Effect of pH on the Flocculation of SDS Micelles by Al 3+

Abstract

SDS micelles flocculate in the presence of Al3+, creating an aggregate with pollutant-removing properties. The fraction of SDS micelles flocculating depends on the concentrations of SDS and Al3+. This paper describes how this fraction also changes with pH. There are two reasons for this dependence: a change in pH has a strong effect in the solution chemistry of Al3+, converting it into the compound [Al13O4(OH)24]7+, a strong flocculant, or precipitating it as Al(OH)3; and at low pH protons may compete with Al3+ as binding counter-ions for micelles. An increase in pH allows flocculation of SDS at high concentrations of Al3+, which under unmodified pH does not occur. Micelle flocculates are reported in this work to exist between pH 5 and pH 8, suggesting the potential use of Adsorptive Micellar Flocculation for the removal of anionic pollutants from waste waters not necessarily limited to acidic solutions.