Abstract:
Potentiometric titrations of quartz, kaolinite, feldspar, and partially hydrolysed polyacrylamide (HPAM), and sorption measurements of HPAM on the minerals, allows identification of the general mechanisms of polyacrylamide adsorption to aluminosilicates and quartz. Adsorption was monitored at the mineral solution interface by way of X-ray photoelectron spectroscopy (XPS). XPS spectra of the unreacted minerals show bands in the O1s, Si2p, Al2p, and C1s regions. Additional peaks are observed in the C1s and N1s regions after treatment with polyacrylamide and the latter is used in this study to monitor polymer adsorption. N1s peak intensities increase with polymer concentration to a maximum corresponding to surface site saturation. At a fixed polymer concentration, adsorption varies with pH-dependent surface charge. The adsorption mechanism changes with pH, reflecting variation in the pH-dependent concentrations of ionizable groups on polyacrylamide and at aluminosilicate surfaces, and the extent of hydrogen-bonding between uncharged mineral surface sites and polymer amide groups.