Use this URL to cite or link to this record in EThOS:
Title: Mesoporous TiO2/Fe2O3 bicomposites : synthesis and mechanistic studies of arsenic scavenging
Author: Lapinee, Chaipat
ISNI:       0000 0004 6496 1812
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
Availability of Full Text:
Access from EThOS:
Access from Institution:
Many parts of the world have arsenic contamination problems in drinking and ground water. The high toxicity of arsenic threatens people’s health, since exposure to it can cause cancer and other dangerous diseases. Inorganic arsenic in natural water is found in two oxidation states, AsV(arsenate) or AsIII(arsenite). AsIII has the highest toxicity comparing with AsV and difficult to remove due to zero charge species of AsIII at pH below 9. Consequently, photocatalytic oxidation of arsenite is a key challenge to improve removal efficiencies of future sorbents. Recent work has suggested that a TiO2/Fe2O3 binary mixed oxides could play a key role in the design of future sorbents as it combines photocatalytic oxidation and adsorptive properties alike. The aim of this thesis presented was to characterise the interaction of arsenic with TiO2/Fe2O3 binary mixed oxides synthesised using different methods and to critically evaluate the potential of these bicomposites for future development work. To this end, three different synthetic methods with respect to cost, time and energy consumption during production were tested. The mechanisms of arsenic interaction were assessed using macroscopic (i.e. adsorption isotherms, adsorption kinetics) and microscopic (i.e. synchrotron techniques) studies and the photocatalytic oxidation was studied using synchrotron and UV irradiation. An electrochemical method for detection of arsenic has been implemented for the accurate analytical determination of AsIII and AsV down to levels of 0.4 ppb using stripping voltammetry. TiO2/Fe2O3 binary mixed oxides have been prepared using a co-precipitation method, a mesoporous method and sol-gel method. The adsorption capacities of AsIII on mesoporous TiO2/Fe2O3 binary mixed oxides were found at 29.44±2.99, 22.64±1.74 and 21.60±0.33 mg g-1 at pH 5, 7 and 9, respectively. The adsorption kinetics study found the rate constant (k2) 0.02 g mg-1 min-1. The photocatalytic oxidation rate constant (kox) of AsIII onto the surface of TiO2/Fe2O3 binary mixed oxides with synchrotron beam irradiation found in between 0.062 to 0.078 min-1. Additionally, the rate constant (kox) of AsIII phototalytic oxidation in bicomposite suspension with UV irradiation found at 4.37x10-3 min-1. The binding mode of AsIII and AsV onto the surface of TiO2/Fe2O3 binary mixed oxides was to be a bidentate mononuclear edge sharing (2E) complex and a bidentate binuclear corner sharing (2C) complex. Mesoporous TiO2/Fe2O3 binary mixed oxides have been highlighted to be the best bicomposites in this study due to the highest adsorption capacities and ability to photocatalytic oxidation of AsIII to AsV.
Supervisor: Vilar, Ramon ; Weiss, Dominik Sponsor: Thailand
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral