Occurrence Of Phthalates In Qian Tang River And Catalytic Ozonation Of Phthalates Using Magnetic Rare Earth Metal As Catalyst

Phthalate esters(PAEs)are mainly used as plasticizers of plastics,which have large production and wide application in the word.It has been shown that PAEs may cause mutagenicity,carcinogenesis and teratogensis.PAEs have become one of the most widespread contaminants in the aquatic environment because of their great consumption,The Qian Tang River is the mother river of Zhejiang Province.For the water quality control of the Qian Tang River,traditional attention has been paid to the conventional pollutants,such as COD,NH3-N,TP and etc,while less attention to the toxic and harmful trace substances,e.g.PAEs.For PAEs,we should not only find out their occurrence in the environment,but also know how to employ effective treatment methods to degrade or eliminate them.Catalytic oxidation is a new advanced oxidation technology,magnetic nano catalysts,which are easy to recover,good stability and high activity,have been interested by researchers.In this study,the Qixi reservoir and Quzhou section(from Kaihua to Longyou section)of the Qian Tang River were selected as the study area according to monitoring sections that set up by Zhejiang Environmental Protection Bureau and the pollution discharge.Twenty-two water samples(including 22 particulate samples)and 21 sediment samples were collected from 22 sampling sites and 16 PAEs in samples were analyzed.The main results are as follows:1.In the Qixi reservoir,the concentrations of PAEs in the water-suspended particulate matter-sediment system were 4.4-16 ug/L?215-2313 ug/g.dw and 0.48-9.1ug/g.dw.In the Quzhou section(from Kaihua to Longyou section),the concentrations of PAEs in the water-suspended particulate matter-sediment system were 6.2-20 ug/L,11-1257 ug/g.dw and 1.5-8.3 ug/g.dw,respectively.The concentration of Diisobutyl phthalate(DiBP)of 16 PAEs was the highest in the water,while the concentration of di(2-ethylhexyl)phthalate(DEHP)was the highest in the particulate and sediment.In the water-suspended particulate matter-sediment system,the main PAEs were dimethyl phthalate(DMP),diethyl phthalate(DEP),di-n-butyl phtalate(DnBP),diisobutyl phthalate(DiBP)and di(2-ethylhexyl)phthalate(DEHP).These compounds were detected in all samples.2.According to the correlation analysis of DMP,DEP,DnBP,DiBP and DEHP of Qixi reservoir in water and sediment,there were not a significant correlation between them,except DnBP and DiBP in the water samples,DEP and DiBP in the sediment samples.The organic matter fractions in the sediments collected from Qixi reservoir were 3.6%-7.4%,and collected from Qian Tang River were 2.5%-8.8%.No significant correlation was observed between the concentrations of PAEs and organic matter fractions.3.The occurrence concentrations of PAEs followed the order of DiBP>DEHP>DnBP>DMP>DEP in the water of Qixi reservoir and Quzhou section,while DEHP>DiBP>DnBP>DEP>DMP in the sediment.In the water column,the concentration of PAEs are dependent on pollution source with discharge that containing PAEs substances.The concentrations of PAEs in the sediment were also associated with n-octanol/water partition coefficients Kow,besides pollution source with discharge that containing PAEs substances.4.The PAEs concentrations of Qixi reservoir and Quzhou section of Qian Tang River in the water and sediment samples were at upper middle level compared with foreign reservoirs and rivers,and relatively low level compared with domestic reservoirs and rivers.For Qian Tang River,the detected concentrations of PAEs were different at different sampling sites,.5.According to the monitoring data and evaluation method,the ecological risk assessment for the water was estimated using zebra fish embryo and algae.DMP has no ecological risk.Except the No.11 sample point of Quzhou section of the Q values of DEP lies in the range of low potential ecological risk,other sampling sites have no ecological risk.The DBP and DEHP did not have a direct ecological risk.However,all of Q values lie in the potential range of low ecological risk.The ecological risk assessment for the sediment was also estimated.The concentrations of DnBP were lower that the standard of 0.7 ug/g by Van Wezel,while the concentrations of DEHP in Qixi reservoir and Quzhou section were higher than the standard.Additionally,three magnetic rare earth catalyst particles of Ce/SiO2@Fe3O4,La/SiO2@Fe3O4 and Pr/SiO2@Fe3O4 for catalytic ozonation DEP were prepared,and some catalytic ozonation experiments were carried out.The main results are as follows:1.The structures and characteristics of three magnetic catalyst particles were analyzed by XRD,XPS and TEM.Results showed that Ce/SiO2@Fe3O4,La/SiO2@Fe3O4 and Pr/SiO2@Fe3O4 all had a spinel structure,and had a ternary structure with a Fe3O4 magnetic core,a SiO2 shell and metal oxides outer layer.The average diameters of three magnetic catalysts were about 100-200 nm.2.The catalysts of Ce/SiO2@Fe3O4,La/SiO2@Fe3O4 and Pr/SiO2@Fe3O4 showed an obviously high efficiency in catalytic ozonation DEP,while operated at initial DEP concentration of 20 mg/L,temperature 30?,pH value 6.2,03/O2 flow rate 100ml/min,and catalyst dosage 0.5g/L,the TOC removal with Ce/SiO2@Fe3O4,La/SiO2@Fe3O4 and Pr/SiO2@Fe3O4 catalyst at 90 min could increase 23.1%,30.1%and 35.6%compared with ozone alone.3.Tert-butyl alcohol(TBA)and adsorption experiments showed that catalytic ozonation DEP followed a radical-type mechanism.Surface hydroxyl groups were the main active sites of three catalysts in promoting hydroxyl generation from aqueous ozone,which increased the removal and mineralization of DEP.The catalytic ozonation process was pH dependent.The optimum pH for mineralization of aqueous solution was about 10.0 in our experiment system.The dissolved metals from three catalysts in the water were lower.According to stability and recyclability test of the catalysts,the catalysts would be helpful in the separation and magnetic recyclability.4.The initial mineralization rate constants of three magnetic catalyst particles for catalytic ozonation DEP were calculated.Pr/SiO2@Fe3O4 possessed a higher initial mineralization rate constant,La/SiO2@Fe3O4 ranked the second.The rate constant had a positive relation with the hydroxyl groups and pH value at zero charge point(pHpzc)of the catalysts,and had no significant relation with the surface area and the concentration of hydroxyl groups per unit area of the catalysts.