Adsorption equilibria of anionic dyes Eosin Yellow and Reactive Blue 4 on amino-containing ormosils
Adsorption of anionic dyes Eosin Yellow and Reactive Blue 4 by amine containing ormosils has been studied. The probing of the material surfaces with the H+ ions has been used to characterize quantitatively protolytic equilibria of immobilized amines. The Langmuir adsorption model is too simplified and does not provide the correct description of the dye adsorption. The adequate description of adsorption equilibria as well as the reasonable presentation of chemistry involved in the adsorption processes was achieved within the framework of the model ofpolydentate binding. This model takes into account both the real ion exchange mechanism of the dye binding and the positive cooperativity effects influencing the adsorption equilibria. The effective sorption capacities of the studied materials in respect to the studied dyes reach 100 Jlmol·g -1. The high values of the constants of adsorption equilibria evidence that amine containing ormosils are efficient adsorbents for removing anionic dyes. The weakly acidic medium provides high degrees of the dye adsorption, while the regeneration of the adsorbents should be performed with the use of weakly alkaline solutions. The amine containing ormosils remain full sorption capacities after at least five adsorption-desorption cycles.