Study of the mechanism for improving green pellet performance with compound binders

In this study, the characters of bentonite organic binders were investigated by analytical methods, including X-ray diffraction, zeta potential, and scanning electron microscope. The results showed that the surfaces and the edges of montmorillonite layers reacted with carboxyl groups or oxhydryl groups of expanded starch or carboxymethyl cellulose (CMC), enhancing the surface electronegativity of the bentonite. The addition of organic binders reduced the contact angle between the bentonite and magnetite and enhanced the hydrophilicity of bentonite surfaces. Based on the polymer chains of organic binders, the house-of-cards structure formed by a compound binder was more stable than when formed by bentonite alone. The non-stripped layers in bentonite were peeled off under the action of chemical bonds. At the same time, improved bentonite dispersion in pellets was observed, with decreased bentonite particle size and increased surface area. The solid bridges produced by the reaction between magnetite and Mg2+ in the montmorillonite layer restrained pellet expansion, which thus improved the decrepitation temperature during the heating process.