Extraction, Characterization And Adsorption Of Inorganic Nanoparticles In Soils

Based on the rapid development and relevant research of environmental nanoscience, this paper established the method for extraction and characterization of inorganic nanoparticles in soils, and researched their formation process and the environmental behaviors. It was expected to provide theoretical basis in environmental remediation using nanoparticles, and also promote the establishment and development of nano-soil science. Soil nanoparticles were extracted by using a combination procedure of sieving, sedimentaion, centrifugation, and ultrasonication, and extracted nanopartilces were characterized by Malvern Nano-ZS, X-ray diffraction(XRD), field scanning electron microscopy(FSEM) and high-resolution transmission electron microscopy(HR-TEM) equipped with EDS.Particle size distribution(PSD) of extracted nanoparticles from red soil, black soil and dark loessial soil showed a normally distribution pattern with the peak of about 80 nm. XRD analysis showed the existence of several kinds of crystalline clay mineral phases including kaolinite, illite and iron oxide. HR-TEM/EDS observation on soil nanopartilces indicated heterogeneous morphology, structure, crystallization among the three different samples. The morphology of soil nanopartilces exhibited spherule, rod-like, needle-like, and irregularly shaped particles. In particular, Fe-aluminosilicate structure which was widely identified distributed was a key factor in the environmental interaction. Lattice spacing was calculated from the high-resolution images, and the main result were 0.266-0.277 nm and 0.333～0.334 nm, which represented hematite or maghemite, and silicon oxides.The adsorption of Cd by inorganic nanoparticles of soils was fitted to Henry and Freundlich isotherm equations. The three samples followed the order:dark loessial soil>red soil>black soil, of which the adsorption capacity of black soil was significantly lower than the two others. The adsorption of Cd was possibly related not only to content of the free iron oxides, but also to crystalline type of the oxides in the nanoparticles, which were decided by the different formation process among the three soils. In addition, the variable charge carried by inorganic nanoparticles also had some important effect on the adsorption reaction. The order of adsorption efficiency has the following order of red soil>dark loessial soil>black soil. Date from the experiment of adsorption efficiency were all above 96%, which suggested the heavy metal of Cd, in such experimental condition, was almost completely removed by nanoparticles.