Photocatalytic Degradation And Mechanism Of Phthalic Acid Esters In Water Using Zinc Oxide

Phthalic acid esters (PAEs) are environmental hormones, which disrupt endocrine ofhuman and animals. In this work, the removal performances of PAEs in water by zinc oxidenanorods were analyzed. The influence of different degradation parameters and the bestdegradation conditions were discussed. This subject provided a promising method for thetreatment of waste water containing PAEs.Zinc oxide nanorods were obtained by hydrothermal method, which showed the averagediameter was around60nm. The photocatalytic degradation of PAEs with zinc oxide as thecatalyst was in aqueous solution. The major intermediates during the degradation process wereexamined and analyzed by GC/MS. The reaction mechanism was concluded according to this.The results showed that:(1) The various degradation parameters, such as photocatalyst loading, initial pH, andillumination time had obvious influence on the photocatalytic degradation. The best degradationcondition of DBP was concluded that: illumination continually, the concentration of ZnO was30mg/L, and the initial pH was6.0. In this condition, DBP could be degraded efficiently byzinc oxide, and the efficiency was87.8%in1hours. It was found that the photocatalyticdecomposition reaction followed a first-order kinetic law.(2) The PAEs solution composed of DMP, DEP and DBP5mg/L was researched. The bestdegradation condition was: illumination continually, the concentration of ZnO was60mg/L,and the initial pH was6.0. In this condition, the degradation efficiency of PAEs was87.8%in1hour. All the photocatalytic decomposition reaction of the three PAEs followed a first-orderkinetic law. The constant of action was: DMP＞DEP＞DBP. The process has better removal forthe lower weight molecules PAEs than for the higher weight PAEs.(3) The reaction mechanism and range of DBP were studied. The major intermediatesduring the degradation process were examined and analyzed by GC/MS, included monobutylphthalate, dipropyl phthalate, butyl benzoate, and the end product was butyl benzoate. The pHof the reaction was decreased, which support the conclusion.