THE PHOTODEGRADATION OF LIGNINS IN THE PRESENCE OF HYDROGEN-PEROXIDE

The photodegradation of lignins in solutions containing hydrogen perox ide was studied. At basic pH, the reaction is at least seven times mor e efficient than in acid solution, where only hydroxyl radicals are fo rmed. Evolution of carbon dioxide and loss of mass can be observed in basic solution. The role of certain functional groups was determined: alpha-carbonyls and phenols favour decomposition, and their reduction or derivatization leads to a decrease in the photodegradation efficien cy. The presence of carboxylate groups and an increase in molecular we ight lead to a decrease in the reaction efficiency. Evidence for the p articipation of singlet oxygen as a reactive species; in the reactions at alkaline pH, generated by the decomposition of hydrogen peroxide, is presented.