PHOTOSENSITIZED OXIDATION OF BROMIDE TO BROMINE WITH PHTHALIC-ACID DERIVATIVES IN AQUEOUS-SOLUTIONS

The photosensitized oxidation of oxygenated aqueous acidic solutions of potassium bromide was studied, testing the effects of various organic sensitizers. Very effective sensitization was found with aluminum tetrasulfo phthalocyanine tetrasodium salt (AISPc), copper tetrasulfo phthalocyanine tetrasodium salt (CuSPc), cobalt tetrasulfo phthalocyanine tetrasodium salt (CoSPc), phthalic acid and 4-sulfo-phthalic acid. The photo-oxidation of bromide in the presence of AISPc increased both with rising acid concentration and with higher oxygen flow rate, and was not affected by addition of the singlet oxygen quencher 1,4-diazabicyclo-(2.2.2)octane (DABCO). For AISPc, CoSPc and CuSPc, the photoactivity for bromide oxidation continued even after the dyes had become bleached, indicating that the actual sensitizer must be a stable photolysis product of the tetrasulfonated phthalocyanines. In the absence of added bromide, with CuSPc in 2.0M HCl, the photo-oxidation of chloride to chlorine occurred, but at a much smaller rate than that of bromide. © 1990.