THE PEROXYMONOCARBONATE ANIONS AS PULP BLEACHING AGENTS. PART 1. RESULTS WITH LIGNIN MODEL COMPOUNDS AND CHEMICAL PULPS

The peroxymonocarbonate mono-anion (HCO(4)(-)) is generated when the bicarbonate anion is added to a H(2)O(2) solution. The mono-anion is believed to have a pK(a) value of ca. 10 and as such would start dissociating to the di-anion (CO(4)(2-)) at pH ca. 8. The mono-anion should demonstrate electrophilic properties, while the di-anion should be a nucleophile. In an alkaline, non-sulfur pulping process such as soda/AQ, Na(2)CO(3) could be obtained from the chemical recovery system and carbonated with CO(2) from a flue gas stream to produce NaHCO(3). In such a case only H(2)O(2) would need to be purchased to generate the peroxymonocarbonate (PMC) anions. Bicarbonate anions could also be produced from the carbonation of solutions containing NaOH, Mg(OH)(2) or mined Na(2)CO(3). One or both of the PMC anions was found to be effective in oxidizing two lignin model compounds as well as lowering the lignin content of kraft and soda/AQ hardwood pulps. The PMC anions were generated in-situ by NaHCO(3) or Na(2)CO(3) + CO(2) addition to dilute H(2)O(2) solutions.