Adsorption of Methyl Orange on Starches

Adsorption characteristics of methyl orange were investigated on kudzu, sweet potato, corn, rice, wheat, potato and snake gourd starches. No adsorption of methyl orange, an anionic dye, was observed on potato starch and snake gourd starch because of the presence of phosphate esters. Adsorption isotherms were found to fit both the Langmuir equation and Freundlich equation in all others. The degree of adsorption by kudzu, sweet potato, corn and wheat starches was related to the number of hydroxyl groups. We suggested methyl orange was confined to a monolayer on surface hydroxyl groups of the starches.