Experimental On Zero-Valent Iron Nanoparticles For Remediation Of Contaminated Water And Sediment

The water pollution is serious in our county. According to the Environment Conditions Bulletin of China in 2013, the surface water environmental quality belongs mildly polluted, and the eutrophication issues were outstanding. Of all the 469 monitoring sections in river systems, 19.3% of them belong ? and ? water quality, and 9% of them below ? water quality. Specifically, to the rivers flow through urban and industrial areas, the water conditions are more serious. The pollutants might be accumulated in the sediments by precipitation, adsorption, biological uptake and other processes. These sediments might accumulate over long periods and could act as new pollutant sources to the overlying water after the water quality has improved. Thus, controlling the pollutants in sediment is significant for water body restoration.We determined concentration and forms of heavy metals including Cr, Cd, Zn, Pb and Cu are evaluated.The methods of Index of Geoaccumulation, Nemerow index method and Potential ecological risk evaluation are applied to evaluate potentially ecological risk. The removal efficiencies of Cr(?), Cd(?), Pb(?) in simulated sediment were studied by CS-NZVI with the experiments, and the removal conditions of the three heavy metal ions were optimized. Moreover, the effect of CI- and pH on the removal rates were discussed, and the kinetic characteristics of Cr(?), Cd(?), Pb(?) removal by CS-NZVI were obtained. In addition, the composition changes of ZVI before and after treatment were characterized by X-ray diffraction,. The main results are summarized as follows.The results show that the mount of Cd and Pb pollution were significant in sediment, and most monitoring sections were beyond Tianjin soil environmental background values. The main form of Cr, Pb, Zn and Cu in sediments were residual and originated state. The rank of evalutation the migration of heavy metals with exchangeable content was Cd> Pb> Zn> Cu> Cr; Risk evaluation research showed that Cu, Zn, Pb, Cd all have reached the level of medium pollution, and Cd in all the parts have exceeded serious pollution level.The content of Cr, Cd, Pb in surface water and sediments were effectively removed by CS-NZVI, and the removal rates can be obtained as 90% and 83%, respectively. The concentration variations of CI-and pH were significantly influenced on the removal rate of Cr(?), Cd(?), Pb(?) of surface water and sediments. When the pH of the reaction system increased from 3.11 to 9.13, the removal rates showed slight upward trend after greatly reduced. The removal rates of Cd(?) and Pb(?) were decreased from 82.32% to 78.17% and 86.23% to 81.25%, respectively. High salinity of environment played a role in promoting the removal of Cd(?) and Pb(?) in sediment with CS-NZVI, but it had no significant effect in the removal of Cr(?).