Effect of manganese ion on the mineralization of 2,4-dichlorophenol by ozone.

Mineralization of 2,4-dichlorophenol (DCP) was studied by ozone with Mn(2+) as an ozonation catalyst. Laboratory scale semi-batch ozonation experiments were conducted at room temperature. The results showed that trace amount of Mn(2+) accelerated the mineralization of DCP. Total organic carbon removal rate was independent on Mn(2+) dosage at its range of 0.1-0.5 mgL(-1). Dissolved ozone concentration in the solution remained low level in the catalytic ozonation process, which indicated that Mn(2+) catalyzed decomposition of ozone. DCP mineralization was inhibited in catalytic ozonation by the addition of carbonate. Electron spin resonance/spin-trapping technique was used to determine hydroxyl radicals, and the results showed that larger amounts of hydroxyl radicals were produced in catalytic ozonation system than those of single ozonation. Intermediates mainly including aliphatic carboxylic acids were determined qualitatively and semi-quantitatively by GC-MS. And, a general pathway for mineralization of DCP was proposed.