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Item Synthesis and characterization of silica nanoparticles and graphene oxide/nanosilica composite(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Weerasinghe, M. A. S. N.; Liyanage, J. A.; Kumarasinghe, A. R.Ordinary sand is commonly used for water purification. Graphene oxide (GO) is capable of absorbing various water pollutants such as heavy metals and organic contaminants. The ability and the efficiency of water treatment process is proposed to be enhanced using silica nanoparticles and GO/nanosilica composites. Silica nanoparticles and GO/nanosilica composite were synthesized and characterized. Silica nanoparticles were synthesized using tetraethyl orthosilicate and following the sol-gel method. Graphene oxide was synthesized using the modified Hummers’ method. Silica nanoparticles, graphene oxide membrane and GO/nanosilica composite were characterized using Fourier Transform Infrared Attenuated Total Reflection Spectroscopy (FT-IR ATR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Absorption Spectroscopy (ED-XAS) and X- ray Diffraction (XRD). The size of silica nanoparticles was found to be in the range of 50-110 nm with SEM data, which confirms the synthesis of nano-sized silica particles. The sheet like structure with aggregated and folded surfaces of graphene oxide was observed in the SEM analysis of graphene oxide. The interphase between silica and graphene oxide was observed in SEM analysis of GO/nanosilica composite. FT-IR ATR data supported for the identification of functional groups of silica nanoparticles, graphene oxide membrane and GO/nanosilica composite. The peak at 1093cm-1- for asymmetric stretching of Si-O-Si bonds and the peak at 800 cm-1 for symmetric stretching of Si-O-Si bonds are characteristics peaks of silica. The peaks at 3441 cm-1 for the stretching vibration of hydroxyl groups, at 1739 cm-1 for the stretching vibration of carbonyl groups and at 1391 cm-1 for the stretching vibrations of epoxy groups are characteristics peaks of graphene oxide. The FT-IR ATR spectrum of GO/nanosilica composites showed peaks for both silica and graphene oxide. ED-XAS data showed the presence of corresponding elements in each samples. Data from ED-XAS of silica nanoparticles supported the presence of silicon and oxygen while the ED-XAS of GO/nanosilica showed that the presence carbon, oxygen, silicon as the main elements of the sample. XRD spectrum of silica nanoparticles showed a strong broad peak at 22.22 (2θ). A broad peak for silica was observed in the XRD spectrum of GO/nanosilica composite similar to the XRD spectrum of silica nanoparticles. The data from SEM, FT-IR ATR, ED-XAS and XRD confirms the successful synthesis of silica nanoparticles and GO/nanosilica compositeItem Novel membranes for treatment of water: Graphene oxide membranes cross-linked with metal cations(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Bandara, W. R. N. M.; Liyanage, J. A.; Kumarasinghe, A. R.Declining of water resources and rapid expansion of the consumption of water worldwide have led to the search of novel water treatment technologies that can provide a safe water supply to the mankind. Graphene oxide (GO), which is an oxidative exfoliation product of graphite, is an ideal candidate to be used as a new material for this purpose. However, GO sheets gradually disintegrate in water because of electrostatic repulsions between ionized oxygen containing functional groups. This research work explores the ways in which impart physical properties needed for GO sheets to overcome their inherent dispensability in water environment and to enhance the necessary stability by cation cross-linking. GO membranes cross-linked with unit amount of Al3+, Zn2+ and K+ shows greater stability in water compared to the unmodified GO membranes. Energy Dispersive X-ray Absorption (EDXA) analysis proves the incorporation of metal ions into the GO membrane. Accordingly GO membrane cross-linked with Al3+, Zn2+and K+ (1000 mg mL-1, 300 μL) has caused a surface composition of 0.14%, 0.14% and 0.13% respectively by weight of particular metal cation. Scanning Electron Microscopy (SEM) images confirm the cation cross linking since cross-linked GO membranes have a wrinkled surface morphology compared to unmodified GO membranes. According to FTIR-ATR spectrums of GO membrane cross-linked with Al3+, Zn2+and K+ (1000 mg mL-1, 300 μL, 2000 μL, 3200 μL) intensity of carbonyl and epoxy peaks have been decreased and peak positions have been shifted to lower wave numbers with the increase of cation concentration compared to unmodified membrane since the amount of freely available functional groups decrease as the cross-linker concentration increase. Following cross-linking with Al3+, Zn2+and K+ (1000 mg mL-1, 300 μL) elastic modulus of GO membranes has been increased by 191%, 173% and 147% respectively. Hence tensile testing analysis confirms the cation cross-linking in the in-plane direction. Also tensile testing analysis represents the presence of a linear relationship between charge density of the cross-linker and enhancement of mechanical strength as the charge density of the cross-linker increased the enhancement in the mechanical strength has been increased. According to X ray diffraction (XRD) analysis, there is no significant change in the interlayer spacing of GO membranes with and without metal ion cross-linking. This may suggest that metal ion intercalation via the stacking direction has not been taken place or it is non-homogeneous. Studies are underway in order to further investigate the relationship between charge density of the cross-linker and the enhancement in mechanical strength and the aqueous stability caused due to cation cross-linking of GO membranes.