Study of Al(OH)3−Polyacrylamide-Induced Pelleting Flocculation by Single Molecule Force Spectroscopy

A nanocomposite polymer, Al(OH)3-polyacrylamide (Al-PAM) hybrid, was tested as a flocculant. This novel hybrid polymer was found to induce pellet-like floccules, leading to a more effective solid-liquid separation than common polyacrylamide (PAM)-based flocculants. To understand the mechanism of Al-PAM-induced pelleting flocculation, the molecular structure of this hybrid polymer was studied using an atomic force microscope (AFM). The interactions between Al-PAM molecules and a silica surface were measured using single molecule force spectroscopy (SMFS). The Al-PAM molecules were found to have a star-like structure with Al(OH)3 colloidal particles as cores connecting PAM chains. The SMFS results showed a strong attachment of the Al(OH)3 cores to the silica surface with an adhesion force of approximately 1250 pN, in contrast to a weaker adhesion force of only approximately 250 pN for PAM chains on the silica surface. The Al-PAM-induced pelleting flocculation is attributed to its star-like structure.