Scientia Marina, Vol 62, No 3 (1998)

Salt effect on sensitized photooxidations. A kinetic approch to environmental decomposition of marine contaminants

María I. Gutiérrez
Departamento de Química. Facultad de Ciencias Naturales. Universidad Nacional de la Patagonia, Argentina

Susana Criado
Departamento de Química. Universidad Nacional de Río Cuarto, Argentina

Norman A. García
Departamento de Química. Universidad Nacional de Río Cuarto, Argentina


The salt effect on the kinetics of singlet molecular oxygen [O2(1Δg)]-mediated photooxidations of sea water contaminants was investigated. Two families of photooxidizable compounds were employed in the study: anthracene derivatives and phenols. The presence of salt (NaCl in H2O and LiCl in MeCN, in both cases in the range 0-0.45 M) produces changes in the photooxidation rate. For solvent-polarity-dependent reactions, this behavior can be predicted, by knowing the solvent-polarity dependence of the rate constant for chemical reaction of the substrates with O2(1Δ g) in non-saline solutions (kr). For the cases of photooxidations possessing solvent-polarity-independent or scantily-dependent kr values, the photooxidation rates decrease as the salt content in the solution increases, mainly due to a predominance of the physical quenching pathway. In addition, the quantum yield for O2(1 Δg) generation (ΦΔ) was determined in a series of saline solutions, in the range of 0-0.45 M in water and MeCN solutions, in the presence of NaCl and LiCl respectively. The Δ values are independent, within the experimental error on the salt content.

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