Plants to harvest rhenium: scientific and economic viability

Rhenium (Re) is one of the rarest (7 × 10⁻⁸ %) and most widely dispersed elements on Earth’s upper crust. As a consequence of its scarcity, Re is also one of the most expensive metals in the world market. Re is indeed highly demanded by the aerospace industry for the production of high-temperature superalloy turbine blades. There is a lack of study on the viability of Re phytomining. The occurrence of Re in vegetation surrounding natural and anthropogenic sources of Re suggests the ability of plants for Re accumulation and biogeochemical indication. Here we studied the aptitude of Indian mustard and scouring rush to uptake Re, in order to test the feasibility of Re phytomining. An organic substrate was spiked with KReO₄ to attain Re concentrations of 5, 10, 20, 40, and 80 mg kg⁻¹. The plants were grown for 45 and 75 days under controlled greenhouse conditions. Plant tissue samples from roots and shoots were collected in septuplicate at both harvests and analysed by atomic emission spectroscopy. Our results show high concentrations of Re in plants, ranging from 1553 to 22,617 mg kg⁻¹ at 45 days and from 1348 to 23,396 mg kg⁻¹ at 75 days for Indian mustard range. A profit of 3906 US$ ha⁻¹ harvest⁻¹ is expected from the recovered Re. Our findings thus demonstrate for the first time the scientific and economic viability of Re phytomining.