[Bio-inspired Recovery of Platinum Nanoparticle and Its Mechanism]

This paper illustrated an approach of using a self-isolated bacterium Enterococcus faecalis Z5(CCTCC M2012445) to recover platinum nanoparticles from aqueous solution, and exploring its possibility under the condition of providing an exogenous electron donor. At the same time, the impacts of initial Pt concentration, biomass, temperature and pH on recovery process were researched to explore the possible mechanism of recovery process. The results showed that Enterococcus faecalis Z5 could recover platinum nanoparticles and there were two steps:bio-sorption and bio-reduction. And the initial Pt concentration 286.46 mg·L^-1, biomass 3.2 g·L^-1, temperature 50℃ and pH 6 for biorecovering were optimized. The TEM and XRD results indicated that the reduction products were platinum nanoparticles, of which most were distributed on the periplasm and the diameters were about 5 nm. Moreover, as shown by XPS figures, Pt (Ⅳ) was firstly reduced to Pt (Ⅱ), then further reduced to Pt (0) and nanoparticles were formed. The reduction of Pt (Ⅱ) to Pt (0) was a rate-limiting step. And the FTIR result showed the corresponding peaks of hydroxyl and amide group changes on the bacterium before and after reduction, probably playing an important role in the reduction process.