Selectivity and efficiency of biomimetic catalysts in a model system for pulp bleaching

Three biomimetic systems were evaluated for their selectivity in a model sy stem for pulp. FeSO4, Fe-EDTA and hemoglobin, in the presence of H2O2, cons tituted the biomimetic systems. Sodium lignosulfonate and hydroxyethyl cell ulose (HEC) were used as a model system to represent lignin and carbohydrat e fractions in pulp. A simple kinetic model was used to determine kinetic p arameters for depolymerization of each substrate. Point selectivities at tw o different H2O2 concentrations were evaluated on the basis of the resultin g expressions. Hemoglobin demonstrated superior selectivity for lignosulfon ate degradation at a high H2O2 level. The production of hydroxyl radicals f rom each of the biomimetic systems was measured using a chemiluminescence a ssay. For the FeSO4 and Fe-EDTA systems, depolymerization was related to th e amount of radicals generated. The fate of reacted H2O2 was evaluated usin g a specially designed reactor to measure H2O2 consumed by reaction and tha t decomposed. To achieve a given number of chain scission in lignosulfonate , the hemoglobin system consumed the least amount of H2O2.