Browsing by Author "Nanayakkara, K.G.N."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Development of Graphite/Ir Anode for Electro-chemical Denitrification of Landfill Leachate
    (Uva Wellassa University of Sri Lanka, 2016) Sivasubramaniyam, U.; Manipura, A.; Nanayakkara, K.G.N.
    Contamination of water by NO3 can cause health issues such as methernoglobinemia or blue baby syndrome. Previous studies revealed that high concentration of inorganic nitrogen compounds such as NO3 and numerous organic nitrogen compounds present in leachate. Thus, appropriate treatment of landfill leachate is urgently required. Electro¬chemical denitrification is one of the best technologies which can be used in denitrification. In this research, anode was developed by applying iridium (Ir) coating onto the graphite substrate by electro and electro-less plating methods. In electro-less plating, glycerol or formaldehyde was used as reducing agent while 325 ppm It' standard solution was used as the Ir precursor. EDTA was used as complexing agent. In electroplating, Ir was deposited onto well cleaned graphite cathode at 0.3 V and 110 mA from 250 ppm Ir3+ standard solution coating bath. The success of the plating process was initially analyzed using UV-Visible absorbance spectrum studies. UV-Vis spectrums and color changes of plating baths were shown that the Ira" concentrations in the plating bath were reduced with time for all methods. According to UV-Vis spectrums, excess formaldehyde which was used as reducing agent resulted high efficiency of plating. Therefore graphite/Ir anode which used excess formaldehyde in the plating bath was examined for Scanning Electron Micrograph (SEM), Energy Dispersive X-ray spectroscopy (EDX) and denitrification process. Observation of very small sizes of grains and 12.44 % Ir element present in the anode surface were the evidences that Ir deposited onto graphite substrate. Finally, developed anode and commercially available cathode electrodes were used for removing nitrate from nitrate solution. Keywords: Denitrification, Landfill leachate, Iridium, Graphite
  • No Thumbnail Available
    Item
    Investigating Properties of Rice Husk for Contaminant Removal from Polluted Water
    (Uva Wellassa University of Sri Lanka, 2011) De Silva, T.D.K.; Nanayakkara, K.G.N.
    Note: See the PDF Version Contamination of ground and surface water by different pollutants is a major environmental problem. These pollutants are discharged by sources such as industries into natural water streams. Water pollutants are toxic to most aquatic organisms, human body and may cause denaturing of protein, tissue erosion, and paralysis of the central nervous system and also damage the kidneys, liver and pancreas. Most of the pollutants are toxic even at very low concentrations. Therefore, designing effective strategies to remove pollutants from water is of practical interest (Zhang et al., 2011). Utilization of one waste material to control pollution caused by another is of high significance in the remediation of environmental problems. Rice husk is an abundantly available agricultural waste. The compositions of rice husk are 32% cellulose, 21% hemicellulose, 22% lignin and 15% mineral ash (Nakbanpote et al., 2007). Rice husks can be used as a low cost adsorbent (Tarley and Arruda, 2004). This research aimed to chemically modifying surface properties of rice husk to be used in waste water treatment. It would help to increase the volume of purified consumable water.
  • Thumbnail Image
    Item
    Surface Modification of Activated Carbon to Treat Polluted Water Streams
    (Uva Wellassa University of Sri Lanka, 2011) Pathiraja, G.C.; Nanayakkara, K.G.N.
    NOTE: see the PDF version Water pollution due to the industrial applications, agro chemicals, etc. is a serious environmental problem which creates health, economical, and ecological impacts worldwide. The presence of toxic compounds, both organic and inorganic, in water streams creates significant threats to man and nature. Therefore, polluted water streams should be purified before releasing to the environment (Akhtar et al., 2006); (Massa et al., 2004). Adsorption is one of the most versatile and effective method, among other different methods. Adsorption is a natural process by which molecules of a dissolved compound collect on and adhere to the surface of an adsorbent solid. Activated carbon has a great potential for effectively removing contaminants from water by adsorption process due to its electrochemical surface properties. Most forms of activated carbon are non-polar in nature, so they have the greatest affinity for other non-polar substances. As a result, they are most effective in the removal of a variety of organic contaminants. However, activated carbons do not effectively remove trace metals, contaminants of high solubility or inorganic salts like nitrates. Hence, modifying the surface chemistry of activated carbon becomes an attractive route towards novel applications in enhancing the efficiency in water treatment (Chen et al., 2003). In this research, chemical treatment was used to modify the commercially available activated carbon and the modified material was characterized.
  • No Thumbnail Available
    Item
    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