Comparison of the influence of polyaspartic acid and polylysine functional groups on the adsorption at the Cr2O3—Aqueous polymer solution interface

• Published in: Applied surface science 2014-08, Vol.311, p.734-739
• Main Authors: Ostolska, Iwona, Wiśniewska, Małgorzata
• Format: Article
• Language: English
• Subjects: Addition polymerization; Adsorption; Adsorption equilibria; Chromium; Chromium (III) oxide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Density; Determination of pKa value; Exact sciences and technology; Functional groups; Molecular weight; Physics; Polyamino acids; Potentiometric titration; Surface charge density; Surface chemistry; Titration
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.05.149

•Adsorption mechanisms of two polyamino acids on the surface of Cr2O3 was proposed.•The Gran's method was used to estimate the polyamino acids dissociation constants.•In the presence of polyamino acids the change in surface charge density was observed.•The shift of pHpzc value depend on the type of the functional groups in polymer chain. Polyamino acids are a group of synthesized polymers obtained by polymerization of a given kind of amino acid monomer. Because of high biodegradability of this class of polymers, they can be used as flocculation or stabilization agents in the environmental aspects. Therefore determination of their influence on the stability of the aqueous suspension of metal oxides is important. An influence of different functional groups of polyamino acids, their molecular weight and concentration on the adsorption at the chromium (III) oxide (Cr2O3)—aqueous solution interface was determined. Experiments were carried out for four values of solution pH varying from 3 to 10 (3, 4, 7.6 and 10, respectively). Two polymers were used: anionic polyaspartic acid (ASP) of 6800 and 27,000 as well as polylysine (LYS) of 4900 and 33,000 molecular weights. Changes of surface charge density of colloidal Cr2O3 in the presence and in the absence of macromolecular substances were determined using potentiometric titration. In these studies the influence of the concentration and molecular weight of the ionic polymers on the pHpzc value was determined. Additionally, due to the lack of appropriate literature data, potentiometric titration of the selected polymers was performed to determine pKa values.