Development of Nanomaterials and Technologies for Environmental Applications

Authors

Homer Genuino, University of Connecticut - StorrsFollow

Date of Completion

10-8-2013

Embargo Period

10-8-2014

Keywords

nanomaterials, nanotechnology, manganese oxides, titanium dioxide, photocatalysis

Major Advisor

Steven L. Suib

Associate Advisor

Nicholas E. Leadbeater

Associate Advisor

Alfredo Angeles-Boza

Associate Advisor

Amy R. Howell

Associate Advisor

Edward J. Neth

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Campus Access

Abstract

This research work focused on the preparation of manganese oxide-based nanomaterials using a simple reflux method, characterization, and various applications including laboratory-scale development of emulsion and microwave (MW) photocatalysis technologies. This dissertation consists of five major sections.

Chapter 2 describes the enhancement of the photodegradation of toxic N-Nitrosodimethylamine (NDMA) in water using amorphous manganese oxide (AMO) and crystalline platinum manganese oxide catalysts. Results from spectroscopic, chromatographic, and voltammetric studies were interpreted to study the role of the catalysts and the reactive oxygen species that form, and the kinetics and mechanism of catalyzed NDMA photodegradation. Mixed valencies of Mn and the presence of physisorbed oxygen, which reacts with photogenerated electrons to form reactive oxygen species, played significant roles in the enhancement of the photodegradation of NDMA.

Chapter 3 presents the investigation of the effects of visible and UV light on the characteristics and properties of Prudhoe Bay and South Louisiana emulsions to better understand the role of sunlight on the fate of spilled crude oils that form emulsions with a dispersant in the aquatic environment. The unique changes in emulsion properties were attributed to direct photodegradation and photooxidation of crude oil components.

Chapter 4 describes the development of a novel continuous-flow reactor to investigate the synergetic effects of UV and MW radiation on TiO₂ nanoparticles for the enhancement of photodegradation of Direct Red-81 and Bromothymol Blue dyes. The efficiency of the combined UV and MW radiation was higher than the sum of the isolated and corresponding thermal effects and directly proportional to the MW power and dissolved oxygen concentration. Accelerated rates of dye degradation on incorporation of MW were attributed to the generation of more hydroxyl and superoxide anion radicals and an increase in hydrophobicity of TiO₂.

Chapter 5 describes the synthesis of cryptomelane-type octahedral molecular sieve manganese oxide (K-OMS-2), AMO, and mixed copper manganese oxide nanomaterials and, together with commercial MnO₂, their characterization by various techniques. This group of catalysts was investigated for gas-phase total oxidation of six volatile organic compounds under air atmosphere. The higher oxidative activities exhibited by the catalysts were attributed to a combination of factors including structure, morphology, hydrophobicity, and redox properties. The mobility and reactivity of active oxygen species were strongly correlated with catalytic activities.

Chapter 6 demonstrates the use of high-valent vanadium ion substituted into K-OMS-2 framework at different concentrations (0-20%) for total and preferential catalytic oxidation of CO. Substitutional doping resulted in materials with modified composition, morphology, thermal stability, and textural, redox, and catalytic properties. The mobility and lability of surface oxygen, formation of hydroxyl groups, and enhanced surface redox properties promoted by V doping, were strongly correlated with the enhancement of catalytic activities of K-OMS-2 nanomaterials.

Recommended Citation

Genuino, Homer, "Development of Nanomaterials and Technologies for Environmental Applications" (2013). Doctoral Dissertations. 233.
https://digitalcommons.lib.uconn.edu/dissertations/233