Adsorption Characteristics Of TiO₂-CNTs For Li⁺、Na⁺Removal Fromaqueous Solution

All the alkali metals of the seawater are the precious resources,and adsorption isan important method to removal rare material from the seawater.In this paper, westudy the adsorption characteristics of Li+、Na+onto the carbon nanotubes(CNTs) andTiO2-CNTs.Firstly, the carbon nanotubes (CNTs) are treated by mixture acid of H2SO4/HNO3,and using hydrothermal to synthesize a composite materials—TiO2-CNTs. Theexperimental materials are examined by SEM、FTIR spectrometer、X-ray diffraction.Experimental results indicate that after the oxidized treatment, carbon nanotubes(CNTs) are beginning to become smooth and more functional groups are generated onthe surface of the CNTs providing various adsorption sites, and increasing theadsorption capacity and surface area. Using hydrothermal synthesize a kind ofcomposite materials—TiO2-CNTs. The average diameter of TiO2is about13nm, andthe result indicates a majority of anatase.Secondly, the effects of temperature, the initial concentration of Li+、Na+andadsorbents on the adsorption are investigated. The adsorption amount of ions(Li+andNa+)decreases with the temperature increasing and increases with the initialconcentration increasing, that is to say, high temperature is not beneficial to absorbions. A comparative study on the adsorption of Li+, Na+between oxidized CNTs andTiO2-CNTs composite was also conducted and found that TiO2-CNTs composite havea higher adsorption capacity for Li+, Na+than oxidized CNTs. Oxidized CNTs andTiO2-CNTs composite are much easier to adsorb Li+than Na+. Moreover, bothFreundlich and Langmuir model are appropriate to describe the adsorptioncharacteristics of Li+、Na+on oxidized CNTs. The adsorption characteristics of Na+on TiO2-CNTs is more fit for Langmuir model than Freundlich model, and theadsorption characteristics of Li+is more fit with the Freundlich model than Langmuir model. At274K, the absorption energy of Na+(G0)onto the oxidized CNTs isabout-57.36mev which less than the absorption energy of Na+onto TiO2-CNTs (about-61.84mev). These value indicates that the adsorption process of Li+, Na+on oxidizedCNT and TiO2-CNTs are physisorption.