Interfacial reaction between humic acid and Ca-Montmorillonite: Application in the preparation of a novel pellet binder

In this study, a comparative study of adsorption characteristics of humic acid (HA) onto Ca-montmorillonite and Na-montmorillonite were carried out to guide the preparation of a novel composite binder for iron ore pellets, namely humic acid modified bentonite (HAMB). Using Ca-montmorillonite (Ca-Mt) as a representative, the adsorption mechanisms of HA onto montmorillonite were studied by XRD, zeta potential, FTIR and XPS analyses. The results indicated that HA was adsorbed onto Ca-Mt mainly via complexation and H-bonds. The DFT calculation and molecular dynamics simulation were also carried out to further determine the adsorption mechanisms of HA onto Ca-Mt. Molecular dynamics simulation analyses showed that the complexation reaction between carboxyl, hydroxyl groups of HA and Ca ions in Ca-Mt is dominant in HA adsorption. And the pelletizing experiments indicated that the HAMB binder prepared at a pH value of 7 had excellent application effect in iron ore pelletization.