Contributions of ultrasonic wave, metal ions, and oxidation on the depolymerization of cellulose and its kinetics

Abstract

Contributions of ultrasonic wave, metal ions and oxidation on the degree of polymerization (DP) of microcrystalline cellulose (MCC) were evaluated. Five transition metal ions, namely, Ni2+, Cu2+, Co2+, Mn2+, and Fe2+, were selected. H2O2, as an oxidizing agent, was also investigated. Changes in the structure of MCC induced by the ions were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, and field-emission scanning electron microscopy. Results indicated that DP decreased by 16.6%, 32.8%, 47.9% using U-MCC, Ni2+/U-MCC, and ONi2+/U-MCC, respectively. DP of MCC was reduced from 195 to 101.5 under ONi2+/U-MCC due to the destruction of interchain-hydrogen bond. Kinetic of depolymerization process for MCC obeyed the equation: DP = 102.2 + 93.8e−0.000798t, with activation energy of 17.33 kJ/mol. The result suggests that depolymerization of MCC was mainly a physical process at these conditions, and the interchain-hydrogen bond were disrupted. This study is beneficial for the deep hydrolysis and its utilization of MCC.