Abstract
In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO2 partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation reaction include quasi-amorphous colloidal silica, chromium-rich metallic particles, and ferro-magnesite ((Mg1−x,Fex)CO3). Carbonated olivine was subsequently leached using an array of inorganic and organic acids to test their leaching efficiency. Compared to leaching from untreated olivine, the percentage of nickel extracted from carbonated olivine by acid leaching was significantly increased. It is anticipated that the mineral carbonation pre-treatment approach may also be applicable to other ultrabasic and lateritic ores.
Highlights
In the last few decades, traditional nickel resources have become scarcer because of ramping global production and growing demand [1]
This paper reports the results of a series of tests that aimed to: (i) find the optimal carbonation conditions that maximize the desired mineral and morphological alterations; (ii) characterize the carbonated products with a focus on the fate of nickel; (iii) compare the leaching performance of an array of organic and inorganic acids, and assess the efficiency and extent of nickel extraction from carbonated olivine compared to natural olivine; and (iv) provide the proof-of-concept of using carbonation as a pre-treatment step for nickel recovery from low-grade silicate ores and elucidate directions for future research
The objective of this work was to look at the extraction of nickel from a low-grade silicate ore, namely olivine
Summary
In the last few decades, traditional nickel resources have become scarcer because of ramping global production and growing demand [1]. Nickel is more abundantly present in the Earth’s crust than copper and lead, but the availability of high-grade ores is rather limited [2]. Magnesium-iron silicates, minerals that are widely distributed on the Earth’s crust and that contain relatively dilute, yet considerable amounts, of nickel arise as one possible, yet challenging, opportunity. The main objective of this study was to investigate the possibility of processing olivine ((Mg,Fe)2SiO4) for the production of nickel. Olivine is solid-solution of iron- and magnesium-silicates containing relatively small amounts of nickel and chromium, and is the precursor of weathered lateritic ores. The use of olivine as a nickel source could, possibly solve the scarcity problem of high-grade ores. In this work a novel approach was investigated, whereby the mineral is first carbonated in a pre-treatment step before the nickel is extracted by leaching. CO2 is utilized primarily as a processing agent; such an approach can be termed “carbon utilization” ( turning CO2 from a waste into an acid)
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