic phase was analyzed by spectrophotometer ultraviolet-visible (UV-Vis) and infrared (IR). The result shows that the highest value of gadolinium extraction percentage is reached at ph 5, 6, and 7 which are 99.64%, 99.74%, and 99.79% respectively when mole ratio of gadolinium to DBDT is 1:3, whereas gadolinium extraction percentage when mole ratio of gadolinium to DBDT is 1:1, 1:2, and 1:3 are 99.67%, 99.73%, and 99.79% respectively at ph 7. Di-n-butyldithiophosphate (DBDT) ligand gives maximum absorbance at λ nm, whereas Gd-DBDT complex in organic phase as extraction result give maximum absorbance at λ nm. Infrared spectrum of DBDT ligand shows absorption band at υ cm -1 from vibration of --NH 4 and absorption band at υ cm -1 from vibration of =, however these both absorption band weren t show at infrared spectrum of Gd- DBDT complex. These are shows that DBDT react with gadolinium which are predicted to formed Gd-DBDT and extracted to organic phase. Keywords: complex compound, di-n-butyldithiophosphate, gadolinium, petroleum ether, solvent extraction Introduction The wide applications of gadolinium, that one of the rare earth elements (REEs), have increased the search for suitable process to recover high purity, and large amount of the metal. Gadolinium yttrium garnets are used in microwave applications and gadolinium compounds are used in making phosphors for color TV tubes. About 1% of gadolinium in iron, chromium, and related alloys improves the workability and resistance to high temperatures and oxidation. The extreme low noise characteristics of gadolinium ethyl sulfate make it use in duplicating the performance of amplifiers, such as the maser. ince gadolinium is ferromagnetic, it can be used as a magnetic component that senses hot and cold. Numerous Gd(III) complexes are used as active constituents of pharmaceuticals employed as contrast agents in clinical MRI diagnostics. The revealing of extraction mechanism and separation possibility of gadolinium will contribute to the various advance materials manufacturing (Arai et al., 2007). Chemically the mineral monazite is an important source of REEs, especially the light lanthanides (Gupta and Krishnamurthy, 1992). The composition of monazite-bearing sands varies from one deposit to the other, so that a general flow sheet for monazite processing cannot be given. Monazite-bearing sands usually contain other rare earth (RE) minerals such as xenotime, gadolinite, thorite, uranothorite and samarkite (Mustafa, 2003). This mineralogical complexity highlights the importance of mineralogical studies for the efficient extraction of the mineral of interest (Hammoud, 1973). uch complex mixture requires intensive treatment to separate the marketable products (Rabie, 2007). Di-n-butyldithiophosphate (DBDT) is better on extraction of metal ions than dietyldithiophosphate. Therefore DBDT or its derivate with longer alkyl chain has many advantages when used as extractant on solvent extraction (Bahti, 1990). H 9 C 4 H 9 C 4 O O Figure 1 tructure of ammonium-dbdt 118

2 In this research, solvent extraction of Gd(III) through complex formation with DBDT will be studied. Materials and Methods Materials All reagent used were of analytical grade. Gadolinium solution was prepared from gadolinium oxide (Aldrich) which is diluted in nitric acid. 2 5 and n- butanol were used to prepare DBDT. Hydrochloric acid, potassium chloride, acetic acid and sodium acetate were used to prepare various buffer solutions. etroleum ether was used as organic solvent. Apparatus Digital ph-meter was used for the ph measurements, UV-Vis Ultrospec 3000 pro and spectrophotometer IR himadzu pectro-22 for spectrophotometric measurements, and IC-M was used for Gd(III) concentration analysis. Methods DBDT was prepared by reacting 2 5 and n-butanol at 80 C using reflux method, and stirred continuously until all 2 5 is dilute. olution ph is adjusted to 7 by ammonia adding, therefore evaporated until solvent removed. DBDT that formed was crystallized by methanol adding. Extraction of Gd(III) was carried out by mixing equal 10 ml of aqueous and organic phase in separatory funnel. olution was shaken for 10 minutes and stand for 10 minute until both phases are separated. Gd(III) concentration in aqueous phase were analyzed using IC-M. Results and Discussion Characterization of DBDT DBDT is not stored in market. In this study, it was synthesized as its ammonium salt. This compound is dissolved in methanol and water but solve in mixed of methanol and water (9:1). The UV spectrum of DBDT at nm is showed on Figure 4, whereas Figure 5 shows its IR spectrum. The UV spectrum show peaks at nm which is considered as π to π* transition absorption. The π to π* transition is appeared because there is double bond which is = in DBDT structure. The IR spectrum shows us several absorption bands. Absorption band at υ cm -1 is considered as N-H stretch from ammonium fungsional groups. Absorption band at υ cm -1 is for C-H aliphatic stretch from C 4 H 9. At fingerprint region, there are absorption band at υ 1066,64 cm -1 and 891,11 cm -1 with strong intensities that occurred from vibration of CH 2 -O--. The other absorption band is at υ cm -1 which is a specific vibration that comes from N-H fungsional group. Absorption band from = fungsional group is appear at υ cm -1 (ilverstein et al., 1991). Extraction of Gd(III) by DBDT In this research, Gd(III) on aqueous phase was expected react with DBDT to form Gd-DBDT complex which then was extracted to organic phase. Reaction between Gd(III) with DBDT was estimated like the equation showed bellow: Gd 3 3NH 4 -DBDT Gd(DBDT) 3 3NH 4 From the reaction above, we can see that reaction between Gd(III) with DBDT was influenced by solution ph because NH 4 was released as reaction product. Therefore Gd-DBDT complex stability was influenced by solution ph. In this research, optimum ph for Gd(III) extraction was studied. The effect of mole ratio of Gd(III) to DBDT also studied in this research. Figure 2 shows analysis result of Gd(III) extraction on various ph using IC-M. Extraction (%) Figure 2 Effect of ph to Gd(III) extraction percentage. According to the Figure 2, Gd(III) extraction percentage is increase due to increasing of solution ph. At lower ph, Gd(III) extraction percentage is smaller than at higher ph. This can be caused by formation of disulfide bond between DBDT molecules as a reaction product of acid oxidation to DBDT (Bahti, 1990). Figure 3 shows analysis result of gadolinium extraction on various mole ratio of Gd(III) to DBDT using IC-M. ph 119

3 Extraction (%) mole of DBDT (mole of Gd=1) Figure 3 Effect of mole of DBDT to Gd(III) extraction percentage. Figure 3 shows that almost of Gd(III) in aqueous phase is extracted to organic phase when mole ratio of Gd(III) to DBDT is 1:1, 1:2, and 1:3. According to Figure 3, there isn t any sign of influenced of mole DBDT when mole ratio of Gd(III) to DBDT are 1:1, 1:2, and 1:3. At these condition, extraction percentage of Gd(III) almost have same value. Therefore, advance research with more various mole ratios is needed to reveal influence of mole of DBDT to Gd(III) extraction percentage Abs nm DBDT Wavel ength ( nm) Figure 4 UV spectrum of NH 4 -DBDT. 105 %T DBDT /cm Figure 5 IR spectrum of NH 4 -DBDT. 120

4 Characterization of Gd-DBDT complex as extraction result in organic phase Organic phase as extraction result was analyzed by spectrophotometer UV-Vis. Figure 6 show UV spectrum of Gd-DBDT in organic phase as extraction result. If it compared to DBDT spectrum, there is chemical shift on Gd-DBDT spectrum. Maximum absorbance on Gd-DBDT spectrum is shifted to the longer wave length (lower energy) which is from nm to nm. This chemical shift is predicted come from occurrence of lengthening of conjugation system or delocalization of π electron which come from new compound. This phenomena give us a clue that there is reaction between Gd(III) and DBDT to form new compound which is predicted as Gd-DBDT complex compound. Organic phase also was analyzed by spectrophotometer IR. Figure 7 show Gd-DBDT (as extraction result) IR spectrum which was compared to DBDT IR spectrum. Abs Gd-DBDT nm Wavel ength ( nm) Figure 6 UV spectrum of Gd-DBDT = Gd-DBDT complex = DBDT ligand Figure 7 IR spectrum of Gd-DBDT compared to NH 4 -DBDT. 121

5 On the DBDT spectrum, there are absorption band at υ cm -1 which come from vibration of --NH 4 but this absorption band doesn t occurred on Gd-DBDT spectrum which predicted that bond between and NH 4 is broken, because form a new bond with Gd(III). There is also absorption band at υ cm -1 for vibration of = on DBDT spectrum, but this absorption band neither occur on Gd-DBDT spectrum which predicted that there is delocalization of π to atom, because atom form coordination covalent bond with Gd(III). This phenomena give us a clue that there is reaction between Gd(III) and DBDT to form new compound which is predicted as Gd-DBDT complex compound. Conclusions There is reaction between Gd(III) and DBDT to form new compound which is predicted as Gd- DBDT complex compound which is proved from the difference between UV and IR spectrum of DBDT and Gd-DBDT from organic phase as extraction result. Almost Gd(III) in aqueous phase can be extracted to organic phase at ph 5, 6, and 7 with gadolinium extraction percentage are 99.64%, 99.74%, and 99.79% when mole ratio of Gd(III) to DBDT is 1:3. Almost Gd(III) in aqueous phase also can be extracted to organic phase when mole ratio of Gd(III) to DBDT are 1:1, 1:2, and 1:3 at ph 7 with gadolinium extraction percentage are 99.67%, 99.73%, and 99.79%. There isn t any sign of influenced of mole DBDT when mole ratio of Gd(III) to DBDT are 1:1, 1:2, and 1:3. Therefore, advance research with more various mole ratios is needed to reveal influence of mole of DBDT to Gd(III) extraction percentage. Acknowledgements The authors are grateful to Geology Laboratories of Research and Development of Geology and Oceanic Centre Bandung for IC-M Analysis. References Arai,T., Y. Wei, M. Kumagai, & K. Horiguchi eparation of rare earths in nitric acid medium by a novel silica-based pyridinium anion exchange resin. Journal of Alloys and Compounds : Bahti, H.H Chromatography studies of metal dialkyldithiophosphates. University of New outh Wales, Australia. Thesis. Gupta, C.K. & N. Krishnamurthy Extractive metallurgy of rare earths. Int. Mater. Rev. 37 (5): Hammoud, N hysical and chemical properties of some Egyptian beach economic minerals in relation to their concentration problems. h.d. Thesis, Cairo University, Cairo, Egypt. Mustafa, M eparation of economic minerals and discovery of zinc, lead, and mercury minerals in the Egyptian black sands. The Third International Conference on The Geology of Africa, Assuit, Egypt, pp Rabie, K.A A group separation and purification of m, Eu and Gd from Egyptian beach monazite mineral using solvent extraction. Hydrometallurgy 85:81 86 ilverstein, R.M., G.C. Bassler, & T.C. Morril pectrofotometric identification of organic compound. Fifth Edition. John Wiley and ons, Inc. New York. 122

Available online Journal of Scientific and Engineering Research, 2016, 3(6): Research Article

Available online Journal of Scientific and Engineering Research, 2016, 3(6): Research Article Available online www.jsaer.com, 2016, 3(6):145152 Research Article ISSN: 23942630 CODEN(USA): JSERBR Preparation of High Purity Phosphatic Salts from Purified Phosphoric Acid Laila A Guirguis, Nagwa I