Spectrophotometric investigation on interactions of dye with surfactant in aqueous as well as alcoholic media

Abstract

The interaction of the methyl orange (MO) dye with cetyltrimethylammonium bromide (CTAB) in propanol, butanol, and water was studied using spectrophotometry method. The NLREG approach was used to compute the distribution constant which is the lower as carbon number increases which resembles that value of distribution constant 0.07161476, 0.00060913, 0.00010865 is of water, 1-propanol, 1-butanol media respectively. The Benesi-Hilderbrand and Hashemi and Sun equations were also used to determine the binding constant (Kb) and Gibbs free energy of binding (ΔG°). As the alkyl chain lengthened, the ΔG° value shifted more negatively in comparison to water. The spontaneous nature of CTAB binding with MO was suggested by the negative value of ΔG°. As the concentration of CTAB in the water & alcoholic media increased, the MO absorption dramatically blue-shifted from 464 nm (water) to 440–450 nm (propanol, butanol). These findings showed that the alkyl chain plays a role in reducing absorbance. The MO absorbance in the water, 1-propanol or 1-butanol media decreased with increasing CTAB concentration (hyperchromic shift).

Keywords

• CTAB
• Propanol
• Butanol