Download Process mineralogy of non-sulphide zinc ore from Mehdiabad

Process mineralogy of non-sulphide zinc ore from Mehdiabad deposit and
feasibility study of extraction of hematite-goethite as by product by
magnetic separation method
Abstract
Non-sulphide zinc deposits are important potential resources of zinc and other metals, The Mehdiabad
deposit in South eastward of Yazd is an example of them, in which characterization of the
mineralogy, texture and grade for processing has been carried out.
The ore concentrations, mainly consisting of oxidized Zn minerals (smithsonite and hemimorphite and
chalcophanite) and Fe minerals(hematite and goethite), Gangue minerals consist of cerusite, dolomite,
barite, calcite and quartz.
The objectives of this study were to examine the possibility of iron extraction as byproduct, of oxide
ore by magnetic separation method. Another goal is evaluating the possibility of pre concentration of
low grade zinc ore by mineralogical studies on production of magnetic separation.
Magnetic separation and cleaner tests resulted in an up gradation of iron content from feed value of
24.6% iron to maximum 33.4% iron with recovery of 55%.
Mineralogical studies which were carried out on zinc ore samples and production of magnetic
separation experiment, indicated that approximately %30 of zinc minerals are intimately intergrown
with the hematite and goethite minerals and therefore difficult to separate with leaching process.
Therefore magnetic separation can be used for pre concentration of Mehdiabad zinc ore.
Introduction
As well as many other metal projects, also nonsulfide zinc ores have been recently put on hold, due to
the current difficult economic situation. However, research on mineralogy and metallurgy is still
active for most of them, ready to be applied to each individual deposit, should the economic
conditions improve in a not too far future.
Nonsulfide ores have been subdivided in Hypogene and Supergene deposits (Large, 2001; Hitzman et
al., 2003; Boni, 2005). The Supergene Nonsulfide Zn(Pb) deposits, which are so “Zinc nonsulfides” is
a very general term, which comprises a whole series of minerals (Large, 2001; Hitzman et al., 2003;
Boni, 2005a).
The typical mineral associations of a supergene Zn(Pb) deposit can be either very simple or extremely
complex, depending on the mineralogy of the primary ores. Most deposits of this type consist of
mixed blends of mineral phases: carbonates (mainly smithsonite [ZnCO3], hydrozincite
[Zn5(CO3)2(OH)6] and cerussite [PbCO3]); silicates (hemimorphite [Zn4Si2O7(OH)2_H2O] and
willemite [Zn2SiO4] and sauconite [(Na0.3Zn3(Si,Al)4O10(OH)2_4(H2O)]), commonly associated
with several Mn/Fe (hydr)oxides (goethite, hematite, coronadite) generally containing variable
amounts of base metals. Zinc can also be hosted in Barite and phyllosilicates such as chlorite-like
clays (Blot et al., 1995) and in Muscovite /illite (Mondillo et al., 2014).
mixed blends of mineral phases of supergen deposits, derive from the weathering of pre-existing Zn
sulfide mineralization, which might also contain Pb (commonly Mississippi Valley Type [MVT],
SEDEX, and Carbonate Replacement deposits). The metals (Fe, Zn, Pb), leached out from the
sulfides, are transported in solution by meteoric waters through pore spaces and fractures of the host
rock (Hitzman et al., 2003). Rocks with buffering capacity (commonly limestone, dolomite or
sandstone) may trigger the precipitation of secondary minerals from the metal-rich solutions.
Although the oxidization of primary Zn sulfides is a relatively common process, economic non sulfide
deposits are less common, owing to the unique condition necessary to form and preserve these
supergene concentrations.
The economic value of nonsulfide zinc ores is strictly dependent not only on the geological
knowledge of each deposit, but mainly on the specific characteristics of the mineralogical association
and on the interaction of zinc/ lead-and gangue minerals during processing (chemical and physical) of
the ore.
In any extraction scenario, the response of the ore feed to different processing methods is a direct
function of the mineralogical components and particle size distributions in the ore material. In order to
fully understand the operating requirements for processing, such as the acid consumption, the likely
recovery, the presence of detrimental substances, or the energy consumption, it is important to
develop an understanding of the mineralogical variability of the ore feed.
The Mehdiabad deposit, subject of this paper, is an example of the above-mentioned supergene
nonsulfide ores. The current study, has been done according to previously studies on mineralogy and
leaching experiment results of low grade zinc ore. (bayazid hosseini 2011; seywan mohammdi.,
2013), leaching results had shown that in optimim condition, the zinc recovery is less than 70%, thus
for specifying the type of insoluble zinc, the completed mineralogy studies has been carried out on
feed ore and magnet sepration samples.
Furthermore, The exponential demand, improved socio-economic conditions, stringent environmental
regulations on mining industry and depletion of massive compact high grade anhydrous iron oxide
ores necessitated the processing and utilization of low grade iron ore lumps and fines and mine waste
dumps. Considering the low grade iron (aasaying 24% Fe) of Mehdiabad deposite, evaluation the
feasibility of extraction of, hematite-ore as byproduct by magnet sepration method has been
conducted.
The objectives of this study were to examine the possibility of iron extraction as byproduct, of oxide
ore by magnetic separation method. Another goal is evaluating the possibility of pre concentration of
low grade zinc ore by mineralogical studies on production of magnetic separation.