Study Of Adsorption And Mechanism Of Ferrocyanide On Goethite And Gibbsite

With the rapid development of industry,a large amount of cyanide-containing waste liquid and residue are discharged into the environment.Because of the wide variety of cyanides which can be converted into each other,and free cyanide compounds have strong toxicity and migration.Therefore,people pay a growing attention to the problem of cyanide pollution in the soil.Cyanide in soil are dominated by ferrocyanide compounds and ferricyanide compounds.Although the ferrocyanide compounds are considered to have a lower toxicity and higher stability than free cyanide compounds,but under certain conditons it will be decomposed to free cyanide compounds and enhance the potential environmential risk.Some iron oxides and aluminum oxides in soil have certain adsorption capacity for ferrocyanide.The study of adsorption behavior and adsorption mechanism of ferrocyanide on active minerals in soil are important to reduce the risk of cyanide in the environment and repair the cyanide polluted soil.In this paper,the laboratory synthetic goethite and commercially available gibbsite were consider as adsorbents and use X-ray diffractometer（XRD）,scanning electron microscopy（SEM）,specific surface area and Zeta potential for their characterization.The adsorption behavior of potassium ferrocyanide on goethite and gibbsite were studied by different adsorption experiments and the effect of ionic strength and pH value on the adsorption was investigated.FTIR and XPS were applied to the surface microscopic information of iron ore and gibbsite was characterized.The Charge Distribution–Multisite Surface Complex（CD-MUSIC）model was used to simulate experimental data,and potassium ferrocyanide was obtained in goethite.Adsorption morphology and adsorption mechanism on gibbsite.Through research,the main conclusions are as follows:（1）Under the condition of pH=4,the ionic strength has a significant effect on the adsorption of goethite and gibbsite on potassium ferrocyanide and the adsorption amount decreases with the increase of ionic strength.However,the effect of ionic strength on the adsorption of potassium ferrocyanide on goethite and gibbsite is not obvious and adsorption mechanism is mainly the inner-sphere complexation generated at pH>5.（2）The pH value of the solution have a significantly affects on the adsorption of ferrocyanide on goethite and gibbsite.Acidic conditions favor the adsorption of ferrocyanide on goethite and gibbsite and the adsorption capacity were decreases with the increase of pH value of the solution.Under the same pH condition,the adsorption capacity of ferrocyanide on goethite is obviously higher than gibbsite.（3）According to the results of FTIR,XPS and CD-MUSIC models simulation data,the surface sites of goethite with potassium ferrocyanide formed a monodentate complex≡Fe[Fe（CN）₆]^3.5-at pH=5.1,monodentate complex≡Fe[Fe（CN）₆]^3.5-and bidentate complex≡Fe₂[Fe（CN）₆]^3-were formed at pH=6.75.Potassium ferrocyanide and gibbsite surface sites form a bidentate double protonated complex≡AlH₂[Fe（CN）₆]^1.5-in pH=5.1and pH=6.75.