Effect of Electrolyte Concentration in Process Water on Flocculation


  • Jose Moreno-Chavez Escuela Superior Politecnica del Litoral




Coagulation, Flocculation, Electrolyte solutions, Intrinsic viscosity


Abstract. The effect of electrolyte concentration and potential determining ions on the coagulation and flocculation of illite, dolomite, and illite-dolomite mixture suspensions was investigated. Electrokinetic measurements, settling rate tests, and viscosity measurements were performed to examine the stability of these mineral suspensions and    to characterize flocculants under various physico-chemical conditions. Two flocculants: A-100 anionic polyacrylamide (PAM) and polyethylene oxide (PEO) were employed.

The tests revealed that polyethylene oxide does not flocculate dolomite under any tested conditions. Viscosity results corroborated that the conformation of PAM macro- molecules in water is very sensitive to electrolyte concentration; on the other hand, the conformational state of PEO macromolecules is not affected by ionic strength. The intrinsic viscosity measurements suggest that the unattainable flocculation of dolomite suspensions with PEO must result from poor adsorption of this flocculant onto dolomite particles.  In both tested cases, with PAM and PEO, the relationship between coagulation and flocculation was not confirmed.


Resumen.  Se investigó el efecto de la concentración electrolítica y iones determinantes de potencial en la coagulación y floculación de suspensiones de ilita, dolomita y mezcla de ilita-dolomita. Mediciones electrocinéticas, ensayos de velocidad de sedimentación, y mediciones de viscosidad fueron realizadas para examinar la estabilidad de estas suspensiones minerales y caracterizar floculantes bajo varias condiciones fisicoquímicas. Se empleó dos floculantes: A-100 poliacrilamida aniónica (PAM) y óxido de polietileno (PEO).

Los experimentos revelaron que el óxido de polietileno no flocula la dolomita bajo ninguna condición empleada. Los resultados de viscosidad corroboraron que la conformación de las macromoléculas PAM en agua es sensible a la concentración electrolítica; por otro lado, el estado conformacional de las macromoléculas de PEO no se ve afectado por la fuerza iónica. Las mediciones de viscosidad intrínseca sugieren que la floculación inalcanzable de las suspensiones de dolomita con PEO debe ser resultado de una mala adsorción de este floculante en las partículas de dolomita. En ambos casos probados, con PAM y PEO, no se confirmó la relación entre coagulación y floculación.


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