Determination And Investigations On Adsorption
DETERMINATION AND INVESTIGATIONS ON ADSORPTION
OF SELECTED INORGANIC CATIONS AND ANIONS WITH
THE UTILIZATION OF ACTIVE CARBON ADSORBENTS
A. Gierak, R. Leboda, B. Charmas, J. Skubiszewska-Zieba
Faculty of Chemistry, Maria Curie-Sklodowska University,
2-031 Lublin, Poland e-mail: gierak@hermes.umcs.lublin.pl
Investigations on adsorption inorganic cations and anions from aqueous solutions are very important problem from the theoretical and practical point of view. This is connected with the problem of concentrations these ions before these analysis and investigations on removing them from different matrices (i.e. sea water, blood, physiological liquids).
In this paper there are present results of investigations on adsorption selected inorganic cations (Fe3+, Pb2+, Ni2+, Co2+, Cd2+ and Zn2+) and anions (Сl-, Вг-, J-, NO2-, NO3-, SCN- SO42-, C2O42-, CrO42-) from aqueous solutions on carbon adsorbents with different surface properties. As a initial material active carbon from HZSDD Hajnowka (GRYFSKAND at present time) were chosen. These adsorbents were prepared by different physic-chemical methods to change its adsorption properties. Initial adsorbent used to this investigations were oxidized with nitrate acid (HNO3), hydrogen peroxide (H2O2) and by heating in air atmosphere (at 300°C). Another parts of carbon adsorbent were heated in hydrogen atmosphere at 800°C, and hydrothermally modified in steam atmosphere (in temperature range 800 - 900°C). This modification leads to change structural and surface properties of initial carbon adsorbent, i.e. change its surface area, pore volume and amount of polar functional group on its surface.
The determination of cations and anions presented in water matrix at very low concentration (μg/dm3 - ppb) is a difficult problem of environmental analysis. One of the method preparation of cation and anions samples to analysis by AAS or IC HPLC at very low concentration is their preconcentration using solid phase extraction method (SPE). Among typical ion exchange materials up till now used interesting and important from practical point of view is investigation on application carbon adsorbents to this
aim. Carbon adsorbents possesses adsorption as well as ion exchange properties.
The measurements of cations concentration were performed by means of atomic absorption spectroscopy (AAS) and UV-VIS absorption spectroscopy, whereas determination of concentration of inorganic anions in water were performed by ion chromatography (IC).
Analysis of adsorption isotherms of inorganic cations on modified active carbons suggests, that adsorption process is determined either by the type of sorbed ions, pH solution and the nature of carbon adsorbent surface or by the presence of other ions in aqueous solution.
Solid phase extraction technique (SPE) was applied to checking the concentration efficiency of cations and anions on carbon adsorbent. Using SPE column packed with carbon adsorbent and atomic absorption spectroscopy (AAS) or ion chromatography (IC) it has demonstrated the possibility of determination of low concentration of separated ions (below 1g/m3) in aqueous solutions.
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