Effects of the conformation of polyacrylic acid on the dispersion-flocculation of alumina and kaolinite fines

Abstract

Conformational characteristics of polyacrylic acid (PAA) adsorbed on alumina were studied along with stability of its suspension in order to delineate the mechanism by which polymer conformation affects the stability of fines. Fluorescence spectroscopy, with pyrene as the probe, was used to monitor the conformation of the polymer at the solid-liquid interface. The stability of these fines with PAA in coiled, stretched and coiled-transformed-to-stretched conformations was investigated. With PAA in coiled and stretched forms, the suspensions were slightly flocculated. Under the coiled-to-stretched conditions, achieved through manipulation of polymer conformation, flocculation was drastically enhanced at lower polymer concentrations, while a stable dispersion was observed at higher polymer concentrations. This difference in dispersion-flocculation behavior is explained on the basis of a concentration-dependent conformational transition. Enhanced flocculation of kaolinite was also achieved by manipulation of polymer conformation.