Iron romoval from Iwate koshitsu clay (hard claystone) by high gradient magnetic separation (HGMS) method was investigated. Effects of operation conditions such as particle size, kind of matrix, pulp density, feeding rate, magnetic field strength on the iron removal were experimentally studied.
It is important for HGMS method to select an adequate matrix against the clay particle size. For instance, matrix FW was suitable for koshitsu clay having 5000 particle size of 4.3μm and 8000 size of 17μm, but not matrix CX. On the contrary, matrix CX was fit for the clay having 5000 size of 52μm and 80% size of 205 μm, but not matrix FW.
Between pulp densities of 5-30 wt.%, iron removal from the koshitsu clay showed almost same results. However the feeding rate had a great influence on the clay recovery results. Nonmag yield increased from 67.6% at 22.1 m/hr of linear velosity to 88.700 at 179 m/hr while the nonmag iron content remained almost constant values of around 1.10 wt.% under the following experimental conditions ; sample : koshitsu clay H4-1, feed iron content : 3.86%, feed 5000 particle size : 0.4μm, pulp density : 5 wt.%, matrix : FW and magnetic field strength : 9.7KG. Between the linear volocity of 179 and 492 m/hr, nonmag yield and iron content showed nearly constant values of 9000 and 1.20 wt.%, respectively.
Also the magnetic field strength effected considerably on the iron removal results. Hinger than 3.0 KG, almost all siderite, in the clay could be separated and the iron content decreased less than 1.88 wt.% from around 9.80wt.%, however lower than 3.0 KG, iron content extremely increased as decreasing magnetic field strength under the following conditions ; sample : H4-2, feed 50% size : 52μm, matrix : CX and linear velocity : 179 m/hr.
On the whole, good results for the iron removal from koshitsu clay by HGMS method were obtained at the higher linear velosity and rather low magnetic field strength.

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