ANALYSIS OF HYDROXYL RADICAL GENERATED IN ELECTROLYZED STRONG ACID AQUEOUS-SOLUTION BY ELECTRON-SPIN-RESONANCE SPECTROSCOPY

A hydoxyl radical, which acts as an active oxygen radical, has been in vestigated in an electrolyzed strong acid aqueous solution by electron spin resonance spectroscopy. The hydroxyl radical is detected as two different spin adducts of 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and N-[(1-oxido-4-pyridinio) methylene]-t-butylamine N-oxide. The amount o f DMPO-OH spin adduct has not been changed for ca, 10 days in sealed b ottles. The DMPO-OH spin adduct is gradually increased after DMPO addi tion into the solution where sodium sulfate is used as an electrolysis promoting reagent instead of sodium chloride. It is suggested that th e hydroxyl radical is produced from a precursor like a peroxodisulfate ion, which is derived from the sulfate. The amount of generated hydro xyl radical can be controlled by current density and sulfate concentra tion in the supplied water, where sodium chloride is used in general a s the promoting reagent.