Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Preparation of Acrylic Monomer Based Nanocomposite Hydrogels and Their Applications

Superabsorbent hydrogels are loosely crosslinked hydrophilic polymers that can absorb, swell and retain a large volume of water or other biological fluids. Because of their superior properties they have hygienic, agricultural, medical and pharmaceutical applications and in such applications, water absorbency and water retention properties are essential. In recent years, the preparation of organic-inorganic superabsorbent composites are called nanocomposites has attracted great attention because of their relatively low production cost, high water absorbency and their considerable range of applications in agriculture and horticulture, so these systems have become increasingly popular. Because of their hydrophilic nature, natural abundance and low cost, clays of smectite group such as attapulgite, sepiolite, montmorillonite are used as inorganic compound. Polymer-clay nanocomposites frequently exhibit excellent physical, mechanical and other properties, compared to those of pure superabsorbents or conventional superabsorbent composites. It is attributed to the nanoscale dispersion of clay in the polymer matrix, high aspect ratio of clay platelets and interfacial interaction between clay and polymers. In the last several years, researchers have focused on studying the synthesis and characterization of acrylic based nanocomposite superabsorbents.

In modern industrial society, dyes are used everywhere such as textile, paper, plastics and cosmetic industries. Therefore the removal of dye molecules from waste waters is a matter of great interest in the field of water pollution. Several physical, chemical and biological water treatment processes such as coagulation-flocculation treatment, biodegradation processes, oxidation methods, membran filtration and adsorption have been proposed for the removal of dyes from plastics, dyestuffs, paper and textile effluents. Because of the high effiency, easy handling and availability of different adsorbents (for example solid or hydrogel), among these numerous techniques, adsorption technique is generally preferred as an high effective and useful process.

The aim of the study presented these thesis is that the preparation of nanocomposite hydrogels with amphoteric structure and the investigation of the efficiency in the removal of the acidic dye indigo carmine from the aqueous solutions.

Two groups expriments were realized. In the first group experiments, acrylic monomer based nanocomposite hdyrogels with amphoteric structure were obtained and characterized. Firstly, these nanocomposite hdyrogels (NH) by using the same amounts of acrylic acid (AA) as an acidic monomer, 2-(diethylamino)ethyl methacrylate (2-DEAEMA) as an cationic monomer, potassium persulfate-bisulfite as initiator and different amounts (1,3,5,7,10 % of total monomer weight) of montmorillonite (MMT), according to the free radical addition polymerization mechanism and in-situ polymerization technique in the aqueous media. Prufied products were characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and X Ray Diffaction (XRD) techniques. The formation mechanism and the structure of the NH’s were clarified. Swelling behaviours in the distilled water and in the solutions with different pH values, swelling kinetic and mechanical properties (elastic module) of the products were investigated. The results of obtained data were determined that equilibrium swelling degree of the NH decreases with the increase of the amount of the MMT, but the mechanical strength increases, also swelling properties of the NH is sensitive to the pH values of the solutions.

The second group experiments are the applications of the removal of the indigo carmine from aqueous solutions. Dye adsorpsion depending on the time and the adsorption kinetic and the isotherm of the products were investigated in these group experiments. From the adsorption data, it was determined that adsorption rate increases with the increase of the amount of the MMT, adsorption or all produts fits pseudo-first-order kinetic model and for selected product NH5 also fits all isoterm models (Langmiur,

Freundlich and BET).