Impact of transducers configuration in a pilot sonoreactor used for nanocellulose production by ultrasound-assisted TEMPO oxidation

For the pulp and paper industry, it is generally believed that nanocellulose will open new market and increase mills profitability. Our research group as shown that the TEMPO - Sodium bromide - Sodium hypochlorite oxidation system, used in nanocellulose production, can be further optimized with the use of low frequency ultrasound. Therefore, a pilot scale flow-through sonoreactor (sonoreactor 1) compatible with such oxidation was developed and many publications were issued. In effort to further optimize the system; a new sonoreactor (sonoreactor 2) with variable transducer configuration was fabricated. The objective of this work is to study the sonochemical efficiency of the new transducer configuration and the impact on the oxidation efficiency. From the Weissler method (potassium iodine oxidation) experiments, free radicals production was found to be dependent on the transducers configuration. For a given frequency and power, the production rate is respectively greater for the star pattern, orthogonal and face to face configuration. However, the increased free radical production was found to have a more subtle effect on the oxidation efficiency, thus carboxylate content of the pulp.