SALT EFFECT ON SENSITIZED PHOTOOXIDATIONS - A KINETIC APPROCH TO ENVIRONMENTAL DECOMPOSITION OF MARINE CONTAMINANTS

The salt effect on the kinetics of singlet molecular oxygen [O-2((1)De lta(g))]-mediated photooxidations of sea water contaminants was invest igated. 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) produce s changes in the photooxidation rate. For solvent-polarity-dependent r eactions, this behavior can be predicted, by knowing the solvent-polar ity dependence of the rate constant for chemical reaction of the subst rates with O-2((1)Delta(g)) in non-saline solutions (li): For the case s of photooxidations possessing solvent-polarity-independent or scanti ly-dependent k values, the photooxidation rates decrease as the salt c ontent in the solution increases, mainly due to a predominance of the physical quenching pathway. In addition, the quantum yield for O-2((1) Delta(g)) generation (Phi(Delta)) was determined in a series of saline solutions, in the range of 0-0.45 M in water and MeCN solutions, In t he presence of NaCl and LiCl respectively. The Phi(Delta) values are i ndependent, within the experimental error on the salt content.