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SORBENTS OF HEAVY METALS BASED ON COMBINATION OF LOW RANK COALS AND CHITOSAN

AUTHOR/S: J. MIZERA, M. HAVELCOVA, VL. MACHOVIC, L. BORECKA, I. KRAUSOVA
Sunday 1 August 2010 by Libadmin2010

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 2, 781-786 pp

ABSTRACT

The study has been aimed at development of cheap sorbents of toxic heavy metals and
radionuclides based on low rank, low energetic coals in combination with chitosan for
use in treatment of both waste and drinking water and construction of active
geochemical barriers. Sorbents based on lignite and naturally oxidized lignite
(oxihumolite, leonardite) were prepared, both raw and impregnated with chitosan from
its solution in oxalic acid. The sorbents were characterized by chemical and structural
analyses. Their sorption performance for Co, Cu, and Cd was tested in equilibrium
sorption experiments with respect to pH and metal concentration. The sorption
efficiencies were calculated from the amount of metal retained by the sorbent, which
was determined by instrumental neutron activation analysis in the short time irradiation
mode with epithermal neutrons (in a Cd shielding). For pH 5, sorption isotherms were
determined and fitted using the Langmuir-Freundlich model. Although chitosan
provides only surface coating of the coal sorbents, its presence has affected significantly
their sorption performance. At identical pH values, the sorption efficiencies of the
chitosan coated coals were higher than those of the raw coals for Co and Cd, and this
difference was increasing with pH. For Cu, the effect was ambiguous and rather reverse.
The chitosan coating may stabilize coal in basic solution and inhibits leaching of humic
substances and their complexes with the metals from coal into solution. Besides fixing
metal humates within the sorbents, chitosan may positively affect the sorption efficiency
also by its buffering action against the hydroxide addition.

Keywords: low rank coal, chitosan, heavy metals, sorption