Simultaneous ex-situ CO2 mineral sequestration and hydrogen production from olivine-bearing mine tailings

摘要

Hydrothermal alteration batch experiments were conducted on olivine bearing mine tailings in order to investigate two potential valorization methods: the ex-situ CO2 sequestration and hydrogen production. The originality of this work lies in the simultaneous investigation of these two processes. We reacted powdered mine tailings with CO2-saturated water at three different sets of P/T conditions, 473 K/15 MPa, 523 K/30 MPa and 573 K/30 MPa. After 25 days of reaction, CO2 was sequestered in the form of Fe-bearing magnesite, (Mg,Fe)CO3 in all the experiments. Maximum carbonation yield was achieved at 523 K and 30 MPa, which was 53.8 wt% of product, equivalent to the trapping of 320.5 g of CO2 per kg of mine tailings. Hydrogen gas was produced via the oxidation of Fe2+ in olivine. The highest quantity of hydrogen (H-2) was produced at 573 K/30 MPa which was 0.57 g of H-2 per kg of mine tailings. It suggests that the temperatures between 523 K and 540 K at pCO(2) = 30 MPa are favorable for simultaneous ex-situ CO2 mineral sequestration and hydrogen production from New Caledonian mine tailings.