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Testing the efficiency of different rhamnolipid concentrations on metal removal from

tailings

Etir Chalabi

Center for talented youth Belgrade II, Belgrade etirchalabi@gmail.com
1. Introduction content determination on ICP (Inductively Coupled
Plasma).

Soils contaminated with heavy metals represent a serious
threat for environment and human health. Particularly 4. Results and discussion
dangerous are tailings and waste rocks contaminated with
As and other heavy metals because they show adverse Production of rhamnolipids by fermentation obtained yield
effects on all organisms even if present in low of 637.8 mg/L. By using thin layer chromatography on a
concentrations. Bioremediation is efficient and silica gel plate, two components in rhamnolipid mixture
economically acceptable method for dealing with this were observed, one with Rf value 0.174 for less mobile
problem. fraction of the mixture (di-rhamnolipids) and another 0.484
Rhamnolipids are anionic glycolipid biosurfactants that for more mobile fraction (mono-rhamnolipids).
have the ability to mobilize and remove metals by The resulting metal content in the sample of Bor tailings are
complexing them or by forming micelles and so increasing generally consistent with previously published [3], while
their solubility. Rhamnolipid features, such as low toxicity, significant difference was found only in Zn content where
biodegradability, the possibility of production from obtained value was greater. For most metals, the highest
renewable sources as well as the possibility of the efficiency on metal removal (Fe, Co, Cr, Zn) is obtained
production in relatively high quantities in a short period of with control, NaOH solution without rhamnolipids.
time, give them an advantage over synthetic surfactants as Exceptions are observed in As, Cu, Ni, Pb, Sr extraction.
possible agents in washing technologies of metal When it comes to different rhamnolipid concentrations, the
contaminated soils [1,2]. highest leaching levels were achieved with 0.1%
rhamnolipid solution.
2. Objective

In this study, the possible effect of different rhamnolipid
concentrations, produced by Pseudomonas aeruginosa D3
bacterial strain, on mobilization and removal of metals from
tailings was examined.

3. Material and methods Picture 1. The content of As, Fe, Cu, Pb and Mo extracted
with different rhamnolipid concentration solutions from
Rhamnolipids were produced in fermentation process by Bor tailings
Pseudomonas aeruginosa D3 strain on PPGAS medium. It
lasted 4 days on shaker at 28˚C. After separating biomass
by centrifugation, rhamnolipids were extracted from 5. Conclusion
fermentation liquid with a mixture of solvents,
chloroform:methanol (2:1, v/v). The organic extract was Fermentation with Pseudomonas aeruginosa D3 strain on
dried with anhydrous sodium sulphate and evaporated on PPGAS medium yields approximately 630 mg/L of
the vacuum evaporator. Mono- and di-rhamnolipid presence rhamnolipids. The largest metal removal is achieved with
was confirmed with thin layer chromatography on silica gel 0.1% rhamnolipid solution. Based on the results of this
plate, where mixture of solvents study, it is necessary to check the effect of NaOH without
chloroform:methanol:water (65:15:12, v/v/v) was used as a rhamnolipids as leaching solution, and to evaluate what
mobile phase for separation. In metal leaching experiment, impact solid-liquid phase ratio has on leaching efficiency.
a sample of Bor flotation tailings was used as a substrate.
Testing the efficiency of rhamnolipids on metal leaching 6. References
was done with 0.05%, 0.1% and 0.15% rhamnolipid
solution in NaOH (pH=11) and NaOH solution (pH=11) [1] M. Pacwa-Plociniczak, G.A. Plaza, Z. Piotrowska-
without rhamnolipids was used as control. Leaching Seget, S.S. Cameotra, Int. J. Mol. Sci. 12, (2011), 633
experiment was done by using batch technique where [2] A.A. Juwarkar, A. Nair, K.V. Dubey, S.K. Singh, S.
extraction process lasted during the night on shaker, with Devotta, Chemosphere 68, (2007), 1996.
solid-liquid phase ration 1:10 (w/v). The samples obtained [3] M.M. Antonijević, M.D. Dimitrijević, Z.O. Stevanović,
after leaching, as well as the sample of Bor tailings, were S.M. Serbula, G.D. Bogdanović, J. Hazard. Mater. 158
digested with HNO 3 and normalized to 50 ml for metal (2008)