Study on the interaction of natural dye cochineal with FeSO4 (II)

The interaction of natural dye cochineal with FeSO4 as a mordant was studied in the solution. In this study, the effects of interaction conditions including pH value and concentration of mordant were investigated. Cochineal produced a range of scarlet, pink and red hues. The results showed that the presence of the mordant and value of pH solution are the significant factors on the absorption and wavelength of dye. The λmax of cochineal dye at pH 4 and 6 were obtained 492 nm and 526 nm, respectively. Moreover, λmax of cochineal in the interaction with FeSO4 shifts to higher wavelengths. The results indicated that the interaction of cochineal by mordant in pH 6 is more than pH 4. The presence of both carbonyl and hydroxyl groups in anthraquinone structure of cochineal is probably responsible for its behavior interaction with mordant.