Candidate of the doctorate: Alexander Goryan
Supervisor: Oleg Antzutkin
Contact person LKAB: Seija Forsmo
Research area: Partikel technology in LKAB:s processes
Principal Investigator: Prof. Oleg N. Antzutkin (Division of Chemistry)
PhD student: Mr. Alexander S. Goryan (Division of Chemistry)
"Milos" bentonite is used as the principal binder in iron-oxide pellets, the principal product of LKAB. It is calcium-montmorillonite type of bentonite, in which calcium is exchanged by sodium to gain better rheological, swelling and binding properties of bentonite. Because of a high concentration of Ca2+ and Na+ ions in the process water of LKAB's pelletizing plant in Kiruna, sodium cations in "Milos" bentonite may be exchanged back to calcium ions during the balling process of iron-oxide pellets and the binding properties of "Milos" bentonite may be, therefore, compromised. This may lead to a decreased strength of the "green" pellets and to a large fraction of broken pellets returning back to balling drums that decreases the efficiency of the whole balling process.
Our goal in this project is to investigate how fast and to what extend Na+ ions will be exchanged by Ca2+ when bentonite was swelling solutions of these ions at concentrations close to those found in the process waters of LKAB. Solid-state 23Na NMR spectroscopy was chosen for quantification of Na+-/Ca2+ ion-exchange and for measuring of its timescale. In parallel, 1H-diffusion NMR measurements on water-saturated Ca/Na-exchanged "Milos" bentonite samples will be performed. The following properties will be correlated: (i) a change of the content of sodium in bentonite, (ii) a change in the coefficient of self-diffusion of water in bentonite and (iii) a change of binding, swelling and other rheological properties of bentonite. 13C, 29Si and 23Na solid-state NMR experiments will be performed on bentonite/organic binder mixtures. Understanding of interactions between these two binders (inorganic/organic) and their synergy in the balling process of iron-oxide pellets is an important current issue for LKAB's iron-oxide pellets with a desired low content of Si.