Adsorption of poly(styrenesulfonate) onto different-sized alumina particles: characteristics and mechanisms

We report the adsorption characteristics and mechanisms of a strong polyanion, poly(styrenesulfonate), PSS, onto α-Al 2 O 3 with large size (L-Al 2 O 3 ) and small size (S-Al 2 O 3 ) in this paper. Some effective conditions to the adsorption of PSS onto L-Al 2 O 3 and S-Al 2 O 3 such as adsorption time, pH, mass ratio of PSS to α-Al 2 O 3 , and ionic strength were systematically studied. Maximum adsorption capacities of PSS onto both L-Al 2 O 3 and S-Al 2 O 3 were achieved with adsorption time 120 min, mass ratio of PSS to α-Al 2 O 3 20 mg/g, and ionic strength 50 mM NaCl. The PSS adsorption onto S-Al 2 O 3 significantly decreased with increasing pH from 4 to 9 while PSS adsorption onto L-Al 2 O 3 decreased insignificantly in the pH range 4–9. Adsorption of PSS onto both L-Al 2 O 3 and S-Al 2 O 3 increased with increasing salt from 0 to 50 mM NaCl, indicating that electrostatic and none-lectrostatic interactions controlled adsorption at low ionic strength. However, adsorption of PSS was independent on the ionic strength at salt concentration higher than 50 mM. The changes in surface charge after PSS adsorption onto L-Al 2 O 3 and S-Al 2 O 3 were determined by zeta potential while the differences of surface functional groups before and after PSS adsorption were characterized by Fourier-transform infrared spectroscopy (FT-IR). The zeta potential as a function of the mass ratio of PSS to L-Al 2 O 3 and S-Al 2 O 3 agreed well with the adsorption capacity against the mass ratio. Adsorption mechanisms of PSS onto L-Al 2 O 3 and S-Al 2 O 3 were also discussed based on the changes in zeta potential, the differences of surface functional groups, and adsorbed amount as a function of the mass ratio of PSS to α-Al 2 O 3 . [Figure not available: see fulltext.]. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.