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

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.