Behavior of Iron Under Pressure Acid Leaching of Nickel Laterite Ores

This paper outlines the use of an innovative system for thein situinvestigation of hydrothermal reactions by X-ray diffraction. The key features are the use of: (i) a purpose-built capillary reaction vessel which allows close emulation of the conditions present in mineral processing plants; (ii) MoKα radiation, to ensure that the X-ray beam penetrates through the capillary, and (iii) an Inel CPS120 position-sensitive detector, to enable simultaneous collection of a wide range (120° 2θ) of diffraction data. The pressure acid leaching (PAL) of nickel laterite ores is used to illustrate the capabilities of this system, with a particular focus on the PAL of saprolite in strong H2SO4at 493 K. Saprolitic ore, which largely consists of serpentine mineral phases [(Mg,Fe,Ni,Al)3(Si,Al)2O5(OH)4], undergoes a number of mineralogical changes during both the acid leaching reaction and subsequent cooling, thus making it difficult to examine accurately using traditional post-reactionex situtechniques. In particular, kieserite (MgSO4.H2O), which forms during leaching, has a negative temperature coefficient of solubility, causing it to dissolve on cooling. Thein situtechnique described in this paper allows the direct observation of kieserite formation during the saprolite PAL at 493 K and its dissolution upon cooling to ambient temperature.

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Time-resolved diffraction studies into the pressure acid leaching of nickel laterite ores: a comparison of laboratory and synchrotron X-ray experiments

Journal of Applied Crystallography ◽

10.1107/s0021889808006894 ◽

2008 ◽

Vol 41 (3) ◽

pp. 572-583 ◽

Cited By ~ 16

Author(s):

Nicola V. Y. Scarlett ◽

Ian C. Madsen ◽

Barry I. Whittington

Keyword(s):

Method Development ◽

Acid Leaching ◽

Ex Situ ◽

Nickel Laterite ◽

Time Resolved ◽

X Ray ◽

Laterite Ores ◽

A Minor ◽

Pressure Acid Leaching ◽

Kinetics Of

This paper compares time-resolved diffraction experiments that have been performed using laboratory and synchrotron X-ray sources. The experiments investigated the mechanism and kinetics of pressure acid leaching of nickel laterite ores. The sample environment was a purpose-built capillary reaction vessel, and extensive method development was conducted in the laboratory using Mo Kα radiation prior to repeating and extending the experiments at the Daresbury Synchrotron Radiation Source, beamline MPW6.2. In general, the synchrotron results confirmed the findings from previously reported laboratory work and also confirmed the presence of a minor phase that had been ambiguous in the laboratory experiments,i.e.the formation of hematite in the pressure acid leaching of saprolite. The synchrotron measurements also extended the experimental programme to include poorly diffracting laterite components that could not be examined in the laboratory,e.g.nontronite. The results from these components supported the reaction mechanisms determined fromex-situanalyses conducted in larger scale autoclaves.

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