Effect Of Metal Cations On Adsorption Of Anionic Pollutants By Carbon-based Nanomaterials

With the deepening of industrialization,the dye industry has entered the era of large production.A large number of ionic dyes discharged into the environment during the processing of raw materials threaten human health.Removal of anionic dyes is tricky under natural conditions.Carbon materials such as biochar and graphene are of-ten used as adsorbents for the treatment of ionic pollutants produced by dye processing due to their porous structure,rich functional groups,and stable surface structure.At present,most of the researches on dye pollutants focus on the adsorption capacity of different types of adsorbents to each ionic pollutant formed by processing dyes.How-ever,the influence of different adsorbent characteristics and types of different pollutants on the adsorption capacity under different p H environmental conditions has been ignored,and the removal effect of a large number of anionic pollutants produced in the dye industry has been limited.The three-dimensional graphene(3D-GO)in this paper is a carbon-based material with a three-dimensional structure formed by graphene oxide(Dimensional Graphene,2D-GO)through hydrothermal self-assembly method with excellent characteristics such as large surface area and strong electrical conductivity.In the environmental field,3D-GO as an adsorbent has attracted much attention because of its huge specific surface area and excellent adsorption performance.In recent years,it is not uncommon to im-prove the adsorption performance of three-dimensional materials through the method which with 2D-GO as the skeleton and adds cross-linking agents to synthesize foreign substances with high density.However,few studies have reported that in the natural state the adsorption performance and mechanism of composites that are freely formed by hydrothermal self-assembly only without the addition of cross-linking agents.This study simulated the effect of free metal ions(Ag⁺?K⁺?Ca²⁺?Cu²⁺?Al³⁺)on the adsorption of anionic pollutant o-chlorobenzoic acid(2-CBA)by carbon nanotubes(CNTs)under different p H environments and explored the effect mechanism of the co-existence of metal ions(Ag⁺?K⁺?Ca²⁺)for the adsorption of anionic dye methyl orange (MO)on three-dimensional graphene oxide-based materials in different p H environ-ments By comparison,the mechanism of the influence of metal ions in different states on the adsorption of anionic dyes on carbon materials was analyzed and the contribution of metal ion valence state and hydration radius in the adsorption process was researched.At the same time,we explored the differences in adsorption properties between carbon materials of different dimensions.The results showed that free metal ions inhibit the adsorption of 2-CBA by CNTs and the inhibition was controlled by the ion hydration radius at low p H.At high p H,free metal ions promoted the adsorption of 2-CBA by CNTs.The metal ions with the higher valence state and the smaller hydration radius had the stronger ability of pro-moting 2-CBA adsorption.While the metal ions coexisting in the three-dimensional material whether the hydration radius or the valence state all had no obvious effect on the adsorption,but compared with the two-dimensional structure material,the ability of the three-dimensional structure of the material to adsorb anionic pollutants was greatly improved and it had great application value for the treatment of dye wastewater in the future.