The comparative studies on the ability of anionic surfactants to bind lead(II) ions

Abstract

Both heavy metals and surfactants are considered as environmental pollutants, however, the unique interfacial properties of surfactants determine their frequent applications in various processes dedicated to the removal of xenobiotics including metal ions from the contaminated water and soil. Therefore the studies on the effect of metal ions on surfactants properties are of great importance to gain insight into the interactions between these chemicals both in natural environment and during purification processes. The aim of this work was to verify the effect of lead(II) ions on the aggregation of the anionic surfactants: sodium dodecyl sulfate (SDS), N-Lauroylsarcosine sodium salt (Sarkosyl) and Sodium dodecylbenzenesulfonate (SDBS) and to compare the ability of these surfactants to bind these metal ions. The experiments involved electrical conductance measurements of surfactant solutions containing lead(II) ions in various concentrations, pH measurements, potentiometric experiments and the flame atomic absorption spectrometry (FAAS). The analysis of the calculated aggregation parameters and association constants as well as FAAS experiments results evidenced that among the studied surfactants SDS is of the highest, while SDBS of the lowest lead(II) ions binding ability. However, all the investigated compounds at the concentrations lower than Critical Micelle Concentration (CMC) form insoluble complexes with these metal ions. The precipitates differ in their stability, namely they dissolve at the excess of surfactant, however, for SDS this process starts at higher surfactant level as in the case of SDBS and Sarkosyl. Moreover, binding of lead(II) ions to the negatively charged surfactant micelles is the most effective in the case of SDS and the weakest for SDBS.