Adsorption of organic–inorganic hybrid polymers on kaolin from aqueous solutions

Abstract

Adsorption of two in-house synthesized organic-inorganic hybrid polymers, Al(OH)3-polyacrylamide (Al-PAM) and Fe(OH)3-polyacrylamide (Fe-PAM) on kaolin and corresponding flocculation of fluid fine kaolin suspensions were investigated. For comparison, a commercial anionic flocculant (partially hydrolyzed polyacrylamide or known as H-PAM) was also examined. The flocculation dynamics of fine kaolin suspensions were determined using an on-line focused beam reflectance measurement (FBRM) probe. As an example of applications, flocculation of a laboratory oil sands extraction tailings sample was studied. A quartz crystal microbalance with dissipation (QCM-D) was used to determine adsorption kinetics of the polymers on silica and alumina as representative of T- and O-basal planes of kaolin.Al-PAM, Fe-PAM and H-PAM were shown to be excellent flocculant of kaolin suspensions, with H-PAM being less effective and more sensitive to overdosing. The flocculation performance was greatly influenced by proper mixing. Strong flocculation of kaolin suspension by Al-PAM and Fe-PAM is attributed to their ability to adsorb on both basal planes of kaolin, in contrast to relatively weak flocculation of kaolin by H-PAM which adsorbs only on positively charged aluminum oxy-hydroxyl basal planes. The electrostatic attraction or repulsion is identified as a critical parameter in determining polymer adsorption and hence corresponding flocculation of kaolin suspensions.