Abstract
Lithium’s (Li) value has grown exponentially since the development of Li-ion batteries. It is usually accessed in one of two ways: hard rock mineral mining or extraction from mineral-rich brines. Both methods are expensive and require a rich source of Li. This paper examines the potential of agro-mining as an environmentally friendly, economically viable process for extracting Li from low grade ore. Agro-mining exploits an ability found in few plant species, to accumulate substantial amounts of metals in the above ground parts of the plant. Phyto-mined metals are then retrieved from the incinerated plants. Although the actual amount of metal collected from a crop may be low, the process has been shown to be profitable. We have investigated the suitability of several plant species including: Brassica napus and Helianthus annuus, as Li-accumulators under controlled conditions. Large plant trials were carried out with/without chelating agents to encourage Li accumulation. The question we sought to answer was, can any of the plant species investigated accumulate Li at levels high enough to justify using them to agro-mine Li. Results show maximum accumulated levels of >4000 mg/kg Li in some species. Our data suggests that agro-mining of Li is a potentially viable process.
Highlights
Agro-mining describes a process that uses plants to abstract metals from soils [1]
The authors of this study found that the ethylenediaminetetraacetic acid (EDTA) molecule remained intact for up to days, whereas EDDS was biodegraded rapidly in the activated sludge
Brassica napus despite not been a natural Li accumulator performed significantly better when it came to Li accumulation when both chelating agents were applied, EDTA treated plants showing a marginally higher level that
Summary
Agro-mining describes a process that uses plants to abstract metals from soils [1]. The process ideally harvests metals from high biomass crops which are grown in metal rich soils, those associated with sub-economic mineralization [2]. The crop is harvested, and incineration of the biomass generates a high-grade bio-ore. Agro-mining offers the possibility of exploiting metal rich soil substrates that are otherwise uneconomic to mine, its impact on the environment is minimal compared to conventional mining methods (opencast, underground) [4]. Agro-mining can be thought of as an extension of the same process as growing fuel (alcohol) from crops [5]. The agro-mine metal is virtually sulphur free unlike metals extracted from ore bodies, so the smelting process requires less energy and does not contribute significantly to acid rain [7]. The metal concentration of a bio-ore is often higher than conventional ores, requires less storage space
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