The separation of arsenic from copper in a Northparkes copper–gold ore using controlled-potential flotation

Abstract

In order for the high-arsenic regions of the Northparkes copper–gold orebody to be beneficiated economically, tennantite ((Cu,Fe) 12As 4S 13) present in the ore needs to be rejected to enable copper concentrates to meet the typical smelter penalty level of 2000 ppm As. Using a composite sample of high-arsenic drill cores from Northparkes it was possible to selectively separate tennantite from chalcopyrite (CuFeS 2) and bornite (Cu 5FeS 4) using controlled-potential flotation. The separation was made on a bulk copper–arsenic concentrate after reducing the pulp potential to about − 150 mV SHE at pH 12 and floating the tennantite from the other copper minerals. The basis of the separation relies on findings that the lower limiting pulp potential threshold for tennantite is lower than that for chalcopyrite such that there is a potential window in the reducing region where tennantite is strongly floatable but chalcopyrite is not. Little or no selectivity between tennantite and chalcopyrite was found in the oxidising pulp potential region for the range examined. From the composite sample tested, which had a head grade of 0.11% As and 1.2% Cu, it was possible to produce a low-arsenic high-copper concentrate containing 52% of the non-tennantite copper and assaying 2600 ppm As. Computer simulations have shown that for a feed containing a more typical arsenic and copper level (200 ppm As and 1% Cu) the efficiency of separation should be sufficient to concentrate about 61% of the copper in a product assaying less than 2000 ppm As. A conceptual flowsheet for arsenic rejection from Northparkes copper–gold ore, based on the findings from this study, is presented and discussed in this paper.