Synthesis and Characterization of Chitosan and Graphene Oxide to Form a Nano-Composite Hydrogel for the Removal of Heavy Metal Ions

Abstract

Chitosan is a natural polymer that has proved its uses in many research areas because of its wide range of properties specially its adsorption properties can purify water by sticking metallic ions to its surface. In the present study local bio waste of shrimp shells was converted into chitin and then to chitosan. Chitosan was extracted by the combination of different processes. Shrimp shells were dried, soaked in 4% NaOH solution for 20 h, soaked it in 4% HCl solution for 10 h, again treated with NaOH but with 2% concentration for 24 h, soaked in 1% HCl for 12 h and washed with distilled water. Treatment with NaOH deprotienize the shrimp shell and HCl is supposed to demineralize the sample. Deprotienized and demineralized samples were then decolorized with 1% KMnO4 for 1 h. Sample was then treated by it 1% oxalic acid for 3 h. Decolorized sample, called chitin is brilliant white in color was soaked in 65% NaOH solution for around 70 h and the chitosan was extracted. Graphene oxide was also synthesized separately. The chitosan-graphene oxide hydrogel was prepared by socializing graphene oxide sheets and chitosan chains. The FTIR results showed the characteristic peaks of chitosan while UV-Vis spectroscopy of graphene oxide also confirmed the formation of graphene. The hydrogel obtained from CS-GO was also characterized through XRD and FTIR spectroscopy. Different samples of wastewater from industries, as well as self-prepared sample of copper sulphate, zinc chloride, and nickel sulphate were treated with the CS-GO hydrogel to reduce the contaminations in water. The hydrogel was simply poured in water and water was shaken, it was found that all the colored solutions were either became transparent or their transparency was increased due to the treatment with CS-GO hydrogel. It proves that the CS-GO successfully reduced the concentration of contaminants from waste water and a visible change of color was seen in the samples. The UV-VIS spectroscopies were also performed on all samples and a remarkable increase in transmittance was observed in all samples treated with CS-GO hydrogel.