Influence of polymeric auxiliaries on particle adhesion in quaeous systems

Abstract

Turbidity is usually removed in water treatment by flocculation (followed by sedimentation or flotation) and/or deep bed filtration. To improve the removal efficiency polymeric auxiliaries are often used. It has been examined how these polymers effect the adhesion behavior of particles. The tested polymers differ in charge character, charge density and molecular weight. Experimental results point out that the adsorbability as well as the strengthening of adhesion force of polymer are considerably influenced by its electrostatic interaction with the particle surface. But there is no direct interdependence between adsorbability and strengthening of adhesion. Experiments show that besides the influence of the polymer properties there is a strong dependence on the particle contact time. The influence of the contact time is attributed to rearrangement processes of the polymer in the particle contact area and can be described as a first order reaction. The average particle adhesion force at the respective contact time is used as a measure for the actual polymer configuration in the adhesion area. The reaction velocity for the rarrangement is dependent on various parameters. It increases with rising polymer loading and decreasing molecular weight of polymer. In addition, the reaction takes place five-fold qucker in the case of preloading only one adhesion partner before contact instead of preloading both adhesion partners. Furthermore, the rearrangement of the polymer is dependent on the kind of polyer. Stronger interactions between polymer and adhesion partner cause stronger and longer lasting rearrangements than do weaker interactions. for the case of deep bed filtration it can be demonstrated that consequent transfer of the knowledge which has been established by fundamental examinations can optimize the use of polymer.