Effects of metal cations on the fulvic acid (FA) adsorption onto natural iron oxide in iron ore pelletizing process

Organic binder is a significant substitution of the bentonite in iron ore pelletizing process, reducing the exploitation of clay resource and improving the quality of pellets. Fulvic acid is one of the important functional groups of modified humic acid (MHA) binder which is invented by the authors and can be used as an excellent composite binder in pelletizing. This work aims to further study the effect of metal cations on FA adsorption onto natural pure oxides and the wet strength of green pellets made with MHA binder via batch adsorption and pelletizing experiment. The adsorption density of FA onto the natural oxides was significantly improved after adding the metal cations. The zeta potential values of the magnetite particles coated by FA became less negative after adding metal cations before the pH value of 9.2 but more negative after 9.2. The XPS analysis and SEM imaging indicated that the metal cations served as a bridge between FA molecules and the surface of magnetite particles, so that the adsorption of FA onto magnetite was promoted. In addition, the viscosity of FA increased after adding the metal cations. Both of these changes were found to be beneficial for the wet strength of MHA binder pellets. (C) 2016 Elsevier B.V. All rights reserved.