Bazı eser elementlerin adsorpsiyonla zenginleştirilmesi ve alevli AAS ile tayini
Determination of some trace elements in AAS after concentration by modified silicas
- Tez No: 18820
- Danışmanlar: DOÇ.DR. SÜLEYMAN AKMAN
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1991
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 46
Özet
ÖZET Bu çalışmada, amino ve tiol modifiye silikaların özellikleri ve hazırlanışları, zenginleştirme uygulamaları ve alevli atomik absorpsiyon spektrometresi (AAS) ile eser miktardaki Kadmiyum ve Bakır elementlerinin tayinleri anlatılmıştır. Modifiye silikalar hazırlanırken, ilk olarak silika derişik hidroklorik asitle 30 dakika muamele edildi, sonra, yıkama sularında klor iyonu kalmayıncaya kadar saf su ile yıkandı ve 150°C de bir gün kurutuldu. Kuru silika metanol içine kondu ve amino modifiye silika eldesi için (C2Hs0)3 Si(CH2)3NH2 ( 3-aminopropil trietoksisilan), tiol modifiye silika eldesi için de (CHaO) Si(CHa)3 SH( 3-merkaptopropil trimetoksislan) ilave edildi. Metanol vakum altında uzaklaştırıldıktan sonra kalan silika tekrar 150°C kurutuldu ve yıkama suları berraklaşıncaya kadar distile su ile yıkandı. Modifiye silikaların özellikleri, hazırlamada kullanılan silikaların özelliklerine bağlıdır. Bu çalışmada, 496 m2/gr yüzey alanlı silika kullanılmıştır. Bu yüzey alanı amino modifiye silikalarda 290 m2 / gr iken tiol modifiye silikalarda 410 gr/m2 dir. Bütün adsorbsiyon deneylerinde“Batch (çalkalama)”ve“Kolon”yöntemleri kullanılmıştır. Kadmiyum ve bakır elementlerinin adsorbsiyonunda, pH'ın çalkalama süresinin ve tampon çözeltisinin cinsinin etkileri incelenmiştir. vı
Özet (Çeviri)
SUMMARY DETERMINATION OF SOME TRACE ELEMENTS IN AAS AFTER CONCENTRATION BY MODIFIED SILICAS. In this work, the preparation and characteristics of amino-and thiol-modif ied silicas and their applications to the preconcentration and determination of trace amounts of copper and cadmium by flame atomic absorption spectrometry are described. Normally metal ions can be deposited by ionexchange or adsorbtion on metaloxid surfaces. This procedure can be modified and sometime be more selective by changing the surface properties of the oxide. This has frequently been done by physical methods like treatment at higher temperatures. The last 20 years chemical reactions have been widely employed. Being covered with hydroxyl groups (silanol groups), the surface of silica can be modified in many ways and a large number of different groups can be attached to its surface. Silica gel can be considered to be an amorphous condensation polymer of silicic acid. Conventionally, it is made by mixing aqueous solution of sodium silicate and trisilicic acid are formed and condense with one another. Silicic acid first condenses with itself to form disilicic acid and water, the Vlldisilicic acid condenses with silicic acid to form trisilicic acid and so on. Condensation between two molecules of disilicic acid is also possible. This stage leads to a collodial solution o f spheroidal particles of polysilicic acids which have a diameter of about 10 nm (10 nm = 100 A ) and contain roughly ten thousands silicon atoms each. The collodial solution eventually forms a hidrogel that is washed and dried to produce silica gel. Further condensation, inter and intraparticle, occurs during these stages. During drying, the surface tension forces of water collapse the original, very open, texture until the mechanical strength of the agglomeration of particles becomes sufficient to resist further collapse. The remaining water then evoparates leaving a material of large area and substantial pore volume whose texture must rather resemble that of a loosely packed gravel bed. Silica gels of differing textures can be prepared by variations in the techniques of preparation and by aging of the gel subsequent to its formation. Most commercial silica gels are either of the narrow pore type (average pore diameter about 2.5 nm, specific area about 700 m* per g, and pore volume about 0.4 cc per g) or of the wide pore type (average pore diameter about 14 nm, spesific area about 300 mz-per g, and pore volume about 1.1 cc per g). Our work has employed mostly the narrow pore silica gel. The following silylation reaction offers attractive posibilities for the attachment of a variety of organic residues to silica gel. viiia - OH CH O OCH 3 \ / 3 cr - OH CHoO X : Any amino group, eg.-NHz or -NHCH2CH2CHZNH2 If either the -NH or -NHCH CH CH NH gel 2 2 2 2 2 is treated with a solution of metals, substantial quantities of ions are taken up by the gel via coordination to the amino groups. In many respects, the chemistry of thiols is like that of alcohols. Thus thiols can be readily prepared by the reaction of sodiumhdyrosulf ide (NaSH) with those alcly holides, sulfates or sulfonate. C HcBr + NaSH C H SH + NaBr 2 -J 2 » Since thiols are acids of comparable strengdth to hydrogensulf ide (Ka = 6 x 10"^, more or less of the thioether may be produced by the following sequence of reactions unless the sodium hdyrosulfide is used in large excess. C2H5SH + NaSH C2H5SNa + H2S C2H5SNa + C2HBBr thiourea S-ethyl isothiouronium bromide C2HBSH + NH2CN as polymer Tertiary thiols can be synthesized by the addition of hydrogen sulfide to suitable alkenes with acid catalysts. This reaction is of course analogoues to the hydration of alcenes. CH3 H SO CH3 CH - C = CH, + H S - ?-> CH - C - CH 3 2 Z '3 3 Thiols do not form as strong intermolecular hydrogen bonds as do alcohols, and consequently the low-molecular -weight thiols have lower boiling points than alcohols. Thiols form insoluble balks with heavy metals, particularly mercury. This behavior is the origin of the common (but now disfavored) name, mercaptan for thiols. The purpose of this research is to study the interaction of metals and modified silica gels. It is especially interesting to investigate silica gels, modified with CH2CH2CH2SH and CH2CH2NH2 groups on the surface and their metal adsorbtion properties in water solutions of chlorids of metal ions. For the preparation of modified silicas, the silica was first digested with concentrated hydrocloric acid for 30 min., then washed with distilled water until no chloride appeared in the washings and dried at 150°C for one day. The silicas suspended in methanol were impregnated with (C2H50)3 Si (CH2 )3 NH2 (3-Aminopropyltriethoxysilane) and (CHjO^Si (CH2) ^H(3-Mercapt o propyltrimethoxy-silane) to obtain amino- and thiol- modified silicas, respectively and the methanol was evaporated under vacuum. The residual silica was dried 150°C and washed with distilled water until washings appeared clear. The characteristics of modified silicas are naturally dependent on the untreated silica. In this study, 30-70 mesh ASTM silica with a surface area 496 m2/g was used. The surface areas of amino- and thiol- modified silicas are 290 and 410 m2/g, respectively, whereas copper capacities of those are about 1.0 and 0.7 mg Cu/g silica, respectively. Both batch and column methods are used in experiments. In batch method, the effects of pH, shaking time and the kind of buffer on adsorption of copper and cadmium were investigated. Copper and cadmium were quantitatively adsorbed on both amino- and thiol- modified silicas at slightly acidic media. A shaking time of 30 min. was enough for a quantitative adsorbtion of the metals. Both copper and cadmium adsorbed on silicas were quantitatively recovered with 2 M hydrochloric acid. The elements studied were determined by flame atomic absorption spectrometry. XI
Benzer Tezler
- Deniz suyu ve mineral sulardaki bazı eser elementlerinin Al (OH)3 ile birlikte çöktürülerek ayrılması ve faas ile tayini
Separation of some trace elements in seawater and mineral water by coprecipitation with aluminum hydroxide and their determination by flame atomic absorption spectrometry
ASLI EGE
- Yüzey modifikasyonlu demir oksit manyetik nanopartiküller kullanılarak çevre örneklerinde bulunan eser elementlerin yüksek doğruluk ve duyarlılıkta tayinleri
High accuracy and sensitivity test of work elements in environmental samples using surface modificated iron oxide magnetic nanoparticules
BİRGÜL ÇELİK
- Bazı eser elementlerin XAD-2000 reçinesinde zenginleştirildikten sonra AAS ile analizleri
Analysis of some trace elements with AAS after enrichment on XAD-2000 resin
CELAL DURAN
- Pirinç kabuğu ve külü üzerinde bazı eser elementlerin adsopsiyonunun ve desorpsiyonunun incelenmesi
Adsorpsiyon and desorpsion of some trace elements on rice husk ash
DİLEK BAKIRCIOĞLU
- Bazı eser elementlerin deta (dietilentriamin) polimeri üzerinde zenginleştirilerek alevli atomik absorpsiyon spektrofotometresi ile tayini
Determination of some trace elements by flame atomic absorption spectrometryafter preconcentration using a deta (diethylene triamine) polymer
YASEMİN BAKIRCIOĞLU
Doktora
Türkçe
2000
KimyaTrakya ÜniversitesiKimya Ana Bilim Dalı
PROF. DR. SÜLEYMAN AKMAN
PROF. DR. HİLMİ İBAR