Thesis (Ph. D.)--University of New South Wales, 2003. / "A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy, School of Chemical Engineering and Industrial Chemistry, University of New South Wales, July 2003" Includes bibliographical references. Also available online.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains x, 60 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 52-59).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 110-119). Also available via the Internet.

Thesis (Ph. D.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains ix, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.

Graduation date: 1994

<p>This thesis is based upon synthesis and structure determination of new transition metal oxo-halide compounds, which includes p-element cations that have a stereochemically active lone pair. A synthesis concept has been developed, which uses several different structural features to increase the possibility to yield a low-dimensional arrangement of transition metal cations. A total of 17 new compounds has been synthesised and their structures have been determined <i>via</i> single-crystal X-ray diffraction. The halides and the stereochemically active lone-pairs will typically act as terminating species segregating into regions of non-bonding volumes, which may take the form of 2D layers, 1D channels or Euclidean spheres. The transition metals that have been used for this work are copper, cobalt and iron. The Hard-Soft-Acid-Base principle has been utilized to match strong Lewis acids to strong Lewis bases and weak acids to weak bases. All compounds show tendencies towards low-dimensionality; they all have sheets of transition metal cations arranged into layers, where the layers most often are connected via weak dispersion forces.</p>

This thesis is based upon synthesis and structure determination of new transition metal oxo-halide compounds, which includes p-element cations that have a stereochemically active lone pair. A synthesis concept has been developed, which uses several different structural features to increase the possibility to yield a low-dimensional arrangement of transition metal cations. A total of 17 new compounds has been synthesised and their structures have been determined via single-crystal X-ray diffraction. The halides and the stereochemically active lone-pairs will typically act as terminating species segregating into regions of non-bonding volumes, which may take the form of 2D layers, 1D channels or Euclidean spheres. The transition metals that have been used for this work are copper, cobalt and iron. The Hard-Soft-Acid-Base principle has been utilized to match strong Lewis acids to strong Lewis bases and weak acids to weak bases. All compounds show tendencies towards low-dimensionality; they all have sheets of transition metal cations arranged into layers, where the layers most often are connected via weak dispersion forces.