Oxidation of bisphenol-A by ozone microbubbles: Effects of operational parameters and kinetics study

The removal of bisphenol-A (BPA) from aqueous medium by ozone microbubbles (OMBs) was studied in this work. The removal efficiency of BPA was improved from 41 to 98% within 600 s of ozonation when the initial pH of the medium was increased from 3 to 7. The stoichiometric ratio of the moles of ozone consumed to the moles of BPA removed was found to be in the range of 0.228–0.276 at pH 7 and 0.125 mol m −3 initial concentration of BPA. A considerably high range of ozone utilization efficiency (i.e., 52%–86%) for the complete removal of BPA was achieved by using the OMBs. Based on the TOC removal, three stages of ozonation (i.e., 0–0.6, 0.6–2.5, and 2.5–3.0 ks) were observed. Their corresponding (observed) reaction rate constants were 294.1, 1365.3, and 2477.7 dm 3 mol −1 s −1, respectively. The oxidation of BPA by ozone followed a first-order kinetics with respect to both BPA and ozone, and an overall second-order kinetics. The Hatta number was low (i.e., 0.01–0.054), which proves that the mass transfer resistance was negligible, implying that the rate of mass transfer was enhanced by the OMBs.