Browsing by Author "Weerasooriya, R."

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    Characterization of Pyrite Particles by Molecular Modeling Methods.
    (Uva Wellassa University of Sri Lanka, 2010) Jayathilaka, H.A.P.P.B.; Gannoruwa, G.M.A.U.K.; Weerasooriya, R.
    Pyrite is the most abundant of metal sulfides in nature; Pyrite is often considered as an unwanted substrate in graphite industry. The quality of the nation's graphite resource is often degraded due to intimate association of this mineral. The data generated in this research will pave an initial step in suggesting an innovative of way of purifying graphite and adding a value for hither todate unwanted mineral pyrite. Pyrite showed great promise as a starting material for decontamination of water polluted with organic pollutants in both the presence and absence of light .It is an intrinsic semiconductor that exhibits both n- and p-type conductivity. The band gap is around 1 eV thus it can efficiently be used as a photo catalyst in the destruction of both organic and inorganic pollutants. Also an understanding of its reactivity is important for such applications as ore processing by flotation and solar energy conversion, as well as for geochemical processes like the production of acid mine waste waters. All of these processes involve reactions at pyrite surfaces and it is consequently important to understand the nature of these surface reactions. Pyrite surface chemistry plays an important role in many natural and technological systems, for example in extractive metallurgy, coal processing, geochemistry, acid-mine drainage and pollution control. Numerous studies on the nature of pyrite surface reactions have been conducted using various methods. The research is devoted to the development of theoretical cluster model for pyrite to mimic its properties in solid state. The data validation was made with IR spectroscopic data. For this pyrite clusters were developed with increasing complexity. The Gaussian 03 code was used to conduct calculations for geometry optimizations, frequency calculations and single point energy calculations using abinitio HF method. All clusters were successfully optimized at 3-21G level. The experimental IR data showed poor resemble with the calculations at 3-21G level. In order to validate the model calculations of pyrite clusters with 12, 22 and 84 atoms are currently in progress. Key words: Pyrite, HF method, Abinitio
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    Characterization of zero valent iron used for nitrate removal in drinking water
    (Uva Wellassa University of Sri Lanka, 2015) Shailaja, K.; Weerasooriya, R.
    Nitrogen is one of the important pollutants present in drinking water are runoff from fertilizer use; leaking from septic tanks, sewage; and erosion of natural deposits. When nitrate is absorbed in to blood hemoglobin is converted to methemoglobin. Methemoglobin does not carry oxygen efficiently. This results in reduced oxygen supply to vital tissues such as the brain. Severe methemoglobinemia (blue baby syndrome) can result in brain damage and death. In recent years, considerable efforts have been made to remove nitrate in water. The use of zero valent iron to remove nitrate from water represents one of the latest innovative methods in the reducing .process. The major reduction product was ammonia. Zero valent iron in contrast with iron powder have some advantages of specific surface area, high active surface, which lead to a increased denitrification rate of nitrate. Materials and Methods Surface titrations Surface titration was carried out as a function of the concentration of NaCl to determine pH zpc(Point of Zero net proton Charge).Prior to commencement of a titration 10.0g/l zero valent iron was NaNO3) strength. The initial pH value is around 10.0 after equilibration by adding 0.101 mol dm NaOH .Then, surface titration was started from pH 10.0 to 3.0 while bubbling with N2 gas to prevent any interference from atmospheric CO2. All titrations were carried out in thermostatic bath at 25.0 °C. At each titration point the data versus HCl) were measured by an auto titratior. A reverse base titration with 0.101 mol dm NaOH was performed to return the suspension to the original starting pH under same experimental conditions. This titration was repeated for three different ionic strength NaCl).However, only the acid titration data were considered for the analysis.These data unit for surface charge density was calculated.
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    Fabrication of Supersand for Water Purification
    (Uva Wellassa University of Sri Lanka, 2018) Thennakoon, R.S.; Weerasooriya, R.; Kumarasinghe, A.R.; Attanayake, A.N.B.; Ritigala, H.M.T.S.
    Fluoride is an essential constituent for both human and animal health that depends on concentration in the medium. The sand is conventionally used in water treatment plants to control water turbidity. This project is aimed at improving its performance using a chemical modification to remove other water contaminants as well. Thus improved substrate is designated as "Super sand". Super sand has proven to be a better adsorbent for the removal of certain heavy metals and dyes from water. Among several treatment technologies applied for fluoride removal, adsorption process has been explored widely and offers satisfactory results especially with mineral-based and/or surface modified adsorbents. Graphene Oxide was synthesized using the modified Hummer’s method. Super sand was synthesized by heating a mixture of sand and graphene oxide/deionized water in an oven for two hours. The process was repeated five times for multiple coating. Graphene oxide and super sand were characterized using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectrometry (EDS), Fourier Transform Infrared Spectroscopy (FT-IR) analysis and X-Ray Diffraction (XRD). The applicability of the synthesized material in the water industry for fluoride removal was studied utilizing sand, GO-sand and GO multiple coated sand at varying pH conditions. These results are to be confirmed by conducting further scientific studies.
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    Hardness Removal from Drinking Water Using Inorganic Ion Exchange Resin- Zeolite
    (Uva Wellassa University of Sri Lanka, 2019-02) Jayangani, K.C.; Weerasooriya, R.; Premachandra, N.P.; Jayarathna, I.P.L.
    The hardness of drinking water has become a major environmental problem at present and it has to be removed using cost effective technologies. This research focuses on using synthesized inorganic zeolite as an inorganic ion exchange resin for hardness removal. It is to be achieved by controlling the physical parameters on performance of zeolite in different hardness level of water. The research approach includes both batch and column experiments performed in laboratory condition to determine optimum level of zeolite on the removal process of Ca2+ and Mg2+ from water. A Batch contact time experiment was carried out with varying contact time for 10 g L-1 of a constant adsorbent mass at the concentration of 250 ppm for both Ca2+ and Mg2+. One hour was the optimum time. Accordingly, the experiment was carried out by varying adsorbent mass for different hardness level of Synthetic Hard Water (SHW). The different hardness level of water samples was reduced by 80-95% from 3-5 g dosage of zeolite. The data obtained from the batch adsorption system is not applicable for design a continuous adsorption system. Then, column sorption studies were carried out using fixed bed column, which was filled with sand and zeolite, mixed in 1:1. The influent flow rate and concentration of the SHW solution were kept constant at 12.7 mL min-1 and 100 ppm, respectively. The column was reached exhaustion after the 30 min, according to the breakthrough curve for the column. According to results, it can be concluded that synthetic inorganic zeolite can be used to remove hardness from all the hardness range of moderately hard water, hard water and very hard water in high percentage (80-95%).
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    Hardness Removal Using Graphite-based Nano Materials
    (Uva Wellassa University of Sri Lanka, 2018) Kularathne, K.A.M.; Weerasooriya, R.; Kumarasinghe, A.R.; Attanayake, A.N.B.
    Water hardness creates substantial issues both in health sector and in industry. In regulatory agencies hardness in drinking water is often categorized as a secondary contaminant in that its regulation is not mandatory. However, high hard waters are not palatable. The hardness in the water is defined as the presence of di- and trivalent cations. However the removal of hardness from water is no easy task. Ion exchange resins were commonly used to control drinking water hardness which creates reject water enriched with monovalent cations. The methods based on sorption offers several advantages as such they are economical and do not require high technology. Further most of the adsorbents are readily available. The major limitation of the method is its efficiency. This project aimed at determining developing substrate to remove divalent cations from drinking water using nano Grapheneoxide (GO). GO was synthesized from natural vein graphite of Sri Lanka. Grapheneoxide (GO) was synthesized using the modified Hummer's method. Results showed that the suitable pH for calcium removal was pH 10 but there is a Calcium removal below pH 8 (pH 5.5 to 7) and the optimal concentration was 50 ppm. Equilibrium isotherms have been analyzed using Langmuir and Freundlich isotherm models. The adsorption data were fitted well in Langmuir isotherm than Freundlich isotherm for GO. GO was characterized using Scanning Electron Microscope (SEM),Energy Dispersive X-ray Spectrometry (EDS), Fourier Transform Infrared Spectroscopy (FT-IR) analysis and X-ray Diffraction (XRD) and the results were in good agreement with the literature. Calcium adsorption isotherms were also prepared to assess its applicability for water industry.
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    Kinetics Modelling of Partial Degradation of Carbofuran by Pyriye
    (Uva Wellassa University of Sri Lanka, 2011) Dhanasekara, S.A.K.M.; Walewela, N.; Jayarathna, L.; Nanyakkara, K.G.N.; Weerasooriya, R.
    Fenton Process is initiated by the formation of hydroxyl radical in accordance with the classical Fenton's reaction: Fe2+00 + H2024 OH + Fe3+0,4) If the product Fe" is reduced, the Fe2+ is regenerated for the next Fenton cycle; hence, Fe34 acts as an auto-catalyst. This reaction is also known to occur when Fe2+ is present in solid phase (Cohn et al., 2006; Kwan and Volker; 2003; Watts et al., 2003). The slow conversion of H202 -9 OH when magnetite, iron hydroxides, or pyrite are present is ascribed to a Fenton like mechanism (Cohn et al., 2006). In nature pyrite is the most abundant of metal sulfides. In Sri Lanka pyrite is an unwanted substrate in graphite industry. It is intimately associated with graphite by degrading the quality of the nation's graphite resource and it is confirmed that pyrite can be used as a starting material for purification of the water polluted with organic pollutants in both the presence and absence of light (Weerasooriya et al., 2006). When properly fabricated, pyrite based OH generation technology will hold a great promise in water treatment industry due to its simplicity, cost-effectiveness, and environmentally friendliness. Carbofuran (2,2-dimethy1-2,3-dihydro- I -benzofuran-7-y1 methylcarbamate) is a broad spectrum carbamate pesticide. Because of high water solubility of carbofuran (320 mg/liter at 25 °C) the risk of ingestion in to the human body is high Kidd and James (1991). Carbofuran, was selected for the present study with the aim of investigating its degradation in pyrite mediated aqueous environments under anaerobic conditions due to its wide use as an insecticide and nematicide in agricultural applications and high toxicity (Bachman et al., 1999).
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    Phytoremediation Potential of Indian Mustard (Brassica Juncea) genotypes for Cr (Vi) Mitigation
    (Uva Wellassa University of Sri Lanka, 2011) Wijethunga, W.M.K.T.; Wijesekara, K.B.; Weerasooriya, R.
    Note: See the PDF Version Phytoremediation is a low cost, environment friendly technology of using plants to mitigate hazardous contaminants front the environment (Diislicnkov e/ ml., 1997), Phytoremediation efficiency of selected nine accessions of Indian mustard (Brassica juncea) was examined at different experimental conditions, in vitro and in vivo. Phytoremediation ability of Indian mustard (Brassica juncea) is well established, thus a good candidate plant for Phytoremediation. (Weerakoon and Soniaratne, 2009), This investigation demonstrates Phytoremediation potential of Brassica juncea genotypes for Cr(VI) i mitigation.
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    Removal of Arsenic (V) in Water using Humic Acid-Modified Meetiyagoda Kaolinite
    (Uva Wellassa University of Sri Lanka, 2013) Jayahansani, K.H.D.; Udagedra, D.T.; Weerasooriya, R.
    Kaolinite is one of the major clay types which can be used to remove ions from the water by using its adsorption capacity (Krishna and Gupta, 2006). Though several clay types are found in Sri Lanka, significant use of them for value addition purposes is not practiced.By considering that fact and the unique ability of kaolinite to remove ions from water is targeted throughout this research.Meetiyagoda kaolinite is used as clay type, because it is currently used only as a raw material for ceramic industry and none of the researches have been conducted to investigate its ability to remove ions from water. Therefore the ultimate goal of this study is to fill that gap and develop a value added product from Meetiyagodakaolonite. This research focuses on removing arsenic (V) from water while modifying kaolinite surface using Humic Acid in order to enhance its adsorption capacity and measuring the removal amount of arsenic (V) by changing amount of clay, concentration of arsenic (V) and pH. Methodology The purified Meetiyagoda kaolinite sample was taken from Meetiyagoda clay refinery and it was dried, ground and sieved to obtain 75µmparticle size.This particle size was preferred because, when particle size gets smallest it increases the surface area of kaolinite which results in more adsorption of arsenic on to kaolinite surface. Humic acid was prepared by mixing dried homo-ionized clay was prepared using kaolinite and 1M CaCl2.Previously prepared humic acid was readjusted to homo-ionized clay was added to pH neutral humic acid and the humic acid-clay suspension was incubated in mechanical shaker, then the suspension was centrifuged. Finally the humic acid coated clay sample was dried and used. The effect of arsenic removal by humic acid modified Meetiyagoda kaolinite was analysed while changing amount of humic acid modified clay, initial arsenic concentration and pH of the solution using Varian 700ES ICP-OES Atomic Absorption Spcetrophotometer.
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    Synthesis and Characterization of Iron Pyrite Nano Particles for Pollution Control
    (Uva Wellassa University of Sri Lanka, 2010) Siriwardana, B.V.D.T.; Gannoruwa, G.M.A.U.K.; Weerasooriya, R.
    Pyrite, FeS2 commonly referred as fool's gold is the most abundant sulfide phase in the earth surface region. The reactivity of pyrite is of central importance in a devastating environmental issue known as acid mine drainage, and in beneficial commercial processes such as mineral benefaction. Pyrite is an unwanted entity in nation's graphite which depredates the value of the mineral repository. The overall aims of this project were two-fold: in one way purification of the graphite by removing pyrite will be suggested probing it's surface properties. Once it is separated, the value of this unwanted pyrite will be added by enhancing water splitting to generate OH' radical for none selective destruction of organic pollutants in water. In this work, in order to examine the surface properties pyrite samples were synthesized at laboratory scale using FeSO4.7H20, NaHS and elemental S as starting materials. The corresponding interactions of Fe (II) with freshly polysulphide were examined at 25°C over the pH range 5.5 to 8. Attempts were made to achieve pure pyrite phase through a simple chemical reaction in the liquid state followed by annealing. The phase purity and the structure were determined using FTIR spectrometry. Surface titrations were done for three different ionic strengths to determine zero point charge value of pH. The XRD and TEM analyses are currently in progress. Key Words: Iron Pyrite, FTIR Spectroscopy, Surface Titrations
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    X-ray Photoelectron Spectroscopic Probing of Nano-zero Valent Iron Assisted Nitrate Degradation
    (Uva Wellassa University of Sri Lanka, 2021) Halpegama, J.U.; Heenkenda, K.Y.; Kuss, C.; Nanayakkara, K.G.N.; Herath, A.C.; Rajapakse, R.M.G.; Weerasooriya, R.
    Excess nitrate adversely contributes to groundwater pollution. However, nitrate remediation is not an easy task. Upon boiling it concentrates, and does not sorb, in significant amounts, onto soils or other surfaces. Metallic iron (Fe) is an attractive alternative for nitrate reduction compared to conventional treatment processes. In this research nano zero valent iron-reduced graphene oxide composite (nZVI-rGO) was synthesized using modified Hummers method. Polyphenols derived from natural tea leaves were used to reduce Fe2+/Fe3+ into Fe. All X-ray photoelectron spectroscopic (XPS) measurements were carried out by an XPS (5000 VersaProbe II ULVAC-PHI Inc., Japan) system equipped with an X-ray source (monochromatic Al K𝛼 1486.7 eV X rays). These measurements were used to elucidate the surface sites and the oxidation states of nitrogen adhered to the surface of nZVI-rGO. At 5.6 pH, composite material reduce 70% of 0.8064 mM nitrates within an hour at 25 . However, the mechanistic steps of nitrate reduction are inconclusive to date. The Fe-XPS signal was assigned to oxidized Fe signaling surface oxidation, and Fe(0) within the core-shell structure of nZVI-rGO. The N 1s transition indicates the aromatic N presence in polyphenols. After nitrate reduction, ammonia accounts for 95% of the nitrogen mass balance with N2, NO and NO2- traces. The peak at 706.7 eV contributes to Fe(0) was disappeared and the intensity of the Fe(II) and Fe(III) peaks decreased. During the reduction, oxidized Fe2+(aq) was converted into Fe3O4 via spontaneous electron transfer between the Fe2+ and the pre-existing surface Fe3+ oxides and enhanced the nitrate removal efficiencies. nZVI reduces nitrate into NO, which has a high electron density. This NO can easily trap free electrons and form negatively charged NO-. The adsorbed NO- to the cationic iron oxides sites of nZVI-rGO surface identified by N 1s transition peak at 401.7 eV. Further research is required for the identification of nitrogen- containing groups of natural green tea leaves polyphenols to confirm the surface sites of nitrogen. Keywords: Nano-zero valent iron; Nitrate reduction; Polyphenols; Reduced graphene oxide; X-ray photoelectron spectroscopy