2011 YÜksek lisans tez özetleri

Anahtar Kelimeler: sodyum aljinat, itakonik asit, aşı kopolimerizasyonu, ağır metal uzaklaştırılması.

The Preparation and Characterization of Alginate Graft Copolymers

Environmental pollution and the subjection of humans to heavy metals are increasing in recent years due to increase in their uses in various industrial processes and products. For that reason, the removal of heavy metal ions is very important for the environment and human health. Among the heavy metals, which are present, more than 20, the most harmful ones for the human health are Hg, Cd, Pb, As, Cr, Cu and Zn. Sodium alginate ( NaAlg ) is a natural polysaccharide and in non-toxic, biocompatible, biodegradable and bioadhesive in nature and it can be used in the applications of removal of dye and heavy metal ions from wastewater; the isolation of heat and noise reduction; and controlled drug release processes.

In this study, alginate graft copolymer (NaAlg-g-PIA) was synthesized by the grafting of itaconic acid (IA) onto sodium alginate (NaAlg). The synthesis of graft copolymer was performed in aqueous solution of alginate at 30 ^oC using CAN/HNO₃ as initiator system, , under nitrogen atmosphere during 6 hours. The effects of NaAlg, IA, CAN ve HNO₃ concentrations on the graft copolymerization were investgated and the optimum reaction condition providing the highest amount of grafting (%41) was determined to be, [IA]=0.24 M, [CAN]=2x10^-2 M ve [HNO₃]=6x10^-2 M for 1 g NaAlg. In addition the effect of crosslinking on the grafting, glutaraldehyde (GA) and hydroxyapatite (HA) were used as crosslinker. The synthesized graft copolymer (NaAlg-g-PIA) was used in the removal of Pb²⁺ and Cu²⁺ ions from aqueous solution under non-competitive conditions. It was determined that the metal adsorption capacity of graft copolymer (3,83 mmol Cu(II)/g polymer and 3,44 mmol Pb(II)/g polymer)is greater than that of NaAlg ( 2,08 mmol Cu(II)/g polimer ve 1,89 mmol Pb(II)/g polimer). The adsorption of heavy metal ions was investigated by Atomic Absorption Spectrometer (AAS). The grafting yield and the equilibrum swelling values of NaAlg-g-PIA copolymer in distilled water were also determined. The characterization of NaAlg-g-PIA and metal ion-adsorbed NaAlg-g-PIA copolymer, in other words, the adsorption of metal ion was also investigated by FTIR. FTIR spectra of NaAlg-g-PIA, about 1723 cm^-1 confirmed the grafting of IA onto NaAlg. Glass transition of both NaAlg and NaAlg-g-PIA could not be determined from their DSC curves. NaAlg-g-PIA was also characterized by XRD, SEM and EDS methods, and the regeneration of metal adsorbed NaAlg and NaAlg-g-PIA was performed. SEM and EDS studies revealed that NaAlg-g-PIA contains Ce⁴⁺ ions due to CAN used as initiator during the copolymerization, and Ce⁴⁺ ions can not be removed completely during the metal ion adsorption (this Ce⁴⁺ ion does not ion-exchange by Pb²⁺ or Cu²⁺ions). The regeneration percentage of NaAlg-g-PIA (average % 94)was found to be higher than that of NaAlg (average %82). The viscosity average molecular weight of NaAlg was determined (225000 g/mol) by using Ubbelohde viscometer.