Preparation And Characterization Of 2D Kaolinite Nanosheets And Their Adsorption Properties Of Pb(Ⅱ)

Kaolinite minerals are widely distributed and easily available in China,and they have good adsorption properties due to their unique AB surface layer structure.Therefore,kaolin is extremely advantageous for the treatment of water pollution in low cost.In view of the low efficiency of kaolin minerals for remediating polluted water,this thesis used different methods to prepare 2D kaolinite nanosheets with fewer layers in high yield,and applied them to adsorb heavy metal Pb（Ⅱ）and studied their adsorption properties.The main research contents and results are as follows:（1）Dimethyl sulfoxide（DMSO）was inserted into the interlayer of kaolinite by using the direct intercalation method.The characterization results show that the intercalation rate is 100%.Using intercalation composite（DMSO-Kaol）as kaolinite precursor,the natural organic polymer chitosan was inserted into its interlayer to form chitosan-kaolinite exfoliated intercalation composite.Then,the chitosan in the composite was removed away by dilute acetic acid solution.A series of characterization showed that the method can effectively obtain two-dimensional kaolinite layers with an average thickness of about 4.3 nm.（2）N-methylpyrrolidone（NMP）aqueous solution was used to replace the intercalated DMSO and the product was washed with water under ultrasonic conditions.The composition and structure analysis showed that the nanocrystalline kaolinite with less lamellar layer can be obtained by ultrasonic water bath stripping method with an average thickness of about 3.3 nm.（3）The strong oxidizing small molecule hydrogen peroxide（H₂O₂）was mixed with DMSO-Kaol to make the DMSO and H₂O₂ react fully.The energy produced by the reaction can break the hydrogen bond between layers and achieve an excellent exfoliation effect.The average thickness of kaolinite nanosheets is about 2.1 nm.（4）The adsorption properties of Pb（Ⅱ）on delaminated kaolinite products have been studied.The results indicated that the adsorption efficiency of 2D kaolin nanosheets was higher than that of the original kaolinite if the pH did not reach the Pb（Ⅱ）precipitation value.The highest adsorption efficiency of kaolinite and the three exfoliated products were 86.42%and 96.36%,96.48%and 88.54%respectively,and their maximum adsorption capacity were 24.76 mg/g,32.60 mg/g,33.59 mg/g and33.91 mg/g,respectively.