| Metal organic framework is a synthetic porous material with high specific surface area and high porosity.This material has been applied in the fields of energy storage,catalysis,sensing,environmental treatment and so on.Halloysite is a natural nano tubular material widely existing in nature.It is often used as a template in various fields because of its unique tubular structure,high specific surface area and many modification sites.Polydopamine is a multifunctional coating material that can be bonded to the surface of a variety of materials.In this study,a layer of polydopamine was coated on the surface of halloysite by solution oxidative polymerization with halloysite as the initial material HNT@PDA The characterization of the product proved that the synthetic polydopamine was successfully coated on the nano scale.At the same time,the application research of adsorbing organic pollutants is carried out,and the results are as follows:（1）Nano tubular template with polydopamine shell was synthesized by solution oxidative polymerization when the concentration of halloysite and dopamine hydrochloride was 2 mg/m L.Based on the synthesized template,ZIF-8 was successfully grown on the surface of nanorod template by ultrasonic assisted stirring method when the concentration of Zn（NO3）2 was 10 mmol/L and the concentration of 2-methylimidazole was 20 mmol/L.The synthesized template can also grow Ui O-66 on the surface of the template by hydrothermal synthesis when Zr Cl4 is 5 mmol/L and terephthalic acid is 5 mmol/L.The success of these two synthesis methods proves the universality of the nano rod template coated with polydopamine shell.The template has the advantages of simple,economic and environmental preparation.（2）After the growth of MOF material,MOF coating is formed by dense accumulation of MOF particles and molten MOF nanoparticles.These MOF particles stacked on the surface of nanotubes provide macropores（>50 nm）and mesopores（2-50 nm）and micropores（<2 nm）derived from this hierarchical structure for the composite,and enhance the mechanical stability.（3）The polydopamine layer coated on the nanotube anchors the metal ions on the surface of the prepared nanotube template through chelation with the metal.MOF is a highly ordered crystal synthesized by metal ions and organic ligands through coordination bonds.Taking the metal ions anchored on the surface of the nanotube template as seeds,and then placing them in the system containing organic ligands,MOF can grow on the nanotube.（4）The application of HNT@PDA@ZIF-8 in the adsorption of hydroquinone,tetracycline and Rhodamine B dyes in water was explored.Compared with the adsorption capacity of pure organometallic framework,the composite nano materials synthesized in this study have obvious advantages in the adsorption effect of Rhodamine B.The adsorption process of Rhodamine B on composites was studied,the adsorption of Rhodamine B by HNT@PDA@ZIF-8 is closer to Temkin model,indicating that the interaction between HNT@PDA@ZIF-8 and Rhodamine B leads to a linear decreasing relationship between the adsorption heat of all molecules on the adsorbent surface and the coverage,and the binding energy is evenly distributed,and the whole adsorption process is exothermic adsorption.The adsorption process of Rhodamine B by HNT@PDA@ZIF-8 conforms to the pseudo second-order kinetic equation.The adsorption process of Rhodamine B by HNT@PDA@ZIF-8 is controlled by chemical adsorption mechanism. |
