Enhanced sonochemical decomposition of 1,4-dioxane by ferrous iron.

The enhanced ultrasonic decomposition of 1,4-dioxane by the addition of ferrous iron (Fe(II)) was investigated at 205, 358, 618, and 1071 kHz. The total organic carbon (TOC) remaining was also determined at each frequency. Addition of Fe(II) improved the 1,4-dioxane decomposition rate and mineralization efficiency at all frequencies studied. A nearly four-fold increase of the rate constant was observed at the optimal Fe(II) concentration and a frequency of 205 kHz. In the presence and absence of the iron, the fastest overall degradation and mineralization of 1,4-dioxane took place at 358 kHz where 95% of the initial 1,4-dioxane was removed after 50 min. Finally, although reduced, the ultrasonic decomposition of 1,4-dioxane was still significant at all frequencies in the presence of the hydroxyl radical scavenger bicarbonate.