The Use Of Extraction Methods For Recovering Metals And Carriers From Used Carbon Sorbents And Catalysts
THE USE OF EXTRACTION METHODS FOR RECOVERING METALS AND CARRIERS FROM USED CARBON SORBENTS AND CATALYSTS
E. Bezak-Mazur1, L. Dabek1, M. Repelewicz2, A. Swiatkowski3
1The Swietokrzyskie University of Technology,
2The Swietokrzyskie Academy,
3The Military Academy of Technology
Wastes present one of the most crucial problems of the environment protection. It results from both the crux of the problem and the diversity of their content. Among numerous wastes there are used carbon sorbents and catalyst containing heavy metals which have been used in the industrial organic synthesis, for obtaining a substance of high purity, in the respiratory protection equipment, for reducing and oxidizing nitric oxide to nitrogen, in sewage treatment, as well as active carbons impregnated with silver compounds used as water filters.
The used carbon sorbents and catalysts containing heavy metals are valuable secondary raw materials considering their relatively high, up to several per cent of waste mass, content of metals and active carbon which can be re-used after due treatment. It is then advisable to carry out investigations on recovering both metals and carbon carriers.
Among the well-know methods of treating used carbon sorbents and catalysts, our preference stays with extraction methods as they are most favourable to the utilization of wastes of the kind and guarantee the maximum recovery of metals and carbon carriers. The methods using division phenomena occurring at the phase boundary can be used as the liquid-liquid extraction and the liquid-solid extraction. The liquid in the liquid-solid extraction can be a supercritical solvent. In practice, the use of the above-mentioned extraction methods is reduced to leaching with organic and inorganic solvents, and to the sequence extraction and the supercritical one.
The present experimental range was as follows:
– leaching metals from carbon sorbents and catalysts with inorganic solvents (nitric acid, hydrochloric acid, aqua regia, ammonium base),
– the sequence extraction (acetic acid, hydroxylamine hydrochloride, hydrogen peroxide and ammonium acetate),
– the supercritical extraction with the use of CO2,
the present investigations showed the extraction methods to be of wide use for removing metals from carbon sorbents and catalysts, but
– for recovering metals and carbon carriers from used catalysts the method combining the supercritical extraction with leaching with acid solutions is the most effective,
– for removing metals from the carbon used before in the sorption of metals from aqueous solution, leaching with acids in an effective method giving an extra effect of removing ash,
– the use of the sequence extraction gives an insight into the chemical form of the metal present in an aged or used catalyst and contributes to its recovery in a selective way.
Acknowledgement
The work done under the research project of the Research Board 3T0 9C 04617
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