Preparation method of nano goethite

The invention discloses a preparation method of nano goethite, which specifically comprises the following steps: air-drying soil, grinding, uniformly mixing, settling, centrifuging at a high speed, standing, collecting supernate, separating the supernate containing nano particles through an asymmetric flow field flow meter, and freeze-drying to obtain nano goethite particle powder. According to the method, the goethite nanoparticles are fully dispersed, the original structures, components and properties of the goethite nanoparticles are guaranteed, the loss of the goethite nanoparticles in the dispersion process and the preparation process can be reduced to the maximum extent, and the goethite nanoparticles with the particle size smaller than 200 nm are accurately prepared; compared with the prior art, the method has the advantages that the requirements of some special fields with strict requirements on the particle size of goethite can be met, and a large amount of nano goethite can be rapidly and efficientl