Title: Adsorption of chromium compounds by natural and waste mineral materials
Principal Investigator: Tomasz Bajda
Funding agency: KBN (Poland)
Project ID: 3 T09C 088 19
The aim of the project was to determine and compare the adsorption capacity of chromium compounds by various types of natural and waste mineral resources occurring in Poland, such as bog iron ore, peat, kaolin, smectite-zeolite shale, smectite clays and fly ash after burning lignite. Determinations of the most important indicators of the adsorptive capacity of potential adsorbents, such as their specific surface area, ion exchange capacity (cations and anions) and the zero point of charge were carried out. The obtained results indicate a significant differentiation of sorbents in terms of these properties.
As part of the sorption capacity assessment, the following tests were carried out:
1. The sorptive abilities of chromium compounds were compared by the tested raw materials depending on its form (Cr(VI), Cr(III)), concentrations in which it occurs, and the pH of the reaction medium. The adsorption isotherms Cr(VI) and Cr(III) were determined, and the effect of pH on the sorption was examined.
2. The reduction of Cr(VI) to Cr(III) was investigated as a result of the reaction of anionic chromium forms with surface of sorbents.
3. The stability of connections of adsorbed chromium compounds, i.e. grade, was evaluated desorption.
4. The influence of time on the sorption kinetics of Cr(III) and Cr(VI) and reduction of Cr(VI) to Cr(III) was investigated.
5. The adsorption competitiveness effect of anions for Cr(VI) was investigated.
6. The mechanism of sorption, i.e. the contribution of physical sorption (nonspecific), was investigated, chemisorption (specific sorption) and ion exchange as a result of the reaction of chromium ions with surface of adsorbents.
The results of the experiments performed generally indicate that the best sorbents of chromium (III) are peat and fly ash, and slightly worse bog iron ore, smectite ore and smectite-zeolite claystone. In contrast, sorption of chromium (VI) is best for bog iron ore and peat, slightly less fly ash, while other raw materials have very low sorption capacity Cr(VI). To identify the anionic forms of Cr(VI) formed on the surface of the adsorbent, infrared (IR) spectroscopy was used. The presence of additional bands indicating the creation of new complexes between the chromate anions and cations included in the sample was found. Thus, the nature of the reaction between chromium ions and the adsorbent surface (specific sorption) was proposed.
Most important publications:
- Kłapyta Z., Manecki A., Krzyżanowski A., Bajda T. 1999. Sorption properties of smectite-clinoptilolite shales of the Outer Flysh Carpathians (Poland). Conference of The European Clay Groups Association, Euroclay’99, Kraków, 5-9 September 1999. In: Book of abstracts, 102.
- Bajda T., Franus W., Manecki M. 2000. Sorption of selected heavy metals (Cr(III), Cu(II), Pb(II)) on smectite-clinoptilolite shales of the Outer Flysh Carpathians (Poland). International Conference Minerals of the Carpathians, Miskolc (Hungary), 9-10 March 2000. In: Acta Miner. Petr. Szeged, 41, Supl. A, 10.
- Franus W., Bajda T., Manecki M. 2000. Potential use of clinoptilolite-smectite claystones from the Outer Flysh Carpathians (Poland) for remediation. EMU School meeting: Environmental Mineralogy, Budapest, May 18-19, 2000. In: Acta Miner. Petr. Szeged, 41, Supl. B, 26.
- Bajda T. 2001. Adsorption of chromium compounds on various mineral raw materials. 15th International Symposium on Environmental Biogeochemistry, Wroclaw, Poland, September 11-15, 2001. In: Biogeochemical Processes and Cycling of Elements in the Environment. Weber J., Jamroz E., Drozd J., Karczewska A (ed), 281-282.
- Bajda T. 2001. Adsorption of chromate on various geological materials. Konferencia Doktorandov a Mladých Vedeckých Pracovníkov, Herlany (Slovakia), 23-24 April 2001. In: Mineralia Slov., 33(1), Geovestnik, 9-10.
- Bajda T., Krajewski M. 2001. Geochemical, mineralogical and petrological diversification of Upper Jurassic limestones of the Zakrzówek horst, Kraków region, southern Poland. Konferencia Doktorandov a Mladých Vedeckých Pracovníkov, Herlany (Slovakia), 23-24 April 2001. In: Mineralia Slov., 33(1), Geovestnik, 10.