Investigation Of Degradation Of Organic Pollutants And Inhibition Of Bromate Formation In Catalytic Ozonation Water Treatment Process

The widespread occurrence of pesticides has been found in wastewater, surfacewater, ground water and drinking water. Pesticides show a wide range of persistencein aquatic environments, some of which have been found to resist water andwastewater treatment.As a new and the most promising development in the research of advancedoxidation water treatment, heterogeneous catalytic ozonation has been received increasingattention in recent years because of its potentially higher effectiveness in the degradation andmineralization of refractory organic pollutants and higher stability and lower negative effect onwater quality. In this work, on the basis of previous studies, catalyst carried on alumina whichcoated on ceramic-honeycomb was synthesized, that is β-FeOOH/Al₂O₃/CH. After laboratorystudies, the catalytic ozonation of natual water body containing pesticide2,4-D was carried out incontinuous flow experiments in the fixed bed reactor in order to investigate its feasibility forpractical water treatment. Also the reduction ability of bromate formation was studied in theprocess of flocculation-ozonation and catalytic ozonation of raw water containing bromide. Themain research contents and results are listed as follows:1. Preparation of high efficient ozone catalyst fixed on ceramic-honeycomb.AlOOH sol was prepared with pseudo-boehmite as raw material. The alumina washcoats onceramic honeycomb （CH） was prepared by sol-gel method using the prepared sol as washcoatmodifier for ceramic honeycomb substrate. β-FeOOH was supported on modified ceramic byhydrothermal hydrolysis process with iron chloride hexahydrate as the metal precursor. The resultsclearly indicated the catalyst’s presence significantly improved the mineralization efficiency oforganic pollutants when compared to ozonation alone in continuous flow experiments. In addition,no significant iron ion was detected in the catalyst suspension during the ozonation process, whichindicated the catalyst had good catalytic activity and stability. So that it is a promising material inwater treatment superior to homogeneous catalytic ozonation and separated catalytic ozonation forits no secondary pollution and easy to recycle. Experiments were carried out to search theoptimum reaction conditions of fixed bed reaction, preparing for applying to natural water bodytreatment. 2. High efficient ozone catalyst fixed on ceramic-honeycomb used in natural water treatment.The catalytic activity of the synthesized catalyst was investigated when applied to naturalwater treatment.2,4-D was added into incoming water of the water plant to form aqueous solution.The optimum reaction conditions and catalytic activity of catalysts in the long-term running wasinvestigated in continuous flow experiments in fixed bed reactor. The results showed the presenceof β-FeOOH/Al₂O₃/CH significantly improved the mineralization efficiency of organic pollutantsaqueous solution. β-FeOOH/Al₂O₃/CH is a promising catalyst for actual water for the catalyticability of the catalyst remained stable after30times reuse.3. Flocculation-ozonation and heterogeneous catalytic ozonation of water containing Br-andcontrol of BrO3-generated.It is known that the carcinogenic bromate is formed in the oxidation process ofbromide-containing water. Experiments were taken to test the ability to reduce bromate formationof flocculation-ozonation and heterogeneous catalytic ozonation with synthesized catalystβ-FeOOH/Al₂O₃/CH. The results indicated that the crucial condition for bromate formation waspH. But the formation of bromate could be reduced below the national standard in the circulatoryflow reaction in the fixed bed reactor. Therefore, the catalyst and the fixed bed reactor process arepromising in actual water treatment.