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Item Development of sand/graphene composite and its application for MCPA pesticide adsorption from water(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Perera, W. P. R. T.; Ruwanthi, N.M.N; Perera, P. L. R. A.; Kannangara, Amila; Premarathna, W.A.P.J; Liyanage, J. A.; Kumarasinghe, A. R.This research endeavours to synthesize a novel adsorbent, sand/graphene oxide composite (MGO/S), achieved through the iterative deposition of graphene oxide layers on river sand employing a thermal annealing process. Scanning electron microscopic (SEM) and Fouriertransform infrared spectroscopy (FT-IR) characterization studies revealed the presence of a nonuniform graphene oxide coating on the surface of the sand and the incorporation of oxygenated functional moieties within the structure. Comparative evaluations show the heightened adsorption capacity of this new composite entity with alternative sorbent materials, such as activated carbon, graphene oxide, and sand to adsorb neutral 2-methyl-4-chlorophenoxyacetic acid (MCPA) pesticide molecule. To analyse the MCPA adsorption parameters, High-performance liquid chromatography (HPLC)was used (Solvent mixture - Acetonitrile: Distilled water (1:1); Flow rate - 1.5µLmin-1; Wave length - 275nm). The retention time for the MCPA was reported as 1.538s. The optimization studies and adsorption modelling were carried out, focusing on the adsorption of MCPA onto the M-GO/S. Accordingly, the optimum concentration, dosage, and contact time were 75 mg/L, 0.05 g, and 105 minutes respectively, at neutral pH values. The investigation of adsorption equilibrium isotherms has highlighted the Freundlich model's (multilayer adsorption) superior explanatory capacity in characterizing the adsorption phenomenon. Concurrently, the analysis of adsorption kinetics has demonstrated a favourable fit with the pseudo-second-order model (with a correlation coefficient denoted as 0.9754), implying a prevailing chemical sorption mechanism underlying the adsorption process. Although MCPA possesses either neutral or negatively charged (upon dissolution) surfaces, the M-GO/S composite exhibits significant adsorption capability towards MCPA. Consequently, the synthesized composite emerges as a viable candidate for effectively mitigating MCPA pesticide contamination from water.Item Study of aqueous calcium ion adsorption competence by coreshell adsorbent granules engineered from sand/graphene oxide nanocomposite(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Premasinghe, Niroshan; Perera, W. P. R. T.; Fernando, W. S. K.; Liyanage, Janitha A.; Kumarasinghe, A. R.In water treatment, sand unit processes are frequently used to remove turbidity. In order to enhanced the performance of the sand, a surface modification was done using graphite oxide. The core-shell granules were fabricated using graphite oxide coated river sand. Graphite oxide was derived from high purity vein graphite in Sri Lanka. Repeated coating of graphite oxide on the sand followed by low temperature (110 °C) thermal pyrolysis yield hierarchical core-shell structure where several layers of graphite oxide covered the sand particulates. Mineralogical and physicochemical characterization of the novel adsorbent was carried out by Energy Dispersive X-Ray attached to Scanning Electron Microscopy (SEM-EDX), Fourier-Transform Infrared Spectrometry (FTIR), and X-ray Powder Diffraction (XRD). The operational parameters such as contact time, initial calcium ion concentration, adsorbent dose and initial pH of the solution were evaluated in batch procedures at room temperature (26±2 °C) using Five time GO/sand combination which observed as the most effective combination for calcium ion removal from hard water. Characterization studies reveal that uneven coatings of graphene oxide present on the surface of Nanocomposite is containing oxygen-based functional groups (C-O, C=O, O-H) in addition to C-C groups. Optimization studies showed that, the most effective dosage of the adsorbent is 5.0 g with initial calcium ion concentration 50 mg/L. It appears that there was no significant effect on the calcium ion removal over a wide range of pH 4-10 and the process began to reach equilibrium after 20 minutes. Finally, super sand granules show high partiality towards calcium ions and it will be important for the treatment of the hard water and the multiple coated GO/sand combination can be used to regulate excess water calcium and turbidity simultaneously.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.Item Investigation of fluoride adsorption capacity of characterized graphene oxide based super sand(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Perera, R. T.; Pathirannehe, P. N. S.; Weerasooriya, R.; Kumarasinghe, A. R.; Liyanage, J. A.Sand is conventionally used in water treatment plants to control water turbidity. This research work was aimed for improving its performance using a chemical modification to remove other water contaminants as well. Thus improved substrate was designated as “Super Sand”. Super sand has proven to be a better adsorbent for the removal of fluoride from water. Fluoride is an essential constituent for human health and toxicity of the fluoride depends on the concentration of the fluoride in the drinking water source. The fluoride adsorption capacity of characterized super sand was determined. Graphene Oxide (GO) was synthesized using the modified Hummers method and then GO was coated with purified sand for the generation of super sand. Single GO coated super sand and multiple GO coated super sand were synthesized for the investigation of fluoride adsorption capacity. GO and super sand were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDXAS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis and surface titration. Surface titration curve depicted that surface charge of super sand vary with pH value of the medium. Between pH 4 to 7 it has a total positive charge and above pH 7 it has a total negative charge. In order to determine the fluoride adsorption process, isotherm studies were done for both single coated and multiple coated super sand. According to the isotherm studies, single coated super sand has the maximum fluoride adsorption capacity at 2 mg/L fluoride concentration and multiple coated one has maximum fluoride adsorption capacity at 3 mg/L fluoride concentration. Further optimization studies were also performed and finally it was proved that fluoride adsorption by the super sand follows the Langmuir isotherm model. Further, FTIR analysis of super sand and fluoride adsorbed super sand at different pH mediums depicted that adsorption process is a chemisorption process. However, FTIR peak patterns depend on the pH of the medium. Hence, it can be concluded that surface modified super sand is suitable for the fluoride removal from the fluoride contaminated drinking water.