Options for chemical modification of wastes from a Brazilian hardwood species and potential applications

摘要

Two pathways for chemical modification of wastes from an Amazon hardwood species named Cordia goeldiana were proposed in this work. Variations in reaction time (2 h or 0.5 h) and temperature (80 and 150°C), besides reaction medium (mechanical stirring or pressurized closed system) were tested for alkali treatment. NaOH at 5% was kept for both conditions. Afterwards, bleaching with H_2O_2 and NaOH was performed, but reaction conditions were held constant for both pathways. In general, the mild alkali treatment resulted mainly in the removal of extractives and hemicelluloses from the raw sawdust. The onset temperature and crystalline index increased. On the other hand, the use of higher pressure and temperature in alkali treatment at closed system had a remarkable lignin removal and crystalline index increase without changing cellulose polymorphism as the main effects, but thermal stability became lower. Apart from mineral residues removal, bleaching had negligible effects on fiber properties, suggesting that this procedure could be avoided.