Kullanılmış Ve Kullanılmamış Floresan Lambalarda Cıva Tayini

thumbnail.default.placeholder
Tarih
2012-06-29
Yazarlar
Kırlangıç, Seçil
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Özet
Konutlarda, ticari ve sosyal alanda tüketilen elektrik enerjisinin büyük bir kısmı aydınlatma amacıyla kullanılır. Cıva içeren floresan lambalar ve cıva içermeyen lambalar (akkor lambalar) olmak üzere iki çeşit lamba vardır. Floresan lambalar akkor lambalar ile kıyaslanırsa; Verimliliği 3-6 kat daha fazladır. Lamba Ömrü 4-15 kat daha fazladır ve enerji tüketimi 80 daha azdır. Bir floresan lamba temel olarak içi fosfor tozları ile kaplanmış cam bir tüpten oluşur. Fosfor tozları % 1-2 antimon ve mangan içeren kalsiyum halofosfat “[Ca5(F,Cl)(PO4)3:Sb, Mn] karışımından oluşur. Bu küçük bileşenlerin miktarı değişebilir, bu da lambanın rengini etkiler. Cam tüp; düşük basınçta (0,003 atm) argon, neon, kripton veya ksenon gibi inert bir gazla ve düşük basınçta cıva buharı ile doldurulur. Tungsten veya paslanmaz çelikten yapılan katot, lambaların ucunda bulunur. Floresan lambanın içindeki cıva buharı tek başına görünür bölgede ışık üretemediği için; cıva fosfor tozlara çarparak görünür bölgede ışıma yapmayı sağlar. Bu tozun türü; lambanın verimini, rengini, renksel geri verimini etkiler. Tozun saflığı ve kristal boyutu da oldukça önemlidir. Floresan lambalar içinde bulunan yüksek miktarda cıva yüzünden önemli derecede çevresel sorunlara sebep olmaktadır. Çünkü; cıva toksik bir metaldir. Cıva doldurulmuş lambalar kırıldığında; cıva; suya, toprağa, bitkilere ve hayvanlara bulaşır. Senelerce floresan lambaların kullanımından doğan bu sorundan dolayı lambaları uygun bir şekilde bertaraf etme yolları aranmaktadır ve kısıtlama getirilmiştir. Avrupa Topluluğu’nun floresan lambalarda cıva miktarı için koyduğu limit lamba başına 5 mg’dır. Bu çalışmada; çeşitli markaların kullanılmış ve kullanılmamış floresan lambalarında cıva miktarının kriterlere uyup uymadığına bakılmıştır. Kriterlere uygun olduğu saptanmıştır. Kullanılmış ve kullanılmamış floresan lambalarda hidrür oluşturmalı atomik absorpsiyon spektrofotometresi ile cıva tayini yapılmıştır. Bu sistem ile cıva gibi ağır metallerin eser miktarda analizi yapılabilmektir. Hidrür oluşturma tekniğinin iki önemli avantajı vardır; Tayin elementi numune ortamından ayrılır. Bu da olası girişimleri azaltır. Gözlenebilme sınırı, μg/L veya daha düşük düzeylere getirilmiştir. Çünkü 1-50 mL numunedeki tayin elementinin tamamı birkaç saniyede atomlaştırıcıya gaz olarak gönderilir.
It is well known that mercury is one of the most toxic heavy metals in the environment. Different forms of mercury can be accumulatedin animals and plants. Mercury can damage central nevre by entering into human body. Mercury is a global pollutant which requires a great attention due to its bioaccumulation properties and reactivity. It is highly toxic even in low concentrations and its dispersion in the environment is due to natural emissions or anthropogenic activities. The main indirect source of human contamination of Hg is through the consumption of fish products (fish, crustaceans). The presence of Hg in fish, thermometers, dental amalgams, vaccine preservatives, electrical substances and in the atmosphere has made this particular toxic metal an increasing focus of health authorities and interest groups. Several mercury diseases have occured up to now. The most important disease is Minamata Disease. The National Institute for Minamata Disease was established in 1978 to carry out medical studies on Minamata Disease. The institute s Department of Clinical Medicine engages in clinical research to study Minamata Disease and treatments, carrying out medical examinations as necessary. The purpose of this research is to find the determinant properties of mercury compounds in given organisms, the flux of the compounds in organisms leading subsequently to their movement in the environment and chemical repercussions in an organic mechanism (in particular, the characteristics of damage caused by organic mercury and potential detoxification mechanisms). The Department of Epidemiology investigates and researches into Minamata Disease from an epidemiological perspective. The work done at the institute since its establishment is highly regarded by the scientific world and in 1986, the institute was designated as a WHO Collaborating Centre. A large part of the electrical energy consumed in public, commercial, residential, and service sectors is utilized in lighting. There are two main types of lamps – those that contain mercury (fluorescent lamps with mercury vapor, mercury–sodium vapor, and with other mixed metallic vapors) and those without mercury (incandescent lamps and halogen/dichroiclamps). Compared to incandescent lamps, the luminous efficiency of mercury-containing lamps is three to six fold as high, life time is from 4 to 15 times as long, and energy consumption is 80 % smaller. A fluorescent lamp is basically constituted of a glass tube internally coated with phosphorescent powders composed of “calciumhalophosphate with 1–2 % antimony and manganese “[Ca5(F,Cl)(PO4)3:Sb, Mn]”. The quantity of the seminor components may change slightly, depending on the color of the lamp. An alumina pre-coating may be found between the glass tube and the luminescent powder. The tube is filled with an inert gas (argon, neon, krypton, and/or xenon) at low pressure (0.003 atm) and mercury vapor at low partial pressure. Cathodes made of either tungsten or stainless steel are assembled on theends of thelamps. The tube is under partial vacuum. Fluorescent lamps rely on mercury as the source of ultraviolet radiation for the production of visible light. Fluorescent lamps raise important environmental concerns because of their high content of mercury. When the lamps are discarded, mercury may contaminate soil, plants, animals, and water. Fluorescent lamps’s extensive use over the years has caused growing concerns over their proper disposal. Therefore; the limit allowed by the European Community that is 5 mg per compact fluorescent lamp. Antimony, arsenic, bismuth, germanium, selenium, tellerium and tin, are forming gaseous hydrides in acid solution upon the additon of NaBH4. These hydrides can be purged from solution using an inert gas (usually argon) and transported to a heated quartz tube, where they are atomized. The tube may be heated electrically or by a flame. The advantage of the electrical heating is the lower running cost and the better temperature control. The relatively simple hydride generation technique makes possible detection limits that are comparable to or better than those of GF AAS. The atomization of hydrides at temperatures of 800 0C-1000 0C is a complex procedure that involves hydrogen radicals, which will not be discussed in detail here. Spectral interferences are very unlikely with this technique as only a few elements are volatilized under the conditions used here. Gas phase interferences are unlikely as well, except when other hydride-forming elements are present in the sample at high concentration. The only interference that can cause major problems is the hindrance of hydride generation and liberation from solution caused by some transition metals. Among the analytical techniques used for the determination of Hg, cold vapor atomic absorption spectrometry (CV-AAS) is widely applied since it is a low cost technique. Mercury is reduced to the metal under the conditions used for hydride generation and can be purged directly with an inert gas from solution as atomic vapor and measured in an unhealted absorption cell by AAS. This technique results in the best detection limits for mercury. There are two system at this tecnique: Batch and Flow system. The great advantage of flow systems is the easy automation. The addition of the solution for measurement, the transport of reagents and the separation of the gaseous hydride can all be managed automatically. It is characteristic for flow systems that sensitivity increases with decreasing flow rate. In this study; spent and new fluorescent lamp different marks was characterized to determine the distribution of mercury. It was determined optimum conditions such as shaking time, variety of solubility (microwave or normal beater). Concentrations of mercury is not over the limit per lamp. Mercury was determined from the phosphor powders that kind of them affects efficiency of lamp. As a technique; hydride generation atomic absorption spectrometry was used. Advantages of this technique;  Limit of detection is lowered degree of ppb (μg/L).  The special advantage of the hydride generation technique is its very high sensitivity combined with an effiecent separation of the analyte from the matrix. In addition this technique offers the possibility of a separate determination of the various oxidation states of the analytes. In this study high-resolution continuum source atomic absorption spectrometer (HR-CS AAS) was used as a machine. Components of HR-CS AAS are the radiation source, the atomizer, the optical system and the detector. In HR-CS AAS one single radition source is used for all elements and wavelengths, a xenon short-arc lamp. However, these commercially lamps don’t have enough energy in the far UV range, where most of analytical lines of AAS are located. It was therefore necessary to re-design this lamp type for ues in AAS. The emission intensity of this lamp is at least a factor of 10 higher than that of conventional xenon short-arc lamps and more tan a factor of 100 higher in the far UV range. The emmission intensity of this lamp is in average a factor of 100 higher than that of conventional HCL over the entire spectral range. One of the big advantages of HR-CS AAS is for sure that only a single radition source is required for all elements and all wavelengths over the entire spectral range from (190-900 nm). Another advantage results from the significantly higher emission intensity of this lamp. Although the radiation intensity has no influence on sensitivity in AAS, it has an influence on the signal-to-noise ratio. As a result of this, detection limits are in average about a factor of 5 better in HR-CS AAS, compared to line source AAS. In HR-CS AAS the same atomizers are used as in classical line source AAS. The optical system in HR-CS AAS is fundamentally different from that in AAS, although similar components are used. The use of a continuum radiation source requires a high resolution monochromator. Classical monochromators of this type, as they were used in optical emmision reqiure a lot of space and have a tendency to exhibit wavelength drift. Both of these characteristics are unacceptable.in HR-CS AAS. This problem was solved with the design of a compact double monochromator with active wavelength stabilization. In HR-CS AAS a linear CCD array with typically 512 pixels is used as the detector, 200 of which are used for analytical purposes. All the 200 pixels are illuminated and read out simultaneously. As only three pixels are used in most cases to measure atomic absorption, the others may be used for correction purposes. This results in an extremely stable system with low noise level and significantly improved signal-to-noise ratios.
Açıklama
Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2012
Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2012
Anahtar kelimeler
cıva, floresan lamba, hidrür sistemi, soğuk buhar atomik absorpsiyon spektrometresi, mercury, fluorescent lamp, hydride system, cold vapor atomic absorption spectrometry
Alıntı