The effect of free chlorine and monochloramine on lead in drinking water and epitaxial electrodeposition of tin sulfide

Electrochemical deposition is utilized in various electronic and photovoltaic applications and in the protective coating industries. This dissertation primarily addresses the environmental aspects of electrochemical deposition. In the first part of this study, Pb dissolution in drinking water was investigated in the presence of two disinfectants: free chlorine (in the form of HOCI/OCr) and monochloramine (NH₂Cl). In the second part of this study, epitaxial SnS nanodisks were electrodeposited onto a Au(100) substrate. Water utility systems use either free chlorine or monochloramine in their disinfection program. Whereas free chlorine reacts with natural organic matter in the water to produce halogenated organic byproducts that are suspected to be carcinogens, NH₂Cl, a weaker oxidant, may lead to elevated Pb levels in drinking water. Thermodynamically, NH₂Cl is capable of oxidizing Pb and Pb²⁺ species to PbO₂, which is a stable and insoluble oxide of Pb and should minimize the Pb dissolution. However, experimental results utilizing EQCM, XRD, and SEM show that NH₂Cl elevated Pb levels in water by oxidizing Pb or reducing PbO₂ films to soluble Pb²⁺ species. The solubility of PbO₂ in NH₂Cl increases if the concentration of NH₂Cl increases or the pH of the water decreases from pH 10 to pH 7. Epitaxial films of Δ-SnS were deposited electrochemically on single-crystal Au(100) surfaces from an acidic solution at 70°C. The films grew with [100] and [301] out-of-plane orientations and four equivalent in-plane orientations. For the SnS(100) orientation, the in-plane mismatch was 2.4% in the [010] direction and 6.1% in the [001] direction. For the (301) orientation, the in-plane mismatch was 2.4% in the [010] direction and 3.4% in the [103] direction. SEM images of the deposit show a disk-like morphology with a diameter of 300 nm and a thickness of 50 nm --Abstract, page iv