Adsorption of Tiron onto Alumina

It has been shown recently that small organic molecules, used as dispersants in the colloidal processing of ceramic powders to adjust the forces between the particles, are quite efficient in preparing aqueous suspensions of high solid loadings and low viscosity. One of them is 4,5-dihydroxy-1,3-benzenedisulfonic acid, disodium salt monohydrate, ((OH)2C6H2(SO3Na)2·H2O), commercially known as Tiron. The adsorption of Tiron, as a function of its concentration and solution pH, onto alumina was investigated by the solution depletion method, applying UV spectrophotometry. KNO3 (10-2 mol/l) was used as the background electrolyte. The obtained results indicate an increase in the amount of adsorbed Tiron with its increasing concentration. The maximum adsorption was recorded at pH≈7 when the Tiron molecule was uncharged, i.e. undissociated (pKa1=7.6). The experimental data were fitted with different adsorption isotherm models. The maximum amount of Tiron adsorbed, as well as the constants of adsorption process were calculated.