International Research Conference of UWU-2021

Permanent URI for this collection

https://erepo.lib.uwu.ac.lk/handle/123456789/8715

Browse

Browsing International Research Conference of UWU-2021 by Subject "Applied Earth Sciences"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Defluoridation of Groundwater by Electrocoagulation: Performance Evaluation of Electrodes
    (Uva Wellassa University of Sri Lanka, 2021) Yathushan, R.; Cooray, J.T.
    Fluoride dissolves in groundwater due to water-rock interaction and human activities. Drinking water with a low or high level of fluoride can cause adverse health effects to humans. Sri Lankan drinking water standard for fluoride is 1.0 ppm but, most of the groundwater from dry zone areas of the country exceeds this level while some even exceed 5.0 ppm. Electrocoagulation is one of the best methods that can be used to remove excess fluoride from drinking water. During this study, the performance of different metal electrode pairs, the dependence of initial pH, the retention time of process, the effect of pH variation, applied voltage and conductivity were studied concerning the removal of fluoride. Al-Al, Fe-Fe and Al-Fe were chosen for performance evaluation of electrodes. At the same time, initial pH was varied from 6.5 to 8.0 by 0.5 uniform intervals, and samples were taken in each 30 minutes intervals up to 4 hours in all experiments to determine the removal efficiency. The fluoride concentration of samples, were determined by UV Spectroscopy. DI water with 10 ppm fluoride was used for all experiments and during this process voltage, conductivity, current density, electrode separation distance and effective area of electrodes were maintained at constant. Al-Al electrodes showed better performance at 7.0 pH in a low retention time of 90 minutes and Fe-Fe electrodes were effective at 8.0 pH in a high retention time of 120 minutes. Natural groundwater with a higher concentration of fluoride (5.36 ppm and pH 7.98) was tested using Al-Al electrodes. After 2 hours of process, fluoride concentration was reduced to less than 1.0 ppm level, for Fe-Fe electrodes more time was required than Al-Al electrodes. During the procedure, pH was stable for Fe-Fe electrodes, but for Al-Al electrodes, pH value was increased more than 8. Al-Al electrodes can be effectively used for defluoridation of groundwater in Sri Lankan arid zones. Keywords: Defluoridation; Groundwater; Electrocoagulation
  • No Thumbnail Available
    Item
    Development of Green Colour in Topaz Using Diffusion Method
    (Uva Wellassa University of Sri Lanka, 2021) Shamal, Y.P.N.; Jaliya, R.G.C.
    Topaz is one of the abundant gem varieties in Sri Lanka with the chemical formula of Al2SiO4(F, OH)2, which has a hardness of 8 on the Moh’s hardness scale. The colourless Topaz varieties have less market value compared to the coloured Topaz varieties. Irradiation and other methods are used traditionally to improve the appearance of Topaz. Nevertheless, conventional methods have drawbacks such as high manufacturing cost, less operational safety due to radioactivity related processes. Hence, the present study tested the diffusion effect of Chromium (II) chloride on colourless topaz with the aid of heat treatment. Seventy-two colourless Topaz samples were treated with Chromium (II) chloride. The selected stones were heated under reduced and oxidizing conditions with the Chromium (II) chloride at different temperatures (600 0C, 700 0C, 800 0C, and 900 0C ) and different soaking times (1, 2, and 3 hours). In both reduced and oxidizing conditions Chromium (II) chloride, diffused into the topaz by producing a shade of pale green to dark green colour. Colour shade becomes strong with the increase of the temperature. Produced colours created a desirable appearance on the stones. At 900 0C the produced green colour was identified as ‘GB/BG 7/2’ in the GIA colour grading system. The durability of the coating was tested for acidic conditions (with HNO3 and H2SO4 acids) and sonication. The produced surface coating was stable under acidic conditions as well as under the sonication. Oxidizing conditions in electrically operated furnace is economically beneficial over gas furnace in producing colours. Finally, colourless Topaz could develop the green colour by diffusion with the optimum temperature of 900 0C with the soaking time of 1 hour under oxidizing conditions. Keywords: Diffusion Treatment; Topaz Enhancement; Colour development of gemstones
  • No Thumbnail Available
    Item
    Geochemical Variations of Prospective Heavy Mineral Deposits Bordering the Coastline of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2021) Subasinghe, H.C.S.; Ratnayake, A.S.; Wijewardhana, T.D.U.; Sameera, K.A.G.
    Heavy minerals with a specific gravity greater than 2.9 g/cm3 such as ilmenite (FeTiO3), rutile (TiO2), leucoxene (altered ilmenite), zircon (ZrSiO4), monazite ((Ce,La,Nd,Th)PO4), garnet ((Ca,Mg,Fe,Mn)3(Al,Fe,Mn,V,Cr)2(SiO4)3), sillimanite (Al2SiO5), and magnetite (Fe3O4) have gained global attention as a result of modern technological advances. In this regard, the mining and processing of these heavy minerals are a timely requirement to uplift the mineral industry and the economy of Sri Lanka. Therefore, the objective of this study is to investigate the geochemical variations of prospective heavy mineral deposits along the coastline in order to identify locations with economically significant concentrations of heavy minerals. Field excursions were carried out to identify the potential of heavy mineral placers in Sri Lanka. Sediment samples were collected from ten locations covering both the shoreline and raised beaches. X-ray fluorescence (XRF) analysis was used to determine the major and trace element compositions of sediments. When compared to average Upper Continental Crust (UCC) values, major and trace element variations show the enrichments of TiO2, Fe2O3, La, Ce, Zr, Cr, Nb, Th, and V. The abundance of TiO2, Fe2O3, and Zr, and visual examination of samples suggest the presence of higher concentrations of heavy minerals such as ilmenite, rutile, and zircon in the prospective locations. Moreover, the abundance of trace elements such as La, Ce, and Th implies the presence of rare earth elements (REEs) bearing heavy minerals such as monazite and zircon. In contrast, major elements (Al2O3, Na2O, and K2O) and large- ion lithophile elements (Ba and Rb) were significantly depleted compared to UCC values. Based on the XRF data and visual examination, it can be concluded that all the studied locations such as Verugal, Dickwella, Kosgoda, Payagala, Beruwala, Kalutara, Dharga Town, and Aruwakkalu can be identified as potential sites for heavy mineral placers. Finally, proper quantification is required to estimate economic grade and to determine mining feasibility. Keywords: Heavy minerals; Geochemical variation; Economic concentrations; Coastline of Sri Lanka
  • No Thumbnail Available
    Item
    Investigating the Potential of Clay Brick Waste to Be Used as a Raw Material for Rice Husk Ash-Based Bricks
    (Uva Wellassa University of Sri Lanka, 2021) Rajapaksha, R.P.T.N.; Wijerathne, W.D.C.C.
    Rice husk ash (RHA) and clay are well-known pozzolan materials that can be incorporated to tailor the properties of commercial bricks in the construction industry. Clay brick waste (CBW) is a clay product that is largely generated during mass-scale demolition activities. Although several works reported the use of RHA for developing bricks with improved physical properties, no work investigated how CBW influence the performance of RHA-based bricks. Accordingly, this work investigated how brick waste can be incorporated into RHA-based cement brick and how its properties such as compressive strength, water absorbency and morphology are influenced. For this, untreated RHA (particle size: 63-500 μm), CBW, OPC cement and water were used, and several bricks with dimensions 7×5×3 cm were developed by using different volume mixing ratios. The optimum mixing ratio among constituents was determined based on the brick’s porosity, surface finish and de-moulding capability. Results indicate that the optimum volume mixing ratio is 2:3:6:1 (cement: CBW: RHA: water). The RHA content should be less than 13% w/w to ensure de-moulding Having BCBW content of more than 44% w/w is acceptable for a better product, but too high contents around 64% w/w are not desirable as it discourages the removal of the brick for the mould. The brick with the optimum mixing ratio shows a water absorbance of 51% w/w and compressive strength of 3.61 MPa (28 days). Without RHA, the brick maintains the same compressive strength while reducing the water absorbance down to 20%. Compared to bricks reported in the literature using RHA/clay, RHA/lime/cement, RHA/aggregates, the proposed brick has significantly high water absorbency, and the compressive strength is around the reported values. Considering its properties, and the presence of heavy-metal-adsorptive RHA, the brick can be proposed for construction areas where wastewater channels are involved. Keywords: Rice husk ash; RHA; Clay brick waste; Compressive strength; Water absorbance; Optimum mixing ratio
  • No Thumbnail Available
    Item
    Shoreline Change Analysis along the East Coast of Sri Lanka: A Remote sensing- Based Approach
    (Uva Wellassa University of Sri Lanka, 2021) Weerasingha, W.A.D.B.; Ratnayake, A.S.
    The changes along the eastern coastlines of Sri Lanka have been investigated for short- and long-term natural and anthropogenic processes. Such coastal changes can be classified as either negative (coastal erosion, seawater intrusion) or positive (coastal accretion) impacts. The understanding of such impacts can directly be applied to coastal conservation/management and the designing of coastal engineering structures. In this study, the authors examined Landsat 5, 7, and 8 sun-synchronized earth resources satellite data for understanding coastal changes since 2000. These Landsat series have advanced sensors (e.g., thematic mapper (TM), enhanced thematic mapper plus (ETM+), operational land imager (OLI)) for data acquisition. Data selection, pre-processing, and processing were carried out using a geographic information system (GIS). Besides, the authors developed a new model known as “Jargon’s script” for data preprocessing and processing. Modified Normalized Difference Water Index (MNDWI) is the important algorithm of Jargon’s script models that helps to extract water and land features. The threshold value for the MNDWI to get maximum contrast of objects was identified as 0.13. Furthermore, the current study covered nearly 1043 km coastline along major coastal zones such as Jaffna, Mullaitivu-Trincomalee, Batticaloa-Hambantota, Matara, etc. Long- term and short-term coastal changes were then determined using Digital Shoreline Analysis System (DSAS) software linked to ArcMap 10.6. Results identified five major parameters such as net shoreline movement (NSM), shoreline change envelope (SCE), endpoint rate (EPR), linear regression rate (LRR), and weighted linear regression rate (WLR). In this study, coastal geomorphological changes were classified into eight classes based on the annual variation of EPR values, such as extreme erosion (>-10 m/year), high erosion (-10 to -5 m/year), moderate erosion (-5 m/y to -2.5 m/year), low erosion (-2.5 to 0 m/year), low accretion (0 to +2.5 m/year), moderate accretion (+2.5 to +5.0 m/year), high accretion (+5.0 m/y to +10 m/y), and extreme accretion (> +10 m/year). Those parameters can be used to visualize spatial and temporal variations of geomorphological changes along this coastline, and such variations can be used to correlate natural (monsoon, sea-level rising) and anthropogenic activities. According to the EPR results of Karainagar east, Kalido beach has the highest coastal erosion compared to other coastal areas. Keywords: Shoreline change rate; Satellite images; Coastal geomorphology; Sediment dynamics; East coast of Sri Lanka