chapter  17
22 Pages

1Chapter 7 Interactions of Polyelectrolytes with Particulate Matter in Aqueous Systems

Coagulation and occulation are key unit operations in water treatment as ef ciency of subsequent clari cation and ltration steps is linked critically with the manner, effectiveness, and rate of occulation [4,5]. Polymers and polyelectrolytes have become favorable occulation and ltration aids in water treatment due to several reasons [6]. For example, the required polymer dosage is relatively lower than that for the commonly employed inorganic coagulant, alum. The resultant sludge generated is also relatively low and the concentrations of dissolved inorganics such as aluminum in treated water are minimal. The strength of ocs obtained through polymer-induced occulation is also high because polymeric occulants provide many links between particles due to the attachment of a number of segments with surface groups on particles. Moreover, it is not always possible to control the stability of colloidal suspensions ef ciently and obtain the desired

17.1 Introduction ....................................................................................................................... 343 17.2 Characteristics of Particulate Matter and Polyelectrolytes ...............................................344 17.3 Polymer Adsorption .......................................................................................................... 345 17.4 Polymer-Induced occulation ...........................................................................................348 17.5 Modeling of Polymer Adsorption, Interaction Forces, and Flocculation ......................... 352 17.5.1 Polymer Adsorption ............................................................................................. 353 17.5.2 Interaction Forces between Polymer-Covered Particles ...................................... 353 17.5.3 Polymer-Induced Flocculation ............................................................................. 354 17.6 Summary and Suggestions for Future Research ............................................................... 359 Acknowledgments ..........................................................................................................................360 References ......................................................................................................................................360