Kinetic decomposition of ozone and para-chlorobenzoic acid (pCBA) during catalytic ozonation

The decomposition of ozone and para-chlorobezoic acid (pCBA) using ozone and ozone/goethite were investigated under various conditions to define the characteristics of ozonation and catalytic ozonation. A continuous analysis of the kinetics of the reaction between ozone and pCBA was established, and the decay rate of ozone and pCBA with/without goethite was determined. The decay rate of ozone in the presence of goethite was much higher than in the absence of goethite and was strongly pH dependent due to the reactivities of ozone with the three surface species (≡FeOH2+, ≡FeOH, ≡FeO−) of goethite. The removal pattern of ionized pCBA at different pHs agreed well with the instantaneous ozone demand. The removal rate of pCBA and instantaneous ozone demand with/without t-butanol at different pHs were compared to elucidate the reaction mechanisms associated with the three reaction sites: (i) on the surface of the catalyst, (ii) at the catalyst–solution interface, and (iii) in the bulk solution.