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Biosorption of heavy metals from leachates
generated at mine waste disposal sites In
the present paper, the efficiency of adsorbents and biosorbents for the removal of metal
ions and the clean up of leachates, generated at two Romanian mine waste disposal sites is
examined. Several adsorbents such as activated charcoal, molecular sieve, shell sand,
diatomite, bentonite, kaolin, as well as biosorbents such as xanthan biopolymer and waste
biomasses are assessed, in terms of metal ion removal efficiency, in laboratory glass
columns, comprising layers of coarse sand and 3 layers of each adsorbent/biosorbent. The
effect of immobilized bacterial cells (naturally occurring consortia of acidophilic
heterotrophic and chemolithotrophic bacteria) was also studied. The experimental results
show that shell sand, molecular sieve and waste biomass have a relatively high efficiency
in removing most heavy metal ions present in low pH leachates. Regarding shell sand and
for the experimental conditions used, the selectivity follows the order
Pb>As>Cd>Ni>Cu>Zn>Al>Co>Mn. From the two types of the isolated
from leachates inoculum used as immobilized biomass, only heterothrophic acidophilic
bacteria had a positive effect on metal uptake in contrary to chemolithotrophic
acidophilic bacteria. The sufficient metal removal efficiency attained even without the
use of immobilized bacteria, is mainly due to the stimulation of naturally occurring
microbiota by addition of culture media; this stimulation may be considered as a feasible
alternative to the use of immobilized cells in biosorption applications, regardless of the
type of adsorbent/biosorbent used and the metal ion in concern. |
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