Adsorption of hybrid polyacrylamides on anisotropic kaolinite surfaces: Effect of polymer characteristics and solution properties

Abstract

Abstract Adsorption kinetics of organic-inorganic (hybrid) Al(OH) 3 -polyacrylamide (Al-PAM) with different molecular weights (for organic characteristics) and contents of aluminum hydroxide nanoparticles (for inorganic characteristics) on kaolinite basal planes was studied using a versatile quartz crystal microbalance with dissipation (QCM-D). The flocculation dynamics of kaolinite by Al-PAMs was assessed by measuring the initial settling rate of flocculated kaolinite particles and the turbidity of the supernatant after settling of flocculated solids. The areal mass (mg/m 2 ) of Al-PAMs adsorbed on tetrahedral silica and octahedral alumina basal planes of kaolinite increased with increasing molecular weight of the polymer. Increasing the content of Aluminum hydroxide nanoparticle in Al-PAM has resulted in an increase of the amount of the polymer adsorbed on silica basal planes while opposite trend was found on alumina basal planes. Results obtained from the adsorption kinetics study of Al-PAM 6R ( M w = 2.2 million Dalton, 0.11 wt% Aluminum) on silica basal planes revealed that the early stage of adsorption is diffusion-controlled. Thus, initially the adsorption rate increased with increasing temperature while the maximum coverage decreased. Moreover, the adsorption of Al-PAMs on silica basal planes was shown to decrease significantly in plant recycle (process) water compared to deionized water. Al-PAMs of higher molecular weight and/or high content of inorganic Al (OH) 3 nanoparticles were found to be more effective in flocculating kaolinite as indicated by the faster settling rates and clearer supernatant.