Preparation and characterization of cross-linked graphene oxide-based composites for adsorption-based applications

Abstract

Increasing activities in industry have resulted in wastewater generation that contains contaminants. Therefore, several methodologies have been developed to manage wastewater pollutants in which adsorption technology using graphene-based materials may offer an approach for efficient wastewater remediation. This Ph.D. thesis describes the synthesis and characterization of graphene oxide (GO)-based composites for adsorption-based applications. In the present study, chitosan (CTS) and aluminum ions (Al3+) as cross-linkers were utilized to enhance physical properties, mechanical performance and adsorption properties of GO by use of a solution-based method. The adsorption properties of samples were studied in solution and in the gas phase. Also, structural, morphological, physical, ion permeability, and mechanical properties of the GO and GO-based composites were studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), ion permeability determination and dynamic mechanical analysis (DMA), respectively. Mechanical properties of GO upon addition of cross-linkers were analyzed statistically by means of analysis of variance (ANOVA). Interaction of CTS and Al3+ ions with functional groups of GO sheets were supported by changes in surface charge of the GO sheets and spectroscopy techniques. SEM results showed that cross-linking of GO changes its porosity and layered morphology. The TGA results revealed that the GO-based composites exhibited a gradual weight loss which started at higher temperatures as compared with GO due to cross-linking effects. In addition, it was found that the swelling degree of GO reduced and was demonstrated to be more stable in water upon cross-linking. The sorption properties of GO in solution and the gas phase were found to remarkably improve upon formation of a GO-based composite. The results of Ion permeability tests indicated that GO composites had variable ion transport characteristics according to the changes in inter-layer spacing of GO sheets upon cross-linking. Additionally, the use of cross-linkers led to an increase in the mechanical properties of GO-based composites as compared with pure GO. ANOVA revealed that GO-based composites have a statistically significant enhancement in mechanical properties over pure GO. Therefore, GO-based composites prepared via cross-linking GO sheets have great potential for use as an alternative adsorbent and/or membrane for adsorption-based applications.