Research On Performance And Mechanism Of Removing ²¹⁰Pb（Ⅱ） From Aqueous Solution By Coated Nanoscale Zero-valent Iron

Our country is facing the unreasonable energy structure and energy shortages.The nuclear power is a kind of clean energy which has been vigorously developed in our country. The ecological environment and human health can be threatened by the radioactive water. So the treatment of radioactive water counts most. In recent years,the nanometer zero-valent iron has been widely used in the treatment of poluted water.Nano zero-valent iron(n ZVI) has not only the characteristics of zero-valent iron but also the high reactivity and large specific surface area, however, their chemical property is unstable, and it is easy to agglomerate and oxidation. Some related studies investigated that n ZVI coated with CMC can effectively supress the agglomerate and oxidation.Coated nano zero-valent iron with carboxymethy(n ZVI/CMC) was preparation by liquid phase reduction, n ZVI and coated nZVI/CMC were used to remove 210Pb(II)from aqueous solution.The effects of coated nZVI/CMC and n ZVI’s dosages, solution p H value, initial 210Pb(II) radiactive concentration, contact time and temperature has been studied. The mechanism of 210Pb(II) removal on coated n ZVI/CMC and n ZVI was investigated by isothermal model, thermodynamic model and kinetic model. The characterizations of composite materials mainly include scanning electron microscope(SEM), energy spectrum(EDS), specific surface area(BET), X-ray diffraction(XRD).The results of the study are as follows:( 1) The coated nZVI/CMC and nZVI have high removal efficiency for210Pb(II).The results showed that when the pH is 5.5, the coated n ZVI/CMC concentration is 0.55 g·L-1,the contact time is 60 min, the removal rate are 99% and97% respectively.( 2) It has found that the Freundlich isothermal adsorption model can better describe the adsorption process, it mainly belongs to physical adsorption and multilayer adsorption. The adsorption process belongs to physical adsorption according to the thermodynamic parameters.. So comprehensive fund that the process of two kinds of adsorbent remove 210Pb(II) from aqueous solution are physical adsorption and chemical adsorption.( 3) SEM shows that: Coated type zero-valent iron nanoparticles into hammer shape mesh structure and not agglomerate. Contrastive analysis of EDS, thecarboxymethyl cellulose has effectively coated nZVI/CMC. more than 2% 210Pb(II) has been adsorbed on the surface of the two materials, which shows coated n ZVI/CMC and nZVI have high efficency to remove 210Pb(II) from aqueous solution. The XRD analysis shows coated nZVI/CMC and nZVI only have 44.59 ° diffraction peak of alpha Fe0(110) crystal plane before reaction. Fe2O3,Fe OOH and Fe3O4 crystal plane diffraction peak was observed after reaction. BET suggested the n ZVI before and after coating specific surface area are 28.44 m2·g-1 and 39.97 m2·g-1 respectively. So the coated nZVI/CMC have smaller particle size and higher specific surface area.and the problem of easily agglomerate and oxidation of nZVI has been solved.