Abstract
High temperature pressure oxidation of a low-grade nickel concentrate was examined to demonstrate the potential benefits and shortcomings of this approach. The high iron sulfide content ensured that acid generation was much greater than for higher grade concentrates. This results in the formation of basic iron sulfate phases and a significant amount of sulfuric acid. Kinetic sampling during pressure oxidation tests also demonstrated the transformation of sulfide minerals, including the oxidative transformations of pentlandite to violarite and then to vaesite, the latter phase not previously noted in studies of this kind. Finally, addition of a divalent metal sulfate buffer, here magnesium sulfate, mitigates the formation of basic iron sulfates but with greater generation of sulfuric acid in the leach liquor. Under the conditions employed in this study, this acid could be employed to leach other nickel-containing materials such as nickel laterites.
Highlights
The hydrometallurgical processing of nickel sulfide concentrates per se is not commonly practiced commercially though several processes for these feeds have been developed and tested at pilot scale [1,2]
Changes in composition the composition of iron hydrolysis products in leach the leach residue for samples taken during the pressure oxidation of nickel concentrate in molal magnesium taken during the pressure oxidation of 9.2% w/w “aged” nickel concentrate in 1 molal magnesium
The current study examined the leaching behavior of a low-grade, high iron content nickel concentrate allowing the following conclusions to be made:
Summary
The hydrometallurgical processing of nickel sulfide concentrates per se is not commonly practiced commercially though several processes for these feeds have been developed and tested at pilot scale [1,2]. A low-iron matte with iron content in the range 0.5–4% is targeted and this has meant that there has been a trend to eliminate as much of the iron sulfides as possible, through milling, during concentrate production [5]. The conversion of sulfide to elemental sulfur or sulfate rather than sulfur dioxide; The ability to process feeds with significant impurities such as arsenic due to fixation as a stable ferric arsenate product; The ability to treat low nickel-, high magnesium-containing feeds and; Higher recoveries of cobalt. A high iron, low nickel concentrate was treated by pressure oxidation at 250 ◦ C, albeit a somewhat higher temperature than typically employed [7], to demonstrate some of the benefits and shortcomings of this approach. Alternative methods to mitigate some of the shortcomings are proposed
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