Effect of UV light irradiation, pH and concentration on the dye sequestration efficiency of anionic surfactant based self-assembled aqueous mesophases

Abstract

Lyotropic lamellar phases are prepared by using the varying concentration of sodium dodecyl sulfate: water (SDS: W) and then doped with methyl blue dye (0.01 wt.%). Textural analysis confirms that the addition of the dye does not perturb the lamellar patterns. Dye molecules may self-assembled over the lamellar aqueous interface in an ordered fashion. Lyotropic lamellar phases are explored for methyl blue sequestration/adsorption under the influence of UV irradiation (125 W and λ=365 nm). No structural phase change in lyotropic systems has been observed after UV irradiation. However, visual blue to colourless transition and continuous suppression of adsorption intensity has been seen for the dye-doped system. About 97–99% sequestration efficiency is noted for these lyotropic systems within 60 min in alkaline pH (8–9). Sequestration/ adsorption of dye could be the result of electrostatic interactions amidst N+ and O− of dye and anionic surfactant SDS. Such interactions alter one of the double bonds of one NH group of methyl blue permanently, hence, disrupts the molecular planarity of the dye molecule and could be a cause of dye sequestration. The effect of varying pH has also been discussed. Studied systems could be seen as an economic and efficient adsorbent for water and impurity purification applications.