Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Preparation of The Starch Based Nanocomposite Hydrogels and Their Applications

Starch is an abundant, inexpensive and fully biodegradable natural raw material. Chemical modification of starch via grafting of vinyl monomers is one of the most effective methods to provide desirable properties into starch.

Since the environmental pollution is increasing day-by-day due to the increase in industrialization and urbanization, hence, the need to reduce the pollution particularly in industries is important. Among the enviromental pollutions, heavy metal ions and dyes have gained relatively more significance due to their toxicity. Moreover, the colour of industrial wastes is very desirable harmful for water consumers. Therefore, colour removal from wastewater is a major enviromental problem.

In recent years, graft copolymers of natural polysaccaharides such as cellulose and starch have been used for this aim.

In this study, the graft copolymerization of acrylic acid (AA) onto starch was carried out with monomer/starch weight ratio=1,5, with cerium ammonium nitrate (CAN) as an initiator and N-N’-methylenebisacrylamide (NMBA) as a crosslinking agent, under nitrogen atmosphere. Sodium montmorillonite (MMT) was used as nanoparticles. Starch-graft-acrylic acid/MMT (N-g-AA/MMT) nanacomposite hydrogels were characterized by X-ray diffraction (XRD) and FTIR analysis. The effect of MMT content in nanocomposite hydrogels on the swelling behavior was investigated. Increasing the MMT/ monomer ratio up to 1% causes an increment in water absorbency, which indicates that MMT can improve the ability of water absorbency but further increase of MMT causes a decrease in water absorbency. The removal of safranine T from aqueous solutions using N-g-AA/MMT nanocomposite hydrogels was described.

Effects of various parameters such as treatment time, initial dye concentration, and amount of the MMT were investigated. Dye removal capacities of these hydrogels were determined by UV-vis- Spectrophotometer.

The effect of MMT content of S-g-AA/MMT superabsorbent hydrogels on the removal of Pb2+ and Cu2+ ions from aqueous solutions was investigated at pH=4.0 and metal ion removal capacities of these hydrogels were determined by Atomic Absorption Spectrophotometer (AAS). The results showed the order of the removal of metal ions was Cu2+ >Pb2+ . The Freundlich equations were fit equilibrium isotherms for both dye adsorption and ion adsorption.

Also, mechanical properties were tested. The results showed that mechanical properties of N-g-AA/MMT superabsorbent nanocomposite hydrogels increased with the increase in content of MMT.