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Abstract

Densification of oil sand tailings deposited in the tailing ponds and recovering water from them are two major challenges issues in the oil sands surface mining industry. A small increase in the tailing settlement rate (which normally is very slow) can improve the densification of tailings and significantly, reduce water consumption and the volume of tailing ponds. Currently most of the industrial methods for consolidation of oil sand tailings are based on clay particle flocculation methods which use different kinds of agents such as calcium sulfate (gypsum), and polymeric flocculants. In this work, rhamnolipid (JBR 425) was investigated as a flocculating agent and microbial activities by performing the sedimentation experiments to increase the sedimentation of fine tailing particles. It has been found that rhamnolipid increased sedimentation by improving the hydrophobic interaction between the particles. The feasibility of in situ biosurfactant production by indigenous microorganisms, Bacillus subtilis strain and two microbial strains isolated from weathered oil was investigated and it was found that all strains could produce very low amounts of biosurfactant. A mixed culture of two microbial strains isolated from weathered oil increased the sedimentation. Different concentrations of rhamnolipid together with these two microbial strains at 23 ºC ºC could lead to significant increases in sedimentation (by a maximum factor of 3.04), increases in the concentration of larger particles (by a maximum factor of 1.9), particle mean diameter (by a maximum factor of 2.11) and flocculation in the tailings samples amended with them compared to the control. Rhamnolipid (0.5%) together with these two microbial strains at 15 ºC ºC showed significant increases in
sedimentation (by a factor of 5.1), the concentration of larger particles (by a factor of 2.63),
particle mean diameter (by a factor of 2.70) and flocculation in the tailings samples compared to
the control. while the zeta potential is still negative. According to the pH measurements (during
the 50 days) increase in the ionic strength (I) of the pore water and reduction in the thickness of
the DDL of clay particles is not responsible for increasing the sedimentation as dissolution of
MFT carbonate minerals and releasing divalent cations could not occur at pH higher than 7.5.
However there might be a small amount of CH4 production at 15 ºC oC in the deeper layer of
mud. This means that the mechanism of flocculation in these cases could be probably due to
increasing the hydrophobicity of the particles, due to the interaction of biosurfactant and high
molecular weight microbial organic compounds through a bridging mechanism with clay
particles, and to due to forming transient canals from small amounts of CH4 production. Using
rhamnolipid as a flocculating agent could bring the remaining oil and also a small amount of
insoluble heavy metals from the tailing sediment into the water. Dissolved heavy metal ions and
rhamnolipid in water could be removed through micellar- enhanced ultrafiltration (MEUF)
process (between 30% for Cd and 100% for V, and 97.5% for rhamnolipid). This work shows the
potential of using rhamnolipid and microbial culture in order to increase the oil sand
sedimentation through flocculation and microbial activity in a more environmental friendly and
densification process.

Available Versions of this Item

• Application of Rhamnolipid and Microbial Activities for Improving the Sedimentation of Oil Sand Tailings. (deposited 16 Jun 2016 15:25)
  • Application of Rhamnolipid and Microbial Activities for Improving the Sedimentation of Oil Sand Tailings. (deposited 27 Oct 2022 13:46) [Currently Displayed]
  • Application of Rhamnolipid and Microbial Activities for Improving the Sedimentation of Oil Sand Tailings. (deposited 27 Oct 2022 13:46)