Browsing by Author "Mathota Arachchige, Y.L.N."

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Correlation of Ligand Donicity with Catalytic Activity in a Series of Gold (I) Carbene and Phosphine Complexes
(Staff Development Center, University of Kelaniya, 2015) Mathota Arachchige, Y.L.N.; Slaughter, L.M.
Catalytic activities of transition metal complexes are influenced by both steric and electronic effects arising from ancillary ligands. In the case of linear gold (I) complexes, the available evidence suggests that ligand electronic effects are more important. However, available methods to investigate the donor abilities of ligands are not easily conducted with gold (I) complexes. In this study, the donor abilities of selected carbene ligands, including N-heterocyclic carbenes (NHCs), abnormal N-heterocyclic carbenes (aNHCs), and acyclic diaminocarbenes (ADCs), as well as phosphine ligands, at a gold (I) center were studied. Methyl isocyanide adducts and 1,3- diisopropylbenzimidazolin-2-ylidene (i Pr2-bimy) adducts of a series of gold complexes were synthesized as IR probes and 13C NMR probes, respectively. The gold-catalyzed intramolecular cyclization of alkynes, which is known to be accelerated by strong donor ligands, showed an inverse relationship between the Δν of the MeNC IR probe and the reaction rate. The same trend was observed with the 13C NMR probe, but the MeNC IR probes gave a better correlation with catalytic rates. Explanations of the observed donicity trends in terms of bonding effects will be discussed.
Removal of diazinon pesticide from water using a polyacrylamide - Strychnos potatorum (Ingini) seeds derived activated carbon composite
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Amarathunga, N.V.; Mathota Arachchige, Y.L.N.
Water is one of the essential resources on earth and it is very important to protect water for the survival of all living beings. Modern agricultural activities are highly chemically intensive and can be considered as one of the major polluters of drinking water. Therefore, removing pesticide contaminants from water sources that are used in agriculture is an essential requirement. Among pesticides, diazinon has been identified as one of the major organophosphorous pesticides (OPPs) which are used in Sri Lankan agricultural fields. However, pesticide removal from water by means of low cost and efficient technologies is still a major challenge. In this study, a novel adsorbent material was synthesized using polyacrylamide (PAM) and activated carbon (AC) from Strychnos potatorum seeds. Polyacrylamide-activated carbon composite (PAAC) were successfully prepared through aqueous solution polymerization. The synthesized PAAC composite was characterized by FTIR and SEM. The adsorption of aqueous pesticide samples on PAAC composite was studied. High Performance Liquid Chromatography (HPLC) technique was used to determine the diazinon concentration in the medium. Batch adsorption experiments were conducted by varying contact time, initial diazinon concentration and adsorbent dosage at pH 5 and at 25oC. Adsorption isotherm and kinetics studies were also performed. Batch adsorption results showed that the optimized parameters for the adsorption of diazinon onto PAAC sample were contact time of 60 min, initial concentration of 10 mg/L and adsorbent dosage of 0.25 g. Under these optimized conditions, diazinon reduction percentage of 62% and maximum adsorption capacity (qmax) of 1.48 mg/g were achieved for diazinon at pH 5 and at 25 oC. The obtained results are satisfactory since diazinon is present in water in mild concentrations. Adsorption data were found well behaved with the Freundlich adsorption isotherm. Therefore, adsorption on a heterogeneous surface can be predicted. Diazinon adsorption has shown pseudo first order kinetics. Based on the results observed, it can be concluded that the novel adsorbent material could be used as an economical and highly efficient adsorbent for diazinon removal from water.