Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface

[摘要] Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto largeα-Al2O3beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface ofα-Al2O3decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms ontoα-Al2O3at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS ontoα-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake ontoα-Al2O3in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.

[学科分类] 物理化学和理论化学