Çinkonun perlit ve kitosan modifiye perlit ile adsorpsiyon ve adsorpsiyon özelliklerinin karşılaştırılması
Çi̇nkonun perli̇t ve ki̇tosan modi̇fi̇ye perli̇t i̇le adsorpsi̇yon ve adsorpsi̇yon özelli̇kleri̇ni̇n karşilaştirilmasi
Yazar: AYÇA ELMAS
Danışman: PROF. DR. GÜLHAYAT SAYGILI
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Mühendisliği Bölümü / Kimya Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Kimya Mühendisliği = Chemical Engineering

Özet:
Hızla ilerleyen sanayileşme ile doğru orantılı olarak miktarları giderek artan çeşitli endüstriyel atıklar çevre kirliliğine sebep olmakta ve toprak, su ve atmosfere karışarak canlı organizmaların yaşamını etkilemektedir. Özellikle endüstriyel atık sularda bulunan ağır metaller, organik kirleticilerden farklı olarak biyolojik olarak parçalanıp yok olmadıkları için organizmalarda depolanmakta, besin zincirlerine girmekte ve sınır değerleri aştığında canlı yaşamını tehdit edebilmektedir.
Çeşitli endüstriyel faaliyetler sonucu oluşan atık sular önemli ölçüde çinko bileşiklerini içermektedirler. İnsan sağlığına zehirli etkisi olduğu bilinen çinkonun vücuda alınması halinde, böbrekler, sinir ve üreme sistemleri, ciğerler ve beyin önemli ölçüde zarar görmektedir. Bu yüzden endüstriyel işlemler sonrasında açığa çıkan atık sular bir takım işlemlerden geçirilerek standartlara uygun hale getirilmelidir. Dünya Sağlık Örgütü (WHO) tarafından belirlenen içme sularındaki kabul edilebilir çinko iyonu derişimi (5 mg/L) dikkate alındığında, yüksek miktarda çinko iyonları içeren endüstriyel atık sulardan bu iyonların ekonomik bir yöntemle giderilmesi gerekmektedir.
Atık suların içerdiği ağır metallerin giderilmesi için, kimyasal çöktürme, ultrafiltrasyon, ters osmoz, iyon değiştirme, adsorpsiyon, solvent ekstraksiyonu ve biyolojik prosesler gibi çeşitli yöntemler uygulanmaktadır. Bu yöntemlerin birçoğunun yüksek yatırım ve işletme maliyeti, fazla enerji tüketimi ve karmaşık proses aşamaları gibi dezavantajları olması nedeniyle atık sulardan ağır metallerin gideriminde daha ekonomik yöntemlerin tasarlanması gerekmektedir. Atık sulardaki ağır metallerin adsorpsiyon yoluyla uzaklaştırılması, kullanılan adsorbanın cinsine bağlı olarak diğer yöntemlere oranla daha ekonomik ve etkin bir yöntem olarak karşımıza çıkmaktadır. Atık sulardan ağır metal gideriminde en verimli ve etkin yöntem olan adsorpsiyon, kısaca iki fazı birbirinden ayıran ara yüzeylerde gerçekleşen tutunma olayı olarak tanımlanmaktadır.
Çinkonun, perlit ve kitosan modifiye perlit tarafından adsorplanarak giderilmesi incelenmiştir. Adsorpsiyon mekanizmasının aydınlatılması için Langmuir, Freundlich, Temkin ve Dubinin Reduschkevich izoterm modellerinin deney sonuçları ile olan uyumu araştırılmıştır. Son olarak; kullanılan adsorbanların adsorpsiyon kapasiteleri karşılaştırılmıştır. Adsorpsiyon sürecinin, çözelti pH ının, adsorban miktarının ve başlangıç konsantrasyonunun adsorpsiyon vermini etkilediği görülmüştür.
En fazla adsorpsiyonu yaptığı süreç, pH, adsorban miktarı ve başlangıç konsantrasyonu belirlenmiştir. Adsorbanların adsorpsiyon verimi karşılaştırılmıştır.

Abstract:
The amount of various industrial wastes increases proportionally with the rapid industrialization and causes environmental pollution which negatively effects living organism by getting into the soil, water and atmosphere. Heavy metals, that are exist in industrial waste waters, are one of the most important contaminants. Heavy metal contaminants are present in the waste waters of metallurgical/metal manufacturing and electroplating, chemicals, printing, dye and paint, pulp and paper, textile, refinery and petrochemicals, leather, fertilizer, pesticides and other industries. Unlike most organic pollutants, the heavy metals present in industrial waste waters, do not undergo biological degradation and tend to accumulate in the organisms, thereby eventually entering the food chains. Thus, these contaminants threat the life if they increased beyond the permissible level.
Waste waters originating from different industries contain considerably high amounts of zinc compounds. The uptake zinc by human body cause severe damage to the kidney, nervous system, reproductive system, liver and brain. Therefore, some operations should be applied to reduced the heavy metal ion concentration to the standard limit values. The permissible ion concentration level in drinking water as set by World Health Organization (WHO) is 5 mg/L for zinc. 
Several methods, such as chemical precipitation, ultrafiltration, reverse osmosis, ion exchange, adsorption, solvent exraction and biological treatment, are often used to remove the heavy metals from waste waters. Because most of these methods have some disadvantages such as high investment and operating costs, high energy consumption and complicated operation steps, there is a need to design more economical methods for the removal of heavy metals from waste waters. 
Adsorption has been universally accepted as one of the most widely used methods for removing heavy metals from aqueous solution. Removal of heavy metals from waste waters by adsorption can be economic and efficient in comparison with the other methods depending on the on adsorbent used. On the other hand, adsorption effectively removes contaminants in waste waters with high solute loadings and even at dilute concentrations (<0.01 M). Adsorption is briefly a holding event realized between the surfaces from each other that set apart from two phases. The adsorption process is governed by a number of parameters that determine the efficiency level of an adsorbent. However, appropriate properties and cost of adsorbent materials are the key aspects for practical applications when dealing with heavy metal removal from waste waters. By the usage of the adsorbants perlite and chitosan modified perlite,the adsorption of zinc metal in is observed. And the experiment results are used in isotherm models such as Freundlich, Temkin, Langmuir and it is observed which model is more suitable for the system.Also the capasities of perlite and chitosan modified perlite is compared.Adsorption time interval, solution pH and initial concentration is observed as a parameter that affects the adsorption percentage.  
In this study, perlite and chitosan dispersed perlite were used as the adsorbent. Perlite is a naturally occurring dense glassy volcanic rock which includes mainly fused sodium potassium aluminium silicate (greater than 70%) and 3–5% water. Silanol groups can form on the perlite surface providing various adsorption properties. Chitosan, poly(D-glucosamine), is obtained by deacetylation of chitin. Chitosan is a natural biopolymer, hydrophilic, and has the ability to form complexes with metals. It is also a non-toxic, biodegradable and biocompatible material. It contains primary amino groups, which are useful for chemical modifications. In this study, batch studies were performed to investigate the effects of various experimental parameters on zinc removal such as pH, initial zinc concentration, contact time, adsorbent ratio. Equilibrium isotherms of batch system were also analyzed by Langmuir, Freundlich, Temkin and Dubinin-Redushkevich isotherm models.
In this study, chitosan was dispersed on perlite to enhance the accessibility of OH and amine groups for adsorption of zinc  ions. Chitosan coated perlite was prepared as spherical beads. Batch studies were performed to investigate the effects of various experimental parameters on zinc removal. From 0.5g/L to 12.5 g/L perlit and chitosan dispersed perlite were used  as adsorbent to find the optimum  zinc  removal. Contact time experiments were run between 3-72 h. pH experiments were run between pH 4-10. To obtain the adsorption isotherms, initial zinc solution concentration was changed between 0.005-0.04 M. Zinc concentrations were measured by spectrophotometer (Jenway 6305 UV Spectrophotometer) according to zincon method.
The amount of ions retained in the adsorbent phase at equilibrium qe (mg/g) was calculated by using the following equation

qe=[((C_0-C_e ))/M]*V
The adsorbtion capacity was calculated by using the following equation
%Adsorbtion =( 1-Ce/Co)*100
where C0 and Ce are the initial and final concentrations of ions in solution (mg/L), M is the mass of the adsorbent (g) and V is the volume of the solution (L). 
Langmuir, Freundlich , Temkin and Dubinin-Redushkevich isotherm models have been employed extensively by many researchers to explain the adsorption mechanism of Zn+2 ions due to their simplicity and applicability. Therefore, the fitting between the experimental results and Langmuir, Freundlich and Temkin, Dubinin-Redushkevich isotherm equations were studied to describe the adsorption mechanism.
Adsorption capacity of perlite was found %54 according to zincon method. 72 h end-over-end shaking was enough to reach the adsorption equilibrium. The maximum zinc adsorption was occurred at pH 7.5-8.0. Whereas with chitosan dispersed perlite, zinc was adsorbed at the range of %78 and zinc adsorption with chitosan dispersed perlite was reached maximum at pH =5.5-6. Zinc adsorption isotherm was obtained by changing the initial zinc concentration. Temkin isotherm model was fitted well with experimental parameters for both of the adsorbents. Maximum zinc uptake was found 1197 mg/L and 1941 mg/L for perlite and chitosan dispersed perlite, respectively
.Maximum zinc removal was observed in the presence of chitosan dispersed perlite. Temkin isotherm model described well zinc removal on the both perlite and chitosan dispersed perlite single layer zinc adsorption. Chitosan coated perlite was showed higher zinc adsorption compared with perlite.