Geology Reference
In-Depth Information
Production also involves strong chemical treatments either with alkali, sulphuric
acid and/or hydrochloric acid, plus conventional roasting processes. Explicitly for
the case of REE, a chemical separation of the different elements either by solvent
extraction or ion-exchange processes must be added. It also requires reduction
and electro-refining in extremely harsh conditions due to the high reactivity and
easily contaminated tendency of REE. Furthermore, the process of obtaining rare
earths is as energy intensive as that of titanium or alkali-earth elements preparation
with the alloying processes at high temperature and inert atmosphere contributing
further to energy consumption and the subsequent environmental impact. Their
cumulative impacts are di
cult to ascertain due to the overwhelming diversity of
chemical routes and the type of product that can be obtained (a mix or pure REO,
mischmetal, pure element at different purity grades, or alloys for magnets and other
applications). As many REO are exported, transport costs to the refiner's site are
also a key consideration. Furthermore, there is a worrying lack of transparency in
field data for REO production (which come mainly from a single country producer)
and for REO processing (which is carried out in many different countries). Whilst
there are some partial LCAs on REE preparation, a comprehensive LCA map is
still missing.
Specifically, the REE industry in China emits more than 13 billion cubic meters
of waste gas per year in the smelting and separation processes alone. For every tonne
of REO the following detrimental effects are produced (Gibson and Parkinson, 2011;
Chen, 2010):
9,600-12,000 cubic meters of waste gas with 8.5 kg of fluorine, hydrofluoric acid,
sulphur dioxide and sulphuric acid.
75 m
3
of acidic wastewater.
1 tonne of radioactive waste residue diluted in water.
2,000 tonnes of mine tailings containing Th (20.4 m
3
of waste rock/t of REO).
Other problems for South Chinese mines relate mostly to illegal mining which
can easily result in uncontrolled toxic wastes entering the public water supply, loss of
vegetation, soil pollution and erosion and contamination of groundwater and rivers
generally.
Koltun and Tharumarajah (2008, 2010) undertook a LCA study using Sima Pro
7.1 of the REE used for magnesium alloys whereby the RE mineral contains 75%
bastnaesite and 25% monazite with separate REO preparation routes. Table 8.1
shows the results of Koltun and Tharumarajah (2008) in the mining, beneficiation
and separation of REE ore at Bayan Obo per kg of total REO (TREO).
Their investigation considers the production of the REO at Bayan Obo, Inner
Mongolia and the reduction and separation process at the purchaser's site (Aus-
tralia). They allocated energy and environmental costs in proportion to the price
of each commodity whereby Bayan Obo produces iron and niobium ore as its main
bulk product. At this site, for each kg of total REO, 170 kgs of iron ore are pro-
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