Effect Of Polymer-surfactant Interaction On The Hindered Settling Of Mineral Suspension
EFFECT OF POLYMER-SURFACTANT INTERACTION ON THE HINDERED SETTLING OF MINERAL SUSPENSION
Z. Sadowski, I. Polowczyk
Department of Chemical Engineering and Heated Equipment Wroclaw University of Technology Wroclaw, Poland
This study was undertaken to investigate anionic surfactant interaction with non-ionic polymer onto the mineral surface. Poly(ethylene-oxide) PEO of MW 5.000000 and 300000 were used as a polymer, and sodium dodecylsulphate (SDS) was applicated as an anionic surfactant. The Zn-Pb fine flotation tailing used in these studies was purchased from IMN (Institute of Noniron Metals) Gliwice, Poland. The particle size distribution and surface area of flotation tailing were determined. The mineral particle had an average size of 8.50 mm and surface area equals 9.22 m2/g. The main component of the mineral suspension was dolomite CaMg(CO3)2.
The polymer and surfactant adsorption on the mineral surface was estimated from the different between an initial and receiving concentration in solution. The surfactant concentration was determined using a two-phase titration technique with Rhodamine 6G as an indicator. The polymer concentration in a solution was analysed by determining of the turbidity after addition of tannin.
The sedimentation studies were conducted using a 50 cm3 sedimentation cylinder with the vertical scale. The sedimentation velocities of different density fraction of flotation tailing with adsorbed of mixed polymer-surfactant layer were measured. The accumulation of solids at the bottom of the sedimentation column was visible, and its growth was noted.
The mechanism of interaction between sodium dodecylsulphate and polyethylene oxide at the mineral surface was similar to that in a bulk solution. The association has taken between the ether oxygen of the polymer and the head group of the anionic surfactant. The binding isotherm of SDS at the solid-liquid interface covered by PEO layer was similar in a shape to that for the bare interface. On the other hand, the presence of pre-adsorbed of surfactant layer causes a decrease of polymer adsorption. This effect is clear illustrated to
the polymer with the higher molecular weight (PEO 5.000 000). These results imply a competition adsorption.
When the mineral particles are coated by the surfactant, polymer and mixed polymer-surfactant layer, the sedimentation velocity will be depended on the flocculation and steric interactions. It was found that the adsorption of polymer molecules causes a strong flocculation of investigated suspension. Also, in the case of polymer-surfactant layer when the polymer was first adsorbed, the flocculation occurred. The mean particle diameter, calculated from Stokes equation, was twice big than it was without reagents (10.13 and 25.33 mm). These results were supported by the sediment volumes.
Our observations suggest that the steric interaction occurs in the case of SDS+PEO 300 000 mixed layer when the surfactant was adsorbed as a first. As a consequence of steric interaction the calculated of mean diameters were close to the value of mean diameter of the mineral suspension without reagents (11.91, 11.65 and 10.13 mm).
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