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| Kaduková J., Komorová T. |
| SILVER BIOACCUMULATION AND BIOSORPTION BY ALGA CHLORELLA KESSLERI FROM MODEL SOLUTIONS |
Abstract
Biological methods for wastewater treatment are becoming more accepted over the word as well as in our country. The method which makes use of accumulating abilities of living cells is called bioaccumulation. In contrast with it, biosorption uses abilities of dry or dead cells, which is technologically advantageous.
The difference between bioaccumulation and biosorption of silver from model solutions was studied in this work. From comparison of equilibrium sorption values by living cells (q = 2,83 mg/g, only 15 % drop of silver concentration) and by dry cells (q = 12,83 mg/g, 40 % loss of silver ions from solution) it is obvious that utilization of dry cells is more suitable. Silver presence on surface of algal cells (living and dry) was proven by EDX analysis. Influence of silver ions on cell surfaces was evaluated by means of electron microscope photographies. If dry cells are used in process (biosorption) there is no cell surface damage present, as suggested by electron scanning microscope photos. Biosorbent can be used repeatedly. The possibility of desorption is another advantage of biosorption process, thus, metal can be removed from cells by washing with suitable desorption agent. Damage on the surfaces of living cells is visible as crateriform cavities. Silver accumulates in cell wall and/or cell interior in the form of electron-dense round precipitates, which are better visible in living cells. The precipitates are probably formed by some bioprecipitation mechanism although in case of dry cells silver is captured also by the other mechanisms, because obseved sorption by dry cells was higher than bioaccumulation by living cells (q = 2,83 mg/g in living cells, while at the same initial concentration of silver dry cells sorption was q = 12,074 mg/g).
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| Keywords: bioaccumulation|biosorption|Chlorella kessleri|silver| |
| No 2 (2002), p. 117-123 |
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