The Controllable Preparation Of Ti₃C₂T_x MXene And Study On Removal Performance Of Cr??? In Aqueous Solution

Metal chromium,Cr(?)is a strong carcinogen with strong toxicity to organisms,especially humans,and is one of the 17 key pollutants recognized by the US Environmental Protection Agency(USEPA).If wastewater containing Cr(?)is introduced into natural water bodies,it will not only destroy the ecological environment,pollute the soil and water sources,but also pose a huge threat to the health of plants and even humans.According to relevant WHO regulations,the content of Cr(?)in drinking water shall not be higher than 0.05 ppm.The adsorption method is one of the effective ways to control heavy metal ion pollution because of its low cost,easy operation,simple equipment and short cycle.Therefore,the construction of new-type,high-efficiency,environmentally friendly and large specific surface area adsorbent materials has important theoretical guiding significance and practical application value for the treatment of Cr heavy metal ion pollution,which is conducive to promoting the friendly and sustainable development of human society.The two-dimensional transition metal carbon/nitride(MXene)material has the characteristics of diverse composition,controlled layer spacing,large specific surface area,good hydrophilicity and abundant functional groups suspended on the surface.It is an ideal carrier for heavy metal ions and can effectively Removal of heavy metal ions shows a certain development prospect and practical application value in the adsorption and degradation of organic pollutants and heavy metal ions.In this thesis,the design and construction of MXene materials that efficiently remove Cr toxic ions is the research goal.By adjusting the chemical composition,surface properties,morphology and pore structure and other influencing factors,a series of MXene materials with different morphologies and chemical compositions were prepared.Using heavy metal Cr ions as probes,the adsorption behavior and mechanism of Cr ions of MXene materials were systematically explored,and the structure-effect relationship between its removal performance for Cr ions and its chemical composition and pore structure was revealed.The main research contents and results of the paper are as follows:(1)Guided by the structure of the MAX phase material,the ball milling method and roasting preparation technology were developed,and the Ti3AlC2 precursor was obtained.After HF etching at different temperatures,a series of three-dimensional accordion structures 3D-Ti3C2Tx MXene were obtained Materials(3D-MX-303,3D-MX-313 and 3D-MX-323),the influence of factors such as morphology,pore structure and surface properties on the removal of Cr(?)ions by 3D-Ti3C2Tx materials was investigated in detail.Among them,the optimal removal amount of Cr(?)ion for the 3D-MX-313 sample at T=298 K and solution pH=1 is 585.33 mg g-1,and its adsorption behavior follows the pseudo-second-order kinetic model and The Langmuir isotherm model adsorbs Cr(?)ions on the surface of a single layer and mainly uses chemical adsorption.The removal mechanism results indicate that Cr(?)ions have undergone an oxidation-reduction reaction on the surface of 3D-Ti3C2Tx,and are reduced to Cr(?)ions,and the Ti-O bond on the surface of Ti3C2Tx is broken,and Cr(?)eventually forms Ti-O-Cr(?)species,thus anchored on the surface of 3D-Ti3C2Tx material.(2)Develop a chemical thermal solution method,using LiF and HCl as etching solutions,and adjust the ultrasonic stripping power to prepare a series of 2D-Ti3C2Tx nanosheet materials(2D-MX-600,2D-MX-800 and 2D-MX-1000),investigate in detail the influence of morphology,specific surface area and pore size on the Cr(?)removal performance of 2D-Ti3C2Tx nanosheets and its adsorption behavior and mechanism.The optimal removal amount of Cr(VI)for the 2D-MX-600 sample at T=298 K and solution pH=1 is as high as 823.33 mg g-1,and its adsorption behavior follows the pseudo second-order kinetic model and Langmuir isotherm model.The removal of Cr(?)by 2D-Ti3C2Tx nanosheet material is higher than that of 3D-Ti3C2Tx,indicating that a large-area single-layer MXene nanosheet is beneficial to expose more active sites,thereby enhancing the migration of Cr(?)Except performance.