Investigation of iron(II) adsorption from aqueous solutions on anthracite-based modified carbon material
N. V. GORA, D. A. CHERNYSHEV, O. V. BELYAEVA
Kemerovo State University, Kemerovo, Russia
Keywords: iron(II) ions, adsorption, carbon sorbent modification
Abstract
The possibility to increase the adsorption capacity of the sorbent Purolat-Standard, a cheap anthracite-based carbon material (CM), towards iron(II) ions was studied. Sulphuric acid, aminoethanoic acid, and their combination were used as modifiers. The effect of modification on the porous structure and surface state of the analysed sorbents was examined. It has been found that only treatment with sulphuric acid has a significant impact on the structural characteristics of the carbon material. A comparison of microphotographs of the samples before and after iron ion adsorption suggests its adsorption on the surface of macropores. It is shown with the help of X-ray diffraction analysis that the chosen modification methods do not change the phase composition of the sorbents. According to the data of spectroscopic studies, modification of sorbent samples leads to changes in the qualitative and quantitative composition of surface groups. The adsorption of iron(II) ions on the initial and modified samples of carbon material was studied under equilibrium conditions. It was found that using AEA as a modifier fundamentally alters the shape of the metal ion adsorption isotherms. The use of aminoethanoic acid as a modifying agent has been determined to strongly alter the shape of metal ion adsorption isotherms, which is due to different composition of functional groups on the sample surface and changes in the sorbent-sorbate interaction type. Using the Langmuir model and a modified Dubinin-Radushkevich equation for ion adsorption, the main adsorption characteristics were calculated. It is assumed that for the initial sorbent and the sample treated with sulphuric acid, as well as for the samples modified with aminoethanoic acid, in the case of low equilibrium iron concentration, adsorption proceeds via ion exchange. At higher equilibrium concentrations, the formation of iron ion complexes with the modifier is possible for the sorbents treated with the amino acid. It is established that the most promising sample for use as a sorbent for extracting iron ions from groundwater is the carbon material modified with both sulphuric and aminoethanoic acids (by sequential impregnation), which demonstrates the highest adsorption capacity.
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