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Nadir toprak elementleri minerallerinden bazı lantanitlerin kazanılması ve seryumun floresans spektroskopisi ile belirlenmesinde yeni bir yöntem

The Recovery of some lanthanides from rare earth minerals and a new method for the determination of cerium by fluorescende spectrometry

  1. Tez No: 21702
  2. Yazar: YENER RAKICIOĞLU
  3. Danışmanlar: DOÇ. DR. AYÇİÇEK AKSELİ
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya, Chemistry
  6. Anahtar Kelimeler: Elektron mikroskobu, Lantanitler, Nadir toprak elementleri, Seryum, Electron microscope, Lanthanids, Rare earth elements, Cerium
  7. Yıl: 1992
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: Belirtilmemiş.

Özet

fraction groups, this elution can be adopted to some other minerals those include rare earth elements in different percentages. The eluent used is known as an expensive material. The amount of eluent used in this work has been decreased as compared to the that used in the literature. At the same time the volume of the eluent can be decreased when the pH of eluent is increased after obtaining cerium fractions. In this case La fractions mill come earlier and this will further lessen the amount of the eluent used. It has been found that the elution period and the volume of the eluent is decreased. In this study the determination of the concentration of elements obtained in fractions after elution was performed by the spectrophotometry method using Arsenazo I reagent. Then the fraction groups of every element were collected and precipitated with oxalic acid. The precipitate of each element was ignited to their oxides and the colour of these oxides were used identification of the elements (La: white, Ce: yellow, Pr: dark brown, Nd: light blue). At the second part of this study, we investigated the fluorescence properties of cerium hexatnetaphosphate ' complex. It is well known that the analytical problems encountered in the determination of lanthanide ions, especially as traces in solutions, arise from their very similar chemical properties. Therefore, it is extremely difficult to find specific reactions for the individual ions. Spectrophotometry methods produce satisfactory resullts for only high lanthanide concentrations, since the molar absorptivities of the individual ions are rather low. Better results are obtained using optical emission spectra or activation analyses, but it is still difficult to determine traces of individual lanthanides in complex mixtures. Fluorometry has been partially successful because the fluorescence intensity of solutions of common soluble salts of the lanthanides are fairly low. Sodium hexaasetaphacphate acts as a specific reagent for enhancing the fluorescence intensity of cerium in aqueous solutions. -IX-

Özet (Çeviri)

THE fHUUER/ DF SCFE LflNTHfMKB FRCM RARE EARTH MİNERALS AND A NELJ MEIHD FOR THE DEJER*röTİDN CF GERİLİM BY FLUDFESCEME SRIflRJMETRY SUMHARY The rare earth group of elemen-is, also called the lan- thanides is composed of fifteen elements uıith atomic numbers betusen 57 and 71. Yttrium atomic number 39 is found naturally uıith the rare earths. The lanthanides may be generally classified as the light (atomic number 57 to 60) ör heavy (atomic number 64 to 71) rare earths including yttrium. These terms are derived from the fact that the“light”materials are generally more soluble than the“heavy”ones in a given solvent system. it is difficult to obtain the rare earth elements from their tninerals as uell as to separate them from each other because of their similar chemical properties. in addition, the detection of those elements are rather difficult due to again the same reason mentioned above. Before the development of the ion exchange methods in 1941 to 1947, fractional crystallization, fractional precipitation and fractional thermal decomposition had been used in order tD get över these problems. But unfortunately» these classic methods are laborious and time consuming. Nouadays, the most effective tool, for the separation and purification of rare earths is the ion exchange method, utilizing synthetic ion-exchange resins. Separation the rare earths using a suitable eluting agent is an important step. The effectiveness of separation for an experimental arrangement depends on such parameters as temperature, type and size of the cation exchange resin particles, dimensions of the column, conc^fitration, pH and flou rate of eluting agent. -vi-in this study strong acid type cation exchange resin Douex 5Dül-X8, 2DD-4DD mesh and elution solution of^ hydroxyisobutyric acid (c*HIB) uere used. Commparison af the relative separation factors uith other eluents indicates that this eluent is so far the best. At first an artificially prepared mixture of rare earth elements has been studied. The uashed resin, after being kept in uater overnight, uıas transfsrred to the column, the resin uas then equilibrated uith İM e<HIB. Then an elution solution with pH 3.5 uas placed in the first flask. The other elution snlution mith lou pH 3.0 uas placed in the second flask uhich uas equipped uith a magnetic stirrer. The rate of elution uas adjusted uith a pump, placed after the flasks.ı The colutnn uas 40cm long by 1.2cm internal diameter uith porcelain strainer on the bottom. t/HIB solutions, (uith pH 3.0 and pH 3.5) uere used as the eluent, respectively and flou rate of 60ml/hour uas chosen. Under these conditions, elution time and eluent volume are better than those found in the literatüre. Afteruards by considering these results,ue uere tried to separate some rare earth elements from a mixture of rare earth oxides obtained from a French monazite. For the separation of rare earth groups, the follouing procedure uas applied: 1-The ground sample uas dissolved uith perchloric acid, 2-Thorium and rare earth elements uere precipitated uith ammonium oxalate, 3-The precipitate uas dissolved uith HNO, -HC10 j 4 mixture, 4-Step 2 uas repeated, 5-Step 3 uas repeated, 6-The solution uas boiled, and pH uas adjusted to 2 uith ammonia and HNO,* Thorium uas precipitated as benzoate and after ignition it uas ueighed as ThD_ 7-The other rare earths uere precipitated from the filtrate as their benzoates in the presence of excess ammonia and after ignition ueighed as their oxides. -vii-The fluorescence measurement of cerium hexametaphosphate in aqueous solutions showed that the maximum fluorescence intensity is obtained by irradiating this lanthanide at 314nm in D.D5N sodium hexametaphosphate solution. In such solutions the calibration curve is linear for cerium concentrations belouj 16D j/g/ml. The effects of other rare earth on the fluorescence intensity of cerium hexametaphosphate mas investigated. It has been seen that there isn't any interferences from other rare earth elements. ; As a rssult, this new spectrof luorometric method can be used successfully for the qualitative and quantitative trace determination of cerium. ?x-fraction groups, this elution can be adopted to some other minerals those include rare earth elements in different percentages. The eluent used is known as an expensive material. The amount of eluent used in this work has been decreased as compared to the that used in the literature. At the same time the volume of the eluent can be decreased when the pH of eluent is increased after obtaining cerium fractions. In this case La fractions mill come earlier and this will further lessen the amount of the eluent used. It has been found that the elution period and the volume of the eluent is decreased. In this study the determination of the concentration of elements obtained in fractions after elution was performed by the spectrophotometry method using Arsenazo I reagent. Then the fraction groups of every element were collected and precipitated with oxalic acid. The precipitate of each element was ignited to their oxides and the colour of these oxides were used identification of the elements (La: white, Ce: yellow, Pr: dark brown, Nd: light blue). At the second part of this study, we investigated the fluorescence properties of cerium hexatnetaphosphate ' complex. It is well known that the analytical problems encountered in the determination of lanthanide ions, especially as traces in solutions, arise from their very similar chemical properties. Therefore, it is extremely difficult to find specific reactions for the individual ions. Spectrophotometry methods produce satisfactory resullts for only high lanthanide concentrations, since the molar absorptivities of the individual ions are rather low. Better results are obtained using optical emission spectra or activation analyses, but it is still difficult to determine traces of individual lanthanides in complex mixtures. Fluorometry has been partially successful because the fluorescence intensity of solutions of common soluble salts of the lanthanides are fairly low. Sodium hexaasetaphacphate acts as a specific reagent for enhancing the fluorescence intensity of cerium in aqueous solutions. -IX-The fluorescence measurement of cerium hexametaphosphate in aqueous solutions showed that the maximum fluorescence intensity is obtained by irradiating this lanthanide at 314nm in D.D5N sodium hexametaphosphate solution. In such solutions the calibration curve is linear for cerium concentrations belouj 16D j/g/ml. The effects of other rare earth on the fluorescence intensity of cerium hexametaphosphate mas investigated. It has been seen that there isn't any interferences from other rare earth elements. ; As a rssult, this new spectrof luorometric method can be used successfully for the qualitative and quantitative trace determination of cerium. ?x-

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