IRSPAS 2019
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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 Assessment of groundwater contamination with environmental toxicants in CKDu endemic area, Polonnaruwa, Sri Lanka(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Perera, W. P. R. T.; Dayananda, M. D. N. R; Botheju, W. S. M.; Liyanage, J. A.Chronic Kidney Disease unknown etiology (CKDu) is one of the major health impacts predominantly confined to people in North Central Province in Sri Lanka. The root courses for the disease prevalence have not found yet. Therefore, this investigation was carried out to determine the groundwater contamination with environmental toxicants: Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Zinc (Zn), Arsenic (As), Iron (Fe), Calcium (Ca), Magnesium (Mg) Fluoride (F), Sodium (Na) and Aluminium (Al) in Dimbulagala Grama Niladhari Division (GND) in Polonnaruwa District, Sri Lanka. The study investigated the groundwater quality of Dimbulagala GND in dry zone of Sri Lanka to assess its suitability for drinking purposes. Only Ten working tube wells were found in the studied area and groundwater samples were collected from the tube wells. Basic physicochemical parameters (pH, temperature, conductivity and dissolved oxygen), (Hatch HQ14d) and fluoride content were determined (Orion Star- 2014) onsite. Environmental toxicant concentrations were determined using Inductive Coupled Plasma Mass Spectrometry (ICP–MS, Agilent 7800). Results were analyzed using SPSS statistical software. descriptive statistics were performed on the data set and the Pearson correlation was applied. According to the results obtained from the onsite investigations the mean values of pH, conductivity and fluoride content were 7.78 (+1.28), 520 us/cm (+148) and 1.20 mg/l (+0.32) respectively. The mean value of the fluoride content has exceeded the permissible limit (1.0 mg/L), (SLS 614-2013). It was highlighted that significant toxic heavy metals such as Lead (Pb), Cadmium (Cd), Chromium (Cr) and Arsenic (As) levels as well as other metals like Fe, Cu, Zn, Na, Al have not been exceeded than permissible limits (SLS 614-2013). Statistically evaluation process proved none of the positive correlation is reported between heavy metal concentrations and Fluoride content of the groundwater in the studied area. But a negative correlation was reported between Fluoride and Cr (p= -0.05) in the groundwater in the studied area. Ca and Mg concentrations ranged between 3.43 mg/l to 130.56 mg/L And 6.54 mg/L to 75.32 mg/L respectively. Although mean Ca (10.12 mg/L) and Mg (15.45mg/L) did not exceed the permissible levels (100 mg/L and 30 mg/L for Ca and Mg), 40% and 50% of individual samples for Ca and Mg levels exceeded the permissible levels respectively. There is an urgent need for establishing proper long term drinking water treatment method for the studied area because of long term exposure to heavy metals such as Cd, Pb, Cr, As, and high levels of Fluoride as well as other environmental toxicants can be harmful to people. These findings can be used as a benchmark of raw water quality in the design processes of treatment plantsItem Investigation of spatial distribution of fluoride in drinking water sources in CKDu prevalence areas in Sri Lanka using GIS(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Dayananda, M. D. N. R.; Botheju, W. S. M.; Perera, W. P. R. T.; Liyanage, J. A.Chronic Kidney Disease of unknown etiology (CKDu) has identified as a significant health burden in rural dry zone areas in Sri Lanka. Fluoride is recognized as a nephrotoxic contaminant which deteriorates the renal functions progressively and the drinking water could be the major source which is responsible for the disease occurrence. Therefore, the present study attempted to investigate the spatial distribution of fluoride in drinking water sources in CKDu prevalence hotspots in Sri Lanka using Geographical Information System (GIS). Triplicated drinking water samples were collected from 30 sampling locations (from dug wells) in each Grama Niladhari Division (GND) including Wewelketiya GND in Anuradhapura district, Ambagaswewa GND in Polonnaruwa district, Naminigama GND in Mathale district and Buddhangala GND in Ampara district (Reference site) in dry season, Sri Lanka (February – March, 2019). Fluoride contents of collected samples were analyzed using ion chromatography (Metrom Eco_IC instrument). Spatial distribution patterns were interpolated using inverse distance weighted (IDW) and spatial autocorrelation (Moran’s Index- MI) tools in ArcMap 10.2.2 software. Results indicated that the mean fluoride levels of the collected water samples of Ambagaswewa and Wewalketiya areas were 1.37 ± 0.66 mg/L and 1.26 ± 0.65 mg/L respectively and those results exceeded the Sri Lankan drinking water standards (SLS 614: 2013) (1.0 mg/L) but the mean fluoride levels relevant to Naminigama area (0.82 ± 0.59 mg/L) complied with the SLS standards. Further 80% of the samples in Ambagaswewa GND and 95% of samples in Wewalketiya GND were highly contaminated with fluorides which were exceeded the SLS standard limits. Significantly higher Fluoride concentration levels were shown in Ambagaswewa GND (P= 0.103) and Wewalketiya GND (P= 0.704) compared to the reference area of the study.As well as fluoride concentration of the reference area was evenly distributed (MI= -0.005) in very low levels compared to the selected hot spots. Fluoride distribution were clustered with higher levels (MI = 0.31) in Wewalketiya GND, and Fluoride levels were evenly distributed with higher levels in Ambagaswewa GND and Naminigama GND with the Moran’s Indices of -0.12 and -0.07 respectively. It can be concluded that fluoride can be one of the risk factors affecting the prevalence of the CKDu. As the people are at a risk with the long-term exposure to the high fluoride concentrations, it is very essential to innovate a proper and affordable drinking water treatment technology for the affected areas and findings of this study can be used as background water quality data in the design processItem 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.