The effectiveness of the water-soluble starch xanthate (SSX) process for re
moval of heavy metals [Hg(II), Cu(II), Cd(II) and Ni(II)] has been evaluate
d. Removal of Hg(II) and Cu(II) is effective; Cd(II) and Ni(II), less so. T
he metal [Hg(II)/Cu(II)] binding capacity remains the same in the pH range
3-7. An optimum metal/SSX ratio is observed for maximum metal removal. The
metal removal efficiency of SSX appears to be dependent on a specific chemi
cal interaction between metal and SSX and on separation of the metal-xantha
te complex from the aqueous phase. An analogy between the metal-SSX system
and the colloid-cationic polyelectrolyte system (coagulation and flocculati
on in water treatment) is observed. The role of ionic strength for metal-SS
X system appears to be analogous to the role of indifferent electrolyte in
coagulation and flocculation. (C) 1999 John Wiley & Sons, Inc.