3．Microbial recovery of SIMs by biosorption

Previously, we found that the metal ion-reducing microorganism, Shewanella algae, exhibits fast growth with an inexpensive nutrient source, confirming that the low cost and rapid production of bacterial biomass adsorbents can be applied as an inexpensive bio-material for recovering indium from solution (Ogi et al., 2012). Using this bio-adsorbent, a system for the novel recovery of indium from the leachate of used LCD panels was proposed and its effectiveness demonstrated (Figure 4, Higashi et al., 2011). The features of this bio-recovery method are as follows.

  • Significant reductions in energy and material consumption with a small environmental load compared to conventional technology;
  • Indium from dilute solution can be selectively separated and concentrated rapidly inside the cell within 10 minutes;
  • After combusting indium-containing cells, concentrates of 40% indium content can be easily recovered.
Recently, we have found that this biosorption method is also effective in the recovery of neodymium and gallium.

 

Taking advantage of the ability of the microorganisms to separate and concentrate neodymium from the solution inside the cells, a soft path employing environmental -friendly and low-energy processes is constructed to recover neodymium using leachates of used permanent magnets as the target. A new bio-recovery system will be developed by establishing the operating conditions that can fully utilize this microbial ability to recover neodymium efficiently and economically for the purposes of continuous treatment of neodymium-containing solutions.

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Figure 4 Recycling flow of indium from used liquid crystal display (LCD)

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