ULTRASOUND-ASSISTED HYDROGEN PEROXIDE BLEACHING OF A SOFTWOOD THERMOMECHANICAL PULP

This research has evaluated the impact of ultrasound irradiation on the bleaching of TMP with hydrogen peroxide. More precisely, the influences of irradiation power, ultrasound frequency, and reaction time on pulp brightness have been examined. The results indicated that high brightness could be achieved with a dominant ultrasonic mechanical effect generated at low power (500 W) and low frequency (68 kHz) along with a relatively short bleaching time of 30 min. The reverse results occurred when higher power (e. g., 1000 W), higher frequency (e. g., 170 kHz), and longer reaction time (e. g., 90 min) were used because the chemical effect, which promotes cellulose and lignin degradation, became dominant under these conditions. Statistical analysis showed that up to 74.4% of the brightness response was accounted for by ultrasonic frequency, ultrasonic power, and reaction time with 95% confidence.