Highly efficient degradation of dimethyl phthalate from Cu(II) and dimethyl phthalate wastewater by EDTA enhanced ozonation: Performance, intermediates and mechanism

In this study, the presence of Cu(II) ions was found for the first time to severely inhibit +-dimethyl phthalate (DMP) degradation by ozone due to the formation of the stable complex Cu(II)-DMP. However, 100% DMP removal was rapidly reached when ethylenediamine tetraacetic acid (EDTA) was added with a Cu(II)/EDTA molar ratio of 3:1. Subsequent studies indicated that Cu(II)-DMP is sequestrated by EDTA, then DMP was degraded and Cu(II) was removed by precipitation. The freshly formed Cu-EDTA 2− and organic nitrogen intermediates further decomposed O 3 into OH, which induced to the rapid degradation of DMP. The k obs of Cu-EDTA/O 3 were 9–10 times greater than the k obs of DMP removed by ozonation alone within 10 min. The reaction mechanism involved a OH generation was proposed. The OH and O 2 - are generated from the rapid reaction between ozone and EDTA. Acting as a more strongly negative species, the specific Cu(II) in Cu-EDTA complexes is more inclined to react with O 2 - to give Cu(I), accelerating the forward reaction to produce more OH. The synergistic removal of DMP and Cu(II) can be achieved after reaction. Therefore, this study provides an effective method to dispose metal ion and organic pollutant wastewater.