Abstract
Benzylhexadecyl dimethylammonium chloride (BHDC) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) water-in-oil micro-emulsions were employed to study the influence of medium heterogeneity on singlet molecular oxygen [O2(1Δg)]-mediated degradation of 1-hydroxynaphthalene (1-OHN) and 2-hydroxynaphthalene (2-OHN) in their naphthoate form. The kinetic study in the micellar system, that was considered as a closer model for the environment of contaminants in natural polluted waters, consisted of a comparative work with the process in homogeneous solution, by varying surfactant structure and water content of the micro-emulsion. While it is known that 1-OHN and 2-OHN are rapidly and efficiently photo-oxidised in aqueous medium, time-resolved phosphorescence detection of O2(1Δg) and stationary photolysis experiments demonstrate that both the values for the overall and reactive rate constants for the quenching of O2(1Δg) and the photo-oxidation efficiencies are lowered in BHDC micelles, whereas the photo-oxidative process in AOT micro-emulsions was totally inhibited. Results are interpreted and discussed on the basis of different locations of the probe in the micellar environment.