Adsorption of the Cationic Dye Methylene Blue on Anodic Porous Alumina in Sodium Dodecyl Sulfate Solutions.

Abstract

Dyeing of anodic porous alumina (APA) prepared by aluminum anodization is generally achieved by dipping the positively charged APA surface into a negatively charged dye solution. We have proposed a new method to adsorb dyes and molecules onto APA using negatively charged sodium dodecyl sulfate (SDS). In this study, we found that cationic methylene blue (MB) can be adsorbed onto the positively charged APA surface using SDS aqueous solutions. We investigated two adsorption methods: dipping APA into aqueous solutions containing both MB and SDS (method 1) and successive dipping of APA into SDS and then MB aqueous solutions (method 2). The two methods produced different adsorption characteristics. Method 1 adsorption profile reflected formation of dye-rich induced micelles below the critical micellar concentration (CMC) and electrostatic interaction of micelles with MB above CMC. Method 2 adsorption was explained by electrostatic interaction of preadsorbed SDS with APA and MB.