Platinum is one of the rarest and most valuable metals in the world.
Thanks to its physical and chemical properties platinum has become a key component for the functioning of our society. One of the reason that platinum is so valuable is that it occurs in very low concentrations and associated to other metals.
Because of this, there are only a few mines in the world that are profitable to exploit. And since recycling methods are not very developed, it is only a question of time until mining is no longer a solution.
Unfortunately, predictions state that all known economically workable platinum deposits will be exhausted in 2064. Platinum shortage could have great socioeconomic consequences.
As an initiating step towards solving this issue we decided to design a novel method of recycling platinum from an unexploited source — soil next to highways.
Many studies have shown that there are great quantities of platinum deposited in the soil next to roads, often in higher concentration than in mines.
The reason for this accumulation is the constant automobile traffic.
Indeed, platinum is present in the catalytic converters of cars and trucks and it is released progressively in the exhausts. Therefore the platinum accumulates around the traffic routes, on asphalt, in soil, even in plants.
Our goal is to concentrate platinum as much as possible. We decided to do it in two distinct steps.
The first step relies on the affinity of siderophores to bind solubilized Platinum atoms and, thus, favor the further solubilisation of more platinum compounds. We accomplish this by inserting a plasmid containing the four enzymes (Des A, Des B, Des C, Des D) necessary to synthesise our siderophore — Desferrioxamine B, into E. coli.
At a second level, we plan to use the principle of biosorption. A modified FliC protein complex will be cloned into E. coli and enable the flagella of the bacterium to bind platinum atoms. This specificity will be possible thanks to a peptide that will be inserted into the sequence of the FliC protein.
The benefit of using the biosorption is to obtain nanoparticles of platinum, a highly valuable form of the metal.