Dearsenization of ore by high gradient magnetic separator

Tatsuya OKI National Institute of Advanced Industrial Science and Technology (AIST), JAPAN

Principal Research manager Representative Chairman in copper ore

In the near future, the grade of copper ore in the world will decline and there will be concern that the concentration of arsenic coexisting will increase.

Advanced Copper ore with low As physical separation (Sorting) Dearsenization Copper ore (concentrate) 2 High gradient magnetic separator

Generates extremely large magnetic force (B･ΔB) locally with normal conducting magnets, and fine particles can also be recovered magnetically

Non mag

Mag

Matrix Magnet (Magnetic filter) Magnet

slurry

Magnetic flux density distribution (T) 3 High gradient magnetic separator AIST have already put into practical use of HGMS system to recover only LAP containing Tb from mixed waste phosphor of 5 μm size.

Size is small and separation range is extremely narrow.

・LAP recovery:70％ ・98.9% luminous flux of virgin powder realized

In this study, we examined the possibility of dearsenization of copper ore by applying this technology. 4 Characterization of copper ores There is no copper-free arsenic ore in the concentrate samples. We have to separate “the copper ore containing no arsenic” from “the copper ore containing arsenic”.

Index Minerals Cu As Fe

Enargite ● ● × ● 〇 ● ● 〇 Chalcopyrite ● ● 〇 ●

Sphalerite

Quartz

Tennantite ● ● ● Arsenopyrite ● ● Realgar ● 〇：Recovery ×：Removal

5 Characterization of copper ores

Precise magnetic susceptibility analysis for pure mineral samples by SQUID magnetometer

As free copper ore Antiferromagnetism Paramagnetism

Enargite Arsenopyrite Tennantite Chalcopyrite

Pyrite・Marcasite 10-5 10-6 10-6 10-5 10-4 10-3

Magnetic susceptibility( - ) ≒

Since the separation point is smaller by one digit than the phosphor, it is difficult to recover 5 μm particles, but the relationship is similar.

6 Separation tests Representative separation results for the sample A Most of Enargite can be removed. Magnetic Magnetic Feed(20～53μm) Cleaning Roughing

Non magnetic Magnetic Enargite 200μm Scavenging

Index Minerals Cu As Fe

Enargite ● ● × Chalcocite ● 〇 Excessive scavenging leads to the Bornite ● ● 〇 recovery of fine Enargite particles. Chalcopyrite ● ● 〇 Pyrite ●

Sphalerite

Quartz 7 Separation tests Representative separation results by a multistage magnetic separation system Cu As Good results Sample A Recovery Content Content Removal Minerals Cu As Fe % % % % Enargite ● ● ● Feed － 31.2 1.76 － Chalcocite ● 〇 Final product 1 41.1 49.5 0.27 96.0 Bornite ● ● 〇 Final product 2 51.4 46.0 0.41 91.9 Chalcopyrite ● ● 〇 Final product 3 57.9 43.5 0.54 87.2

Cu As Bad results Sample B Recovery Content Content Removal Minerals Cu As Fe % % % % Enargite ● ● ▲ Feed － 39.5 5.63 － Chalcocite ● △ Final product 1 50.6 43.2 4.24 65.2 Bornite ● ● × Final product 2 74.7 41.5 4.27 46.3 Chalcopyrite ● ● × Final product 3 85.9 39.5 4.59 29.9

The effect of magnetic selection depends on the mineral species. 8 Conclusions

In this study, the possibility of dearsenization of copper ore using a high gradient magnetic separator was investigated.

(1) There is no copper-free arsenic ore in the concentrate samples. It is necessary to separate “the copper ore containing no arsenic” from “the copper ore containing arsenic”.

(2) Since the separation point of copper ore is smaller by one digit than waste phosphor, it is difficult to recover 5 μm particles, but the relationship is similar.

(3) As a result of testing two samples, one sample was a good result and the other was a bad. It was presumed that the effect of magnetic selection depends on mineral species.

9