| dc.description.abstract | This thesis describes the utilisation and activation of in situ generation of hydrogen peroxide (H2O2) from dioxygen (O2) for corrosion inhibition, disinfection and pollutant degradation. MnCl2· 4H2O and Tiron (disodium 4,5-dihydroxy-1,3-benzenedisulfonate) rapidly remove O2 from aqueous solution at a rate of ~20 mg∙ L^(-1) min^(-1) using hydroxylamine (NH2OH) as reducing substrate. A mechanism is proposed that involves two 1-electron transfers from bound NH2OH to bound O2 to produce H2O2 concomitant with two proton transfers from catecholate oxygen atoms. This system can act as an anti-corrosion formulation as the catalytic reduction of O2 results in the removal of O2 from open aqueous solutions and the in situ generated H2O2 can be used as a biocide e.g. to kill L. pneumophila. The same system, which involves manganese(II) ions (Mn(II)) and Tiron as the co-catalyst for the in situ generation of H2O2, was also utilised for the oxidative degradation of Calmagite (CAL, 2-hydroxy-1-(2-hydroxy-5methylphenylazo)-4-naphthalenesulfonic acid) at room temperature. Percarbonate (HCO4-) was found to be the main reactive species for CAL degradation in the added H2O2 system buffered by carbonate at pH 9.0 in the absence of Mn(II). Manganese(IV)=O (Mn(IV)=O) and manganese(V)=O (Mn(V)=O) are the main reactive species in the added H2O2/Mn(II) system buffered by carbonate and non-carbonate buffers respectively. This system was enhanced by activation using ultrasound and copper(II) ions (Cu2+) as catalyst, forming the Cu2+/O2/ultrasound/NH2OH (COUN) system for the degradation of bisphenol AF (BPAF). Using a two-stage kinetic model, quantitative analysis of the catalytic efficiency showed that Cu2+ was relatively stable in the COUN system in contrast to the Cu2+/H2O2/ultrasound (CHU) system. This work contributes to a better understanding of the use of Cu2+, NH2OH and O2 for the in situ generation of H2O2, as well as the role of Cu2+ and NH2OH in Fenton-like systems. | en_US |
