Development of mathematical models for describing organosolv pulping kinetics of fungally pretreated wood samples

Eucalyptus grandis wood samples decayed by white- and brown-rot fungi were cooked at 180 degrees C for 5 to 100 min with methanol/water (78:22 v/v) co ntaining 25 mM of CaCl2 and 25 mM MgSO4. Mathematical models for describing organosolv pulping kinetics of the fungally pretreated samples were develo ped to estimate delignification constants, and also rate constants for xyla n and wood mass solubilization. These models had high R-2 values and were a ble to predict pulp yield, as well as lignin and xylan contents during the process at 99% confidence level. Delignification of undecayed control sampl es had a rate constant of 2.0 x10(-2) min(-1) for the bulk phase. Most deca yed samples presented delignification constants higher than those of the co ntrol. Some decayed samples exhibited an additional delignification phase a t the beginning of the process, which was characterized by a low solubiliza tion rate. These samples required insertion of an additional term in the mo del to represent this phase.