Removal studies of Cr2O3 colloidal particles using cationic poly(l-lysine) and its block copolymers with poly(ethylene glycol)

Abstract

Cr2O3 dispersions are considered to be dangerous for aqueous ecosystems and for this reason it is necessary to develop methods allowing solid particles separation.Structure of the adsorption layer formed at the solid surface determines the colloidal suspension stability. Moreover, in the case of ionic polymers the solution pH considerably affects the chains arrangement. Hence, the influence of cationic poly(l-lysine) and its copolymers adsorption on the chromium(III) oxide (Cr2O3) particles stability was investigated. Although the analyzed substances are characterized by the similar average molecular weight, they exhibit various macromolecular structures resulting from the different PEG and polyamino acid length ratios. The sample's stability was examined by the use of the turbidimetric method enabling the Turbiscan Stability Index (TSI) parameter calculation.As one can see, solid suspensions without the tested polymers are relatively unstable. At pH 4, introduction of the cationic macromolecules causes the increase in the sample stability. This can be explained by the electrostatic repulsion between the totally ionized polymeric chains adsorbed on the adjacent Cr2O3 particles. At pHpzc, changes in the TSI values are related to the different polymer chain arrangements.