RESUMO
Converting paper-grade bleached Kraft pulp into dissolving pulp using eco-friendly chemicals on-site at the mill is a challenge for the pulp industry. In this study, two oxidation systems are evaluated: the first one is based on the use of hydrogen peroxide at various levels of alkalinity; the second one investigates the use of sodium periodate followed by hydrogen peroxide to convert aldehydes into carboxyls and enhance their hemicelluloses removal. Our results have shown that when using only peroxide, the removal of hemicelluloses was not sufficient to improve the pulp's dissolving ability. Conversely, the periodate-peroxide system proved to be more efficient. Results regarding the pulp purity, solubility, degradation (pulp viscosity and cellulose molecular mass distribution), brightness, and its potential applications were discussed.
RESUMO
Microfibrillated cellulose (MFC) is an emerging cellulosic material that has shown enormous potential in various industrial sectors such as food packaging, cosmetics, pharmaceuticals, filler for cement and paper, and others. Yet, there is still the need to improve its processing in order to reach its full potential. Despite research efforts for the production of MFC, the production volumes remain low because the costs of these products are hardly competitive with synthetic polymers. The present study investigates the conversion of bleached Kraft pulp into MFC using three different oxidative treatments: (1) oxidation with sodium periodate followed by oxidation with hydrogen peroxide to enrich the pulp with carboxyl groups; (2) activation of hydrogen peroxide with copper to produce hydroxyl radicals; and (3) use of hydrogen peroxide alone in alkaline medium. Treatments (1) and (2) allowed producing interesting MFC with reduced energy consumption.