Detailed Adsorption Studies of Active Humic Acid Fraction of a New Binder on Iron Ore Particles

Humic acid (HA) is used as one of organic active fractions of a new binder in the process of iron ore agglomeration. The purpose of this study was to determine the detailed adsorption characteristics of HA onto iron ore particles. The results demonstrated that the adsorption of HA was strongly dependent on solution pH, concentration, contact time and temperature. The chemical adsorption controlled the adsorption process of HA onto iron ore particles as typically found in earlier reported results. The adsorption kinetics of HA onto iron ore particles at different testing conditions was well described by the first-order model, which indicated that the adsorption rate is proportional to the concentration of HA. The adsorption isotherms of HA were determined by the fittings of the experimental data to two well-known isotherm models involving models: Langmuir and Freundlich. The Freundlich model (R-square>0.97) appeared to fit the adsorption better than the Langmuir adsorption model, which indicated that multilayer absorption dominates the reaction of HA with iron ore particles. The value of exponent n (n>1.0) for the Freundlich model indicated that the multilayer absorption of HA was hampered because of the appearance of the adsorbed HA on iron ore particles. These findings are useful for evaluating the adsorption capacity of MHA binder.