Environmental Engineering FOURTH EDITION

138 ENVIRONMENTAL ENGINEERING

Slipping plane (B)

I

I. I

' repulsion, R

P

attraction. A

I.

Figure 7-3. Reduction of the net charge on a particle as a result of the addition of

trivalent counterions. (A) Particle carries net negative charge and van der Waals positive

charge; energy barrier prevents coagulation. (B) Addition of trivalent cations reduces

energy barrier, and coagulation is possible.