Developing and understanding the bentonite fiber bonding mechanism

The classically accepted mechanism for binding fine iron ore concentrates b y bentonite clay is that the clay becomes hydrated, expands, disperses, and then dries into a bonding film that holds the iron ore particles together However, bentonite has been observed to form a fibrous structure on the sur face of foundry sands, which is relevant because foundry sands are produced under similar conditions to iron ore pellets. The classical bentonite bind ing mechanism cannot explain how bentonite fibers are formed. Is a more com plete understanding of bentonite binding mechanisms important? How can the iron ore pellet industry benefit? In this paper, scanning electron microsco py was used To attempt to image bentonite fibers formed on the iron ore con centrate that composes the pellets. It was determined that bentonite fibers were not inherently formed during iron ore pellet production. Experimental methods were designed that allowed bentonite fibers to be developed and st udied. The bentonite fiber mechanism has been developed into a new theory. Based an this theory, experiments conducted under conditions that would pro mote formation of bentonite fibers were found to be associated with an incr ease in bonding. Once the fundamentals of bentonite binding mechanisms are completely understood, what can be changed to improve the quality of iron o re pellets' Implications to improving iron ore pellets are discussed. How c an this knowledge be used to benefit other industries that use bentonite as a binder? (C) 2001 Published by Elsevier Science Ltd. All rights reserved.