STUDY OF Cu(II) ADSORPTION BY BENTONITE AND FOLLOWING REGENERATION BY BIOLEACHING

Abstract

The natural bentonite and bentonite/iron oxide composite were used as sorbents of Cu(II). Their
sorption properties were examined under the different conditions such as pH of the solution, initial
metal ion concentration. The bentonite removed 71 % Cu(II) while composite 90 %. Their maximum
adsorption capacities were 34.1 and 44.4 mg Cu(II) g-1, respectively. The chemical regeneration of
composite sorbent by organic acids (oxalic, citric) led to partial Cu(II) dissolution. The hydrochloric
acid caused its structural destruction. For the bacterial regeneration, the sorbents were inoculated with
heterotrophic indigenous bacteria. After 10 days the bacteria released approximately 80 % of loaded
Cu(II), leaving the sorbents stable. Longer treatment and higher concentration of metal cations caused
the reverse sorption of Cu(II) by bacteria. The regenerated sorbent was successfully repeatedly used for
the Cu(II) adsorption.