Reductive acid leaching of laterite and metal oxides — A review with new data for Fe(Ni,Co)OOH and a limonitic ore

Abstract

The reductive leaching of nickel laterite has attracted the interest of many researchers due to the enhanced kinetics of nickel and cobalt dissolution in the presence of acids and reducing agents during atmospheric, pressure, heap or bio leaching processes. Systematic studies on synthetic oxides and natural ores can shed light on the reaction mechanism and lead to investigations of beneficial reagents for further studies. This paper briefly reviews the literature and describes a comparative study of metal leaching from synthetic goethite spiked with nickel or cobalt and a limonitic laterite ore to rationalise the role of reducing agents in acid media. Results are discussed on the basis of the effect of speciation, surface chemical reactivity of oxides and heterogeneous kinetic models.Key words: Laterite, synthetic oxides, reductive leaching, kinetics, adsorption. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

Reductive atmospheric acid leaching of lateritic smectite/nontronite ores in H2SO4/Cu(II)/SO2 solutions

“…The values of LE (Co) and LE (Mn) were approximately 60% or more with SO 2 alone (Test (ii) in Table 5 (Das et al, 1997;Senanayake et al, 2011). The maximum values of LE (Co) and LE (Mn) from the smectite ore D vary in the range 95-97%, in comparison to almost 100% in the case of limonites (Senanayake and Das, 2004;Senanayake et al, 2011). Table 5 shows that the value of LE (Fe) in the weak acid SO 2 in Test (ii) is nearly doubled (from 10.3% to 22.4%) caused by Cu(II)/SO 2 in Test (iii).…”

“…goethite at atmospheric pressure (Surana and Warren, 1969;Warren and Hay, 1974;Byerley et al, 1979;Kumar et al, 1993;Petrie, 1995;Senanayake et al, 2011). The leaching of Mn from manganese ores, nodules, wads, etc.…”

“…Thus, reductive leaching under atmospheric conditions in the presence of SO 2 has been adapted to achieve more than 90% nickel and cobalt extraction from limonitic and saprolitic ores (Das et al, 1997;Kittelty, 2008;Lee et al, 2005;Senanayake and Das, 2004;Senanayake et al, 2011). The reductive leaching may prove to be a potential process option for future treatment of various lateritic ore bodies.…”

“…The presence of copper(II) has a beneficial catalytic effect during SO 2 leaching of magnetite and laterite ores. Copper(I) ions produced by the reaction between sulphur dioxide and copper(II) act as a reducing agent (Byerley et al,1979;Das et al, 1997;Senanayake et al, 2011). However, as copper(II) produced by the oxidation of copper(I) by high-valent metal oxides or oxy-hydroxides is reduced back to copper(I)…”

“…based limonitic ore from different origins using SO 2 as a reductant (Das et al, 1997;Kanungo et al, 1988;Senanayake and Das, 2004;Kittelty, 2008;Senanayake et al, 2011). A recent study has extended the AAL leaching system to nontronite type laterite ore from Western Turkey (Buyukakinci and Topkaya, 2009) and copper catalysed RAAL system to a smectite ore from Western Australia Das et al, 2010).…”