Competitive adsorption of methyl orange and ethyl orange by AB-8 resin Available to Purchase

Electrostatic attraction and hydrophobic interaction play important roles in the competitive adsorption of dyes. pH and ionic strength are two major factors that affect the competitive adsorption of dyes. Therefore, in this paper, the influences of pH and ionic strength on the competitive adsorption of dyes by AB-8 resin were studied comprehensively. Methyl orange (MO) and ethyl orange (EO) were selected as models of dye molecules. EO has only two methylenes more than MO, which makes it facile to analyze the effect of pH and ionic strength on the competitive adsorption of these dyes. The influence of pH and ionic strength on the hydrophobic interaction between the adsorbent and adsorbate and the electrostatic and hydrophobic interactions in the adsorbates themselves were studied at pH = 2, 7, and 12. The results indicated the importance of hydrophobic interaction in dye separation. Ionic strength has less effect on the adsorption capacity, being separate for zwitterions in both one-dye-component and two-dye-component systems. The difference in hydrophobic interaction increases with increasing ionic strength in a competitive adsorption system.