Sulardan kurşunun kil mineralleri kullanılarak adsorbsiyonu
Başlık çevirisi mevcut değil.
- Tez No: 75468
- Danışmanlar: DOÇ. DR. LÜTFİ AKÇA
- Tez Türü: Yüksek Lisans
- Konular: Çevre Mühendisliği, Environmental Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Çevre Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 122
Özet
Çevrede bulunan ağır metaller canlı sağlığını ciddi bir şekilde tehdit etmektedir. Farklı yollarla organizmaya giren ağır metallerin oldukça önemli miktarı biyolojik parçalanmaya uğramamaları nedeniyle çevrede ve canlı organizmada birikmeye meyillidir ve bu metaller zamanla etkin dozlara ulaşarak ciddi hastalıklara, hatta ölümlere yol açabilirler. Çevre ve insan sağlığı için çok tehlikeli olan ağır metallerin çeşitli ortamlardan uzaklaştırılmasının gerekliliği bilincine dünyaca varılmıştır. Bu konuda geniş araştırmalar yapılarak değişik yöntemler kullanılmaktadır. Ağır metallerin giderimi için en çok kullanılan yöntemler arasında kimyasal çöktürme, adsorpsiyon, flotasyon, iyon değiştirme, kimyasal oksidasyon-redüksiyon, tersakımlı ultrafiltrasyon, ters osmoz ve çimentolaştırma sayılabilir. Çalışmamızda çeşitli kil mineralleriyle, atıksudan adsorpsiyon yöntemiyle kurşun giderimi incelenmiştir. Adsorbant olarak kil minerallerinin kullanılmasının amacı killerin genel olarak çok ucuz maddeler olması ve bu amaçla ülkemizde kullanımının ekonomik olabilirliğidir. Bu çalışmada üç çeşit kil kullanılmıştır. Ülkemizin iki farklı bölgesinden elde edilen iki çeşit bentonit (Gebze ve Enez) ve kaolin bu çalışmada kullanılan killerdir. Adsorpsiyon deneyleri kesikli sistemde gerçekleştirilmiştir. Ünce kil dozu değişiminin kurşun giderim verimine etkisi incelenmiştir. Uygun kil dozunu belirlemek için 10 mg/L konsantrasyonda kurşun içeren çözeltiye farklı dozlarda Bentonit- Enez(BE), Bentonit-Gebze(BG) ve Kaolin(KA) ilave edilmiştir. Bu deneyler sonucunda en iyi verimin elde edildiği dozlar belirlenmiştir. Bu dozlar BE için 4g/L, BG için 15g/L ve KA için 15g/L'dir. Daha sonra belirlenen uygun kil dozları kullanılarak, başlangıç kurşun konsantrasyonunda yapılan değişikliklerle, başlangıç kurşun konsantrasyonu değişiminin adsorpsiyon verimine etkisi incelenmiştir ve en iyi verimin elde edildiği başlangıç konsantrasyonun her bir kil için tespit edilmiştir. Üçüncü aşama olarak, belirlenen uygun kil dozları kullanılarak, başlangıç konsantrasyonunu da belirlenen değerlere ayarlamak suretiyle yalnızca çözeltinin pH 'sini değiştirerek en iyi verimin elde edildiği pH aralıktan belirlenmiştir. Elde edilen sonuçlardan BE ve BG'nin kurşun adsorpsiyonunda KA `ya nazaran daha etkili okluğu tespit edilmiştir. Ayrıca pH değişiminin de adsorpsiyon üzerinde etkili okluğu belirlenmiş ve pH 5-8 aralığında verimin yüksek olduğu gözlenmiştir. Çözeltideki kurşun konsantrasyonu artışı ile giderme veriminin azalma gösterdiği belirlenmiştir. Yapılan adsorpsiyon izotermi çalışmalarında elde edilen verilerin Freundlich izotermine uygun olduğu tespit edilmiştir. Sonuç olarak kil minerallerinin adsorpsiyonla kurşun giderimi için kullanılabilirliğinin düşünülmesi gerektiği sonucuna varılmıştır.
Özet (Çeviri)
The presence of heavy metals in the environment can be detrimental to a variety of living species. Heavy metals have toxical effects to the living bodies in disposal areas. The most important feature that distinguishes heavy metals from other toxic pollutants is their nonbiodegradability and that even have a tendency to accumulate in living cells. Therefore, the elimination of heavy metals from wastewater is an important subject for public health. According to some surveys from the Public Health Services of different countries, significant numbers of people have been exposed to the hazards of excess metals in different ways. Lead is naturally occuring constituent of plant and animal life and low background levels are present in biosphere. The primary examples of lead poisoning have resulted from industrial uses of the metal with toxicity noted - among both workers and their children. Children are often expose via dust transported from work when careful sanitatiton procedures are not followed. In addition to the use of certain lead-containing pottery glazes caused the lead to be leached into foods of moderate or high acidity, contributing to a continous intake of lead. This probably caused low-grade neurological symptoms, although not dead ; this hyphothesis is supported by the detection of high skeletal lead levels in the bones of individuals. In animal tissues less than 10% of the dietary lead is absorbed and 90% of the remained lead resides in the skeleton. Lead is eliminated through perspiration, hair, urine and the bile. Long term exposure to low levels of lead may present an additional health hazard when physiological stresses that resultin abnormally high calcium metabolism cause the mobilization of bone lead and consequent increases in circulating lead levels. Blood, kidneys and the nervous system are all sensitive to elevated levels of soluble lead. An important aspect of lead toxicity is the exposure to children. One avenue for this has been the transmission of dust from industries such as battery manufacturing via the workers' clothing to the home. Another results from past use of paints containing high levels of lead. Pica(ingestion by children of foreign substances such as dirt or paint chips) may lead to the consumption of lead-contaminated materials such as peeling paint. Since 1 cm2 paint chip may contain as much as 50-1 OOmg lead, a few chips a day may cause the intake of unacceptable doses of lead. It has been estimated that 50000 children have suffered from lead poisoning. Although physical recovery fromthis poisoning is possible, permanent damage and mental retardation may result because childern are most commonly exposed during the first 5 years of life, which are critical for brain growth and development. Some evidences indicate that exposure to lead at levels below those causing physical symptoms may result in permanent intellectual or behavioral deficits. Because lead appears to be the most common heavy metal contaminant, the solution of this problem is important. The exposure of children accounts for the major known health hazard of lead, other than accute poisoning in industrial workers. Many studies have recently been conducted on environmental release of tetraethyl lead used as an antiknock agent in gasoline. At the high operating temperatures of the internal combustion engines the lead salts are volatized and expelled with the exhaust gases. Some evidences suggest that areas near roadways have a higher than average axposure to such salts. Other sources have contributed to increased lead burdens in the environment. The disposal of used lead sulfate automotive batteries provides a constant source of the heavy metal from those batteries, that are not recycled. In addition to appearing as a component of industrial effluents, lead arsenate has been used as an agricultural pecticide. Many methods have been proposed for the removal of heavy metals. Chemical precipitation, membrane filtration, ion exchange, alum coagulation, iron coagulation and adsorption are some cf the most commonly used processes; each has its merits and limitations in applications. Chemical precipitation is the most used method for the removal of heavy metals. Heavy metals are generally precipitated at minimum soluble pH values by costic and lime as hydroxids. Floatation is another method that is used for the removal of heavy metals. Advantages of this method are easy to operate small area requirement, low sludge production and low costs. Ion exchangers are rarely used but very effective for heavy metal removal. This method has some disadvantages such as high operating costs. Another important alternative for chemical treatment of heavy metals is chemical reduction-oxidation reactions. Crossflow ultrafiltration (CFU) is nowadays used for the removal of heavy metals. This method have low operating costs and low area requirement. Microorganisms are also used for the removal of heavy metals. Many microorganisms can adsorb hazardous metal ions in sea water, industrial and municipal wastewaters and surface water. Some kind of algaes and bacterias are used for this method. Adsorption is another most important method in recent days. Adsorption involves the partitioning of a contaminant from one phase into another phase. Adsorption is the process by which ions or molecules present in one phase tend to condense and concentrate on the surface of another phase. There are three general types of adsorption; physical, chemical and biological adsorption. Physical adsorption is relatively nonspecific and is due to the operation of weak forces of attraction or Wan der Waals forces between molecules. Here, the adsorbed molecule is not attached to a particular site on the solid surface but is free to move about over the surface. Chemical adsorption, on the other hand, is the result of much stronger forces, comparable with those leading to the formation of chemical compounds, normally the adsorbed material formsa layer over the surface which has thickness of only ore molecule and the molecules are not considered free to move from one surface to another. When the surface is covered by the monomclecular layer, the capacity of adsorbent is essentially exhausted. The use of bacteria for the removal of heavy metals has being used for a long tine. In wastewater treatment processes bacterial heavy meta! removal have four mechanisms as physical-chemical adsorption, complex.formation, sedimentation and biological activation. Factors that effect adsorption are temperature, ph. particle size of adsorbent, surface area of adsorbent and initial adsorbate concentration. In water and wastewater, various chemical materials are used for different adsorption techniques. Activated carbon adsorption appears to be a particularly competitive and effective process for the removal of heavy metals at trace quantities. However, the use of activated carbon is not suitable in most cases for developing countries because of its high cost. For that reason, the use of low cost materials as media for metal removal from wastewater have been highlighted recently. These materials are industrial products such as wool, rice straw, coconut husks and peat moss. New researches show the effective adsorption of heavy metals from wastewater using agricultural products and by-products; walnut expeller meal, peanut skins, wool, rice straw, plumpit shells, peanut hults, sugar cane bagasse. Recently, the use of waste tea leaves and coffee powder for heavy metals removal has been reported as a succesful method. The aim of the present work is to study the effectiveness of the clay minerals such as bentonite and kaolinite on the removal of lead(ll). Three adsorbents were used in this study. Two kinds of bentonite that are obtained from two different regions of Turkey (Gebze and Enez) and kaolinite. Adsorption experiments were carried cut in batch system under various initial adsorbate concentration, initial pH values and adsorbant / adsorbate mass ratios. Lead analyses were carried out in UNİCAM 92S Model Atomic Absorption Spectrcphotometer(AAS). Batch system contains a shaker. For the determination of clay dosage for the best removal efficiency, 10 mg/L initial lead concentration prepared and seven various dosage of Bentcnite-Enez clay were added to the solutions. And this procedure was also applied for Bentonite-Gebze and Kaolinite. During the experiments, samples were teken and lead concentrations was analysed by Atomic Absorbtion Spectrcphotometer(AAS). With the determined Bentonite-Enez, Bentonite- Gebze and Kaolinite dosages (4 g/L, 15 g/L and 15 g/L) and with various initial lead concentrations, experiments were carried out for the determination of the effect of initial adsorbate concentration to the removal efficiency of lead. For this experiments initial lead concentrations between 1- 100 mg/L were used for Bentonite-Gebze and Kaolinite 3nd 10-50mg/L for Bentonite-Gebze. Lead analyses were done for samples that are taken during the experiments. Optimum clay dosage and the effect of initial lead concentration for the removal of lead from solution were determined. And at the third stage, the effect of pH on the removal efficiency was determined.For this experiments, determined clay dosages and three various initial lead concentrations that give best efficiencies were used and this solutions were adjusted to the pH values between 1-10. For Kaolinite between 4-5mg/L initial lead concentration and 15.g/L dosage approximately 70-75% lead removal efficiency is satisfied, for Bentor.ite-Gebze with initial concentration cf 14-18rrg/L and 15.g/L dosage approximately 90-95% efficiency and for Bentonite-Er.ez initial concentration of 4-8 mg/L and 4 g/L dosage 95% efficiency is obtained. Removal efficiency is increased with the increasing pH values. Especially at the pH values between 5-8 for Kaolinite 70-90%, for Eentonite-Gebze 90- 95% and for Bentonite-Enez 70-85% removal efficiency is satisfied. These results show that the equilibrium adsorption capacity varied with dcsage, pH and initial adsorbate concentration. As a result adsorbtcn of Pb(Il) on clay minerals seems to be applicable for the treatment of wastewater. All the data which are determined during the removal of lead by clay minerals were examined according to the Langmuir and Freud.ch isotherms. The Langmuir Isotherm is used to describe single-layer adsorption and can be written as follows: C 1 1 ( ) q qm K qm Freundlich studied the adsorption phenomenon extensively and showed that adsorption from solutions could be expressed by the equation; 1 log q = log k +¦ - log C n Accordaig to this equations Isotherm constants are calculated and given in the tabei. It is seen that obtained data in accordens with the Freundlich isotherm.Tabel 1.Freundlich Isoterm Constants Tabel 2.Langmuir Isoterm Constants
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