NANOCOMPOSITE APPLICATION FOR SELENIUM REMOVAL – PARAMETRIC STUDIES AND KINETIC MODELING

Nano composite material was synthesized using calcium hydroxy apatite and Phoenix Dactlyifera tree powder using wet chemical precipitation method and characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The influence of operating parameters namely initial pH (3 -11), selenium concentration (50 -200 mg L-1 ), nanocomposite dose (0.5 - 6.0 g L-1 ), presence of competitor chloride ion (0 -10 g L-1 ) and agitation speed (0 – 600 rpm) on the metal uptake was studied. A correlation relating nano composite dose and selenium uptake was proposed as selenium uptake = 202.3 (e-0.259* nanocomposite dose) he maximum uptake capacity of the nanocomposite was found to be 57.27 mg g-1 under optimal environmental conditions with an initial selenium concentration of 100 mg L-1 . Monolayer sorption mechanism, proposed by Langmuir isotherm, was found to apply for this process and the isotherm constants were determined. Modified Ritchie second order and pseudo second order models were fitted to the experimental data and pseudo second order model correlated well with rate constant of 1.5 x 10-3 g mg-1 min-1 and maximum uptake capacity of 70.92 mg g-1 at 32 °C with 100 mg L-1 initial metal concentration. Ritchie model rate constant was evaluated as 1.41×10-2 min-1 under similar process conditions

Chapter 6 Transport and Accumulation of Stable Metals and Radionuclides in Dulas Bay, North Wales

Dulas Bay in Anglesey, North Wales, is an area of scientific interest not only because it receives radioactive contaminants from Sellafield, but also it receives high concentrations of contaminant metals from the abandoned Parys Mountain mine via the Afon Goch. This system, therefore, provides an ideal case study to investigate the transport and the accumulation of radionuclides and stable metals and any connections between them. Samples were collected and U and Pu were separated prior to electrodeposition and alpha spectrometry. ICP-MS, XRF and gamma spectrometry were also carried out.</jats:p

Mercury meniscus on solid silver amalgam electrode as a sensitive electrochemical sensor for tetrachlorvinphos

The in-house prepared mercury meniscus modified solid silver amalgam electrode (m-AgSAE) was successfully applied for the detection of organophosphate pesticide tetrachlorvinphos in pH 7 buffer solution. The electrochemical performance of m-AgSAE for the reduction of tetrachlorvinphos was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV), respectively. The surface morphology of solid silver electrode (AgE), as-amalgamated solid silver amalgam electrode (AgSAE), and polished solid silver amalgam electrode (p-AgSAE) was examined by field emission scanning electron microscopy (FESEM). Among the applied techniques, DPV and SWV analysis showed a remarkable increase in the reduction peak current and provided a simple, fast, and sensitive method for the determination of tetrachlorvinphos. The electrochemical impedance spectroscopy (EIS) was used to correlate the electrocatalytic activity of AgSAE, p-AgSAE and m-AgSAE with their interfacial charge transport capabilities. Under the optimized experimental conditions, the DPV and SWV responses were linear over the 1–9 μM and 10–50 μM concentration ranges with a detection limit of 0.06 μM for DPV and 0.04 for SWV. The estimation of tetrachlorvinphos in the ground and waste water samples with the proposed method was in good agreement with that of the added amount. The proposed electrochemical method not only extends the application of non-toxic m-AgSAE, but also offers new possibilities for fast and sensitive analysis of tetrachlorvinphos and its structural analogs in environmental samples. Keywords: Organophosphate pesticide, Tetrachlorvinphos, Electrochemical sensor, Mercury meniscus modified solid silver amalgam electrode, Electrocatalytic reductio