| A variety of new nanomaterials are concerned and used in the fields of chemistry andmedical increasingly, which are probably introduced into soil when people synthetize and usethese materials. In this case, most of these nano materials will be sink into the soil layer.However, whether these nano materials will react with heavy metal ions in soil and result inthe change of migration and transformation of heavy metals or not is still kept unkown. Inorder to solve this problem, the releasing characteristics of lead and zinc mining polluted soilfrom Fengxian (FX), Tongguan (TG) and Luonan (LN) were studied. The representativemagnetic nanoparticles Fe3O4and its modified products were prepared, and theircharacteristics of adsorption and desorption with Cd(II) and Pb(II) in aqueous solution wereinvestigated.Finally, the adsorption behaviour of Cd(II) in the soil from Yangling (YL), Zhongxian (ZX) and Fushun (FS) was studied via using amino modified nano Fe3O4.The main obtained results inthis study are detailed as follow:(1)The results indicated that the soil were polluted seriously by the mining process, andthe Cd and Pb release were scale-dependet process which were strong influenced by soilparticle sizes effects and the source of heavy metal pollutants. The Cd and Pb total and TCLPextracted available contents were increased with soil particle size decreasing. The soluble Cdand Pb release process in three soils was a complex heterogeneous diffusion process.(2) Synthetic Fe3O4， SiO2@Fe3O4and3NH2-SiO2@Fe3O4nanopartilces wereparamagnetic and porous.Cd(II) and Pb(II) adsorption process was controlled by aqueous pHwhen using Fe3O4，SiO2@Fe3O4and3NH2-SiO2@Fe3O4as adsorbents; Comared with Fe3O4,the Cd(II) and Pb(II) adsorption capacity on SiO2@Fe3O4and3NH2-SiO2@Fe3O4could beincreased Significantly after modification. The Pb(II)maxium adsorption capacities forFe3O4，SiO2@Fe3O4and3NH2-SiO2@Fe3O4were71.4mg/g,78.7mg/g and88.4mg/grespectively; The Cd(II) maxium adsorption capacities for Fe3O4，SiO2@Fe3O4and3NH2-SiO2@Fe3O4were108.6mg/g,142.8mg/g and167.1mg/g respectively. Cd(II) and Pb(II)adsorption process could be described by Langmuir model. Based on thermodynamicis studyand XPS analysis, it could be concluded that adsorption mechanisms was a exothermicprocess contained physical adsorption and ion exchange. (3) The Cd2+desorption capacity for different size were322μg/g,407μg/g and617μg/g inYangling, respectively. The Cd2+desorption for different size were782μg/g,881μg/g and1011μg/g in Zhongxian, respectively. The Cd2+desorption for different size were662μg/g,705μg/g and772μg/g in Fushun, respectively. Cd2+desorption capacity decreasedsignificantly when added3NH2-SiO2@Fe3O4. The Cd2+desorption capacity for different sizewere106μg/g,157μg/g,192μg/g in Yangling, respectively. The Cd2+desorption for differentsize were302μg/g,350μg/g,510μg/g in Zhongxian, respectively. The Cd2+desorption fordifferent size were122μg/g,131μg/g,135μg/g in Fushun, respectively. On the basis of theCd2+distribution coefficient in nanomaterials (3NH2-SiO2@Fe3O4)-soil-water system, it canbe concluded that the ability of Cd2+absorption by3NH2-SiO2@Fe3O4was the most strongestin these three different soil clay. Adding NH2-SiO2@Fe3O4twice showed that adsorptionstability of Cd2+by3NH2-SiO2@Fe3O4was most strongest. The desorption process of Cd2+with or without adding3NH2-SiO2@Fe3O4in polluted soil could be better described by thepseudo-second-order model. The results showed that after being introduced nanomaterialssuch as3NH2-SiO2@Fe3O4into soil, Cd2+was competitively absorbed by3NH2-SiO2@Fe3O4and soil particles in liquid phase environment and the absorptive ability of3NH2-SiO2@Fe3O4was more stronger than soil particles. In this case, desorption process ofCd2+became more slower. |
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