Browsing by Author "Jayawardena, C.L."

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item: Conference-Full-text
Experimental synthesis of zeolites from pre-processed coal fly ash using the microwave irradiation method
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Amirthavarman, V.; Perera, A.W.B.M.; Madhuwantha, G.L.S.; Fernando, W.A.M.; Jayawardena, C.L.; Wickrama, M.A.D.M.G.; Iresha, H.; Elakneswaran, Y.; Iresha, H.; Elakneswaran, Y.; Dassanayake, A.; Jayawardena, C.
Coal power plants contribute by an excess of 40% to the generation of electricity worldwide. Coal fly ash (CFA), being a dominating by-product of coal power generation, is unique due to its physicochemical properties such as thermal stability, chemical inertness, compressive strength, and adsorption. However, reducing the inherent impurities of CFA, which is heterogeneous, has proven to enhance its ability to be valorised into different second-generation products of high value. Pre-processing has been a successful method in eliminating impurities of CFA, and washing cycles method is the preprocessing technique used in this study. Zeolites, a second-generation product from CFA, are well known for their excellent adsorption properties due to their high surface area and porosity, being an optimal solution for wastewater treatment. Also, the microwave irradiation method has proven to be useful and rapid in synthesising zeolites. This study investigates the effect of pre-processed CFA obtained through optimised utilisation of wash cycles, compared to raw CFA, and the feasible conditions of zeolite synthesis from CFA which have undergone the wash cycle preprocessing technique. NaOH concentration and microwave irradiation power were considered as key parameters. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) were utilised to verify the enhanced nature of CFA after pre-processing, and formation of zeolites. The results of XRD infer that Mullite (Al4+2xSi2-2xO10-x) is the major crystal match for CFA obtained from the site. Also, pre-processed CFA yields a better qualitative phase analysis with Mullite than raw CFA, with the former having a peak coverage of Mullite that is approximately three-fold than the latter. Furthermore, according to the experimental results, zeolite L and zeolite Na-Y were produced from the process, having an optimal NaOH concentration of 2.5M and microwave irradiation power of 300W. These findings have been corroborated using XRD and SEM with EDS analyses, and we recommend further extension of the frontier to check the viability of zeolite formation with other critical parameters, paving way to an effective treatment of wastewater.
item: Article-Full-text
Leaching of rare earth elements (REEs) from lake sediments around Eppawala phosphate deposit, Sri Lanka: A secondary source for REEs
(Elsevier, 2021) Dushyantha, N.P.; Ratnayake, N.P.; Premasiri, H.M.R; Ilankoon, I.M.S.K; Hemalal, P.V.A.; Jayawardena, C.L.; Chandrajith, Rohana; Rohitha, L.P.S.; Abeysinghe, A.M.K.B.; Dissanayake, D.M.D.O.K.; Dharmaratne, P.G.R.; Ratnayake, A.S.; Batapola, N.M.
Rare earth elements (REEs) are widely employed in a spectrum of high-tech applications. Since primary REE resources are limited, secondary REE sources will be crucial to reduce future supply chain gap between REE demand and supply, which is currently about 3000 t per year. In this context, lake sediments around Eppawala Phosphate Deposit (EPD) in Sri Lanka could be considered as a potential secondary REE source since a man-made water canal running across the EPD transports REE-rich materials to the lake sediments. The average total REE (ΣREE) concentration of the downstream surface lake sediments was 804 mg/kg. The REEs were present in lake sediments as 3 fractions, namely, ion-adsorbed, colloidal, and mineral bound fractions. Ion-adsorbed fraction was assessed using less expensive, easy, and environmentally friendly ion-exchangeable leaching by a solution of (NH4)2SO4 under optimum conditions. Experimental results revealed that 34% of ΣREE was leached as ion-adsorbed fraction. In addition, the maximum leachable REE content (i.e. ion-adsorbed and colloidal fractions) was determined as 78% of ΣREE through HCl leaching under optimum conditions. Therefore, acid leaching was proven to be the best leaching process and the results in this preliminary study could be useful to assess low-grade geological resources, especially sediments and soils around major phosphate deposits with similar geological settings.
item: Conference-Abstract
A predictive model derived from sattellite data and selected water quality parameters for invasive plant dynamics in north Bolgoda lake
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Gowsiga, A.; Kayooran, S.; Sriyasantha, P.D.S.H.; Gohulan, H; Dassanayake, D.M.S.M.; Jayawardena, C.L.; Iresha, H.; Elakneswaran, Y.; Dassanayake, A.; Jayawardena, C.
The proliferation of aquatic weeds and algae in water bodies, such as Water Hyacinth coverage in North Bolgoda Lake, underscores potential pollution concerns associated with prolonged plant growth on surface water, changing nutrient levels and subsequently the water quality. This study aims to develop a regression model employing remote sensing techniques to identify and map the spatial distribution of invasive plants, primarily Water Hyacinth, in North Bolgoda Lake. Integration of surface temperatures derived from the Thermal Infrared (TIR) band of Landsat-8 satellite data facilitated by the field measurements of selected parameters are the main components of this research. Utilizing TIR band 10 data, converted into Lake Surface Water Temperature (SWT) imagery, alongside the surface water temperature measurements from pre-identified locations and computed Dissolved Oxygen (DO) and Chemical Oxygen Demand (COD) values for the same locations includes the main data used for the study. Lake SWT and DO, COD gathered from 30 locations during February and March 2024, revealed a linear inverse correlation between Lake SWT, COD, and DO. A composite map was generated for the selected locality of the North Bolgoda Lake with all the above information including provisions for precision enhancements by continuing insertion of field data. Despite the involvement of limited parameters this dynamic map could serve as a preliminary model for recognizing the behaviour of invasive plants and their impact on the selected elements of the waterbody. Further, this could be extended to determine the lake bottom dynamics, behavioural characteristics of the water column and the potential for encountering contaminations. It is recommended to develop this map by including further parameters and replicate the same methodology to cover the North Bolgoda Lake extent to assist authorities to make informed decisions. This study merges the satellite-derived data with ground-truth measurements to validate and refine the predictive models, ensuring their accuracy and reliability in forecasting. Utilizing spatial autocorrelation techniques this predictive framework could be further improved.
item: Conference-Abstract
A Statistical analysis of urban location data obtained from smartphones for disaster response
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Jayasundara, D.R.T.; Kularatne, M.K.B.D.; Samarakoon, K.G.A.U.; Jayawardena, C.L.; Iresha, H.; Elakneswaran, Y.; Dassanayake, A.; Jayawardena, C.
Technological advancements in device hardware and application software platforms have enabled smart phones to be used for multiple purposes as an all-in-one hand-held device. Its readily availability among majority of individuals, ease of use as a compact unit with access to remote storage and capacity to communicate makes it a perfect tool for emergency response specially with reference to disaster management provided having sufficient reception. Nevertheless, its embedded location services facility which communicates with the GNSS not only facilitates navigation, location sharing etc. but also capable of producing geo-tagged information, which could be vital under emergency conditions. Hence, this study statistically evaluates the reliability of location data recorded from a combination of smartphones and hand-held GPS units under selected urban environmental conditions. Commonly available four devices and a combination of applications were performed at five locations over a period of two months as the data collection for this exercise. The results reveal, regardless of the device and software combinations the location readings approximately follow the Gaussian distribution. However, a varying functionality has been observed in certain locations despite the consistency in environmental factors. Also, the mobile phones demonstrated a reasonable consistency among them in most of the horizontal positioning coordinate display events, despite the differences extracted from statistical analysis. Except in one location the smartphones indicated a significant difference in linear location data when compared with those obtained by handheld GPS. Analysis of Variance (ANOVA) was conducted to test the differences at 5% significance level. There is a growing emphasis on capturing records of geo-tagged spatio-temporal data not only to enhance the smartphone user experience but also for the disaster response considering the capability of smartphone to determine positions. Through this research, valuable insights into the performance of smartphones as tools for spatial data collection are sought to be provided, and best practices for location-based applications are aimed to be informed.