Sonocatalytic–Fenton reaction for enhanced OH radical generation and its application to lignin degradation

The present study demonstrated that the combined use of the sonocatalytic reaction (using ultrasound and titanium dioxide) and the Fenton reaction exhibited synergistically enhanced hydroxyl (OH) radical generation. Dihydroxybenzoic acid (DHBA) concentration as index of OH radical generation was 13 and 115 μM at 10 min in the sonocatalytic reaction and Fenton reaction, respectively. On the other hand, the DHBA concentration was 378 μM at 10 min in the sonocatalytic–Fenton reaction. The sonocatalytic–Fenton reaction was used for degradation of lignin. The lignin degradation ratio was 1.8%, 49.9%, and 60.0% at 180 min in the sonocatalytic reaction, Fenton reaction, and sonocatalytic–Fenton reaction, respectively. Moreover, the sonocatalytic–Fenton reaction was applied to pretreatment of lignocellulosic biomass to enhance subsequent enzymatic saccharification. The cellulose saccharification ratio was 11%, 14%, 16% and 25% at 360 min of pretreatment by control reaction, the sonocatalytic reaction, Fenton reaction, and sonocatalytic–Fenton reaction, respectively.

► This is the first study to combine sonocatalytic and Fenton reactions.
► Sonocatalytic–Fenton reaction showed synergistically enhanced OH radical generation.
► The OH radical generation was applied to lignin degradation and biomass pretreatment.
► Lignin degradation ratio by sonocatalytic–Fenton reaction was 60.0% at 180 min.
► Cellulose saccharification ratio by sonocatalytic–Fenton reaction was 25% at 360 min.