Publication Date

2013

Document Type

Dissertation

Committee Members

Rachel Aga (Committee Member), Joseph Caruso (Committee Member), Songlin Cheng (Committee Member), Suzanne Lunsford (Advisor), Doyle Watts (Committee Member)

Degree Name

Doctor of Philosophy (PhD)

Abstract

Heavy metals, particularly Lead (Pb) and Cadmium (Cd), had been long identified as hazardous pollutants in the environment. Joining the continuous effort to alleviate this dilemma, a new electro-chemical sensor has been developed to assess the level of Pb and Cd in aqueous environment. The current work describes the utilization of two different electro-analytical techniques, cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV), in conjunction with the novel Titanium Dioxide/ Zirconium Dioxide/ Tween 80 (TiO2/ ZrO2/ Tween 80) carbon paste composite electrode to qualitatively and quantitatively analyze Pb and Cd. In this dissertation, along with a comprehensive literature review of recent electro-chemical sensors developed to quantify heavy metals, theoretical background overview of the different analytical and spectroscopic techniques employed in this study is also provided. With respect to cyclic voltammetric analysis, CV is used to optimization of electrode synthesis conditions, estimate the TiO2/ ZrO2/ Tween 80 carbon paste composite electrode active surface area, optimize the working pH, and calculate two kinetic parameters, electron transfer coefficient and heterogeneous electron transfer rate constant, for the oxidation- reduction process of Pb and Cd at the electrode surface. Furthermore, quantitative analysis of Pb and Cd via cyclic voltammetry is also carried out. In addition, square wave anodic stripping voltammetric analysis of Pb and Cd was conducted at part per billion concentration range for both metals. For this analysis, Pb and Cd are quantitatively measured, both individually and simultaneously. Moreover, the effects of environmental interferences on the performance of the electrode is also investigated via SWASV using two modeling surface active substances and six common di-valence metals. Asides from quantitative analysis in modeling solution, SWASV analysis of Pb and Cd is also carried out in two different river waters and one well water sample, with inductively coupled plasma optical emission spectroscopy (ICP-OES) being employed as verification method. Successful detection of Pb and Cd in real water samples illustrates the potential of the newly developed electrode for real world applications. And lastly, scanning electron microscopy and X-ray photoelectron spectroscopy are utilized to investigate the morphology and chemical characteristics of the electrode surface to better understand the logic behind the electro-chemical reaction between the analytes and electrode surface. The ultimate goal of the project is to create a novel sensor that not only possesses favorable electrochemical characteristics (electro-chemical stability, selectivity, and enhanced electro-catalytic activity) to quantify Pb and Cd at trace levels, but also suitable for mass commercial production (easy to produce at marginal unit cost).

Page Count

173

Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded

2013

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