2．白金族金属・金のバイオミネラリゼーション

生物による固体物の生成がバイオミネラリゼーションであり、その身近な例が貝殻、サンゴである。


2．1　白金族金属イオン，金イオンのバイオ還元・析出

2．2　リサイクル技術としての特徴と課題

2．3　貴金属ナノ材料の新規調製法としての展開

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We found that the metal ion-reducing microorganism, Shewanella algae (Figure 1), exhibit the ability to reduce and deposit the precious metal ions of gold (III), platinum (IV), palladium (II), and rhodium (III) into metal nanoparticles, a process known as biomineralization (Figure 2). We have collected fundamental data demonstrating that the ability of these microorganisms can be applied to the recycling of precious metals (Ogi e al., 2010a, 2010b, 2011a, 2011b; Konishi et al., 2007a, 2007b, 2007c; Tamaoki et al., 2010). In addition, when targeting the leachates from printed circuit boards, the metal ion-reducing microorganism can successfully allow selective reduction and deposition of gold ions under acidic conditions (pH 1-2) in the presence of heavy metal ions such as copper, proposing a new bio-recovery system of gold (Figure 3). Compared to existing recycling methods, the new bio-recycling method has the following features:

  • Enables a multi-step process of nanoparticle synthesis via separation and concentration of a precious metal in dilute solution to be accomplished in a single step;
  • The bio-reduction and bio-precipitation is completed rapidly at room temperature (within 30 minutes for batch operation);
  • An energy-saving recovery method with a low environmental load and functioning as a high value-added recycling process for the room temperature synthesis of metal nanoparticles.

Introducing biotechnology into the process of recovering precious metals from urban mining is directed at building a foundation for the development of eco-friendly material recycling technologies: 1) we will construct an integrated system comprising the separation and concentration processes of precious metal from the leachates of the post-consumer products and the conversion process into highly functional precious metal materials in the form of nanoparticles; 2) in order to put the system into practical use, we will carried out a proof test with a small scale demonstration system (Mini plant).


Figure 1 Precious metal ion-reducing bacterium

 


Figure 2 TEM images of S. algae bacteria and palladium nanoparticles

 


Figure 3 Recycling flow of precious metals by the new and conventional technologies

 

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