Singlet oxygen mediated degradation of Klason lignin

After some results concerning photochemical generated singlet oxygen on lig nins from steam explosion, the reactions of chemically generated singlet ox ygen with Klason lignins from pine and beech are described. Singlet oxygen was produced through the reaction of hydrogen peroxide with sodium hypochlo rite. The degradation of lignin was followed by uv spectroscopy and gel per meation chromatography. Extensive degradation of the lignins was observed w hen 20 mg of Klason lignin was treated with 1 ml of 30% hydrogen peroxide a nd 8.56 mi of 1.093 M sodium hypochlorite. In the uv spectra registered aft er the treatment with singlet oxygen the absorptions typical of lignin (210 -220 nm) and 250-280 nm were completely absent. The gpc analysis of lignin after a treatment with 0.1 mi of hydrogen peroxide and 0.86 ml of sodium hy pochlorite showed a clear reduction of signals due to the lignin and a shif t to lower molecular weight. The potential use of this procedure in the ble aching procedure was tested by using recycled paper. A maximum reduction of 51% in the amount of lignin in this paper was observed. (C) 1999 Elsevier Science Ltd. All rights reserved.