Adsorption and decomposition of triclosan by activated carbons, manganese oxides, and their composite materials from aqueous solution
Files
(Published version)
Date
2010
Authors
Fang, Sheng
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
thesis
Citation
Statement of Responsibility
Conference Name
Abstract
This research investigates the use of activated carbon (AC) and manganese oxides as adsorbents and oxidizing agents to adsorb and oxidize triclosan, a compound which is widely used in pharmaceutical and personal care products and it is frequently detected in the environments. The main object is to conduct a systematic investigation for developing a fundamental understanding of interface reactions between triclosan and the surfaces of activated carbon and manganese oxides.To systematically evaluate the adsorption behaviour of triclosan on AC, three commercially available ACs, P1300, Picazine HP and Hydrodarco C, were modified by various technologies, such as oxidation by nitric acid, thermal treatment in nitrogen gas and amination. Oxygen content affects triclosan adsorption by localized hydrophilic sites for water binding, requiring the displacement of adsorbed water by triclosan, provided the pore width can accommodate both molecules. The introduction of nitrogen functional groups increases surface basicity, resulting in increased adsorption capacity. Pores 1-2 nm in width show the most efficient triclosan adsorption. Langmuir and Freundlich equations can adequately describe the adsorption isotherms while adsorption kinetics fit pseudo first or second order kinetics equations depending on the materials' properties.Oxidation of triclosan was investigated by the degradation of triclosan on one commercially available and four synthesized manganese oxides. At pH approaching neutral condition, four of the manganese oxides, including the commercially available oxide showed modest or no reaction with triclosan. Only the synthesized manganese oxide with most poorly crystalline structure showed high oxidative potential. Triclosan transformation by all manganese oxides exhibited strong increases in reaction as the pH was decreased. The overall order for each initial rate is a function of the oxide type used as catalyst and solution pH.Triclosan adsorption and its decomposition were investigated for the combined catalyst system of manganese oxides supported on a surface of Picazine HP. Well dispersed manganese compounds can be distributed on the surface and internal pores. The introduction of manganese compounds onto the AC surface reduced triclosan uptake to less than that of original carbon, Picazine HP. This is due to loss of specific surface area and pore volumes. The increase in adsorption capacity at lower pH is due to the activity of manganese oxides. The isotherms of triclosan adsorption by synthesized materials are also adequately described by two classical isotherm models, i.e. Langmuir and Freundlich equations.Overall, triclosan can be effectively removed by adsorption on AC. The adsorption is strongly affected by the surface chemistry and physical properties. Micropores, oxygen and nitrogen functional groups govern triclosan adsorption capacity and kinetics. The adsorption and oxidation of triclosan on manganese oxide surfaces is determined by the crystal structures of the manganese oxides and the solution pH. The introduction of manganese oxides on AC, generally, decreases the adsorption capacity because of loss of pore volume. The activity of manganese oxides on the AC surface is pH dependent.
School/Discipline
University of South Australia School of Pharmacy and Medical Sciences.
School of Pharmacy and Medical Sciences.
School of Pharmacy and Medical Sciences.
Dissertation Note
Thesis (PhD(Applied Science))--University of South Australia, 2010.
Provenance
Copyright 2010 Shengfu Fang
Description
EN-AUS
Access Status
506 0#$fstar $2Unrestricted online access