Production of metals and oxygen from coal fly ash by aluminothothermic and electrochemical reduction process

In-situ utilization of lunar resources for the production of metals and oxygen is essential for lunar exploration. The main emphasis of this article is on a candidate approach that combined aluminothermic reduction and electrolysis process in cryolite molten salts to produce both Al-based alloy and oxygen from lunar soil simulants. The influences of reductant amount and reaction time on the aluminothermic reduction of coal fly ash in cryolite melts at 1233 K (960 °C) were studied. The results obtained by XRF, XRD, SEM and EDS analysis show that the products mainly contain Al, Si, Fe, and little Ti, while the main phases of the products are Al and Si. With the increase of reaction time, the content of Si in alloy products increases from 4.43 wt% to 7.47 wt%. In addition, the remaining alumina-rich cryolite melts was electrolyzed at 1233 K (960 °C) using 56 wt%Fe-44 wt%Ni alloy inert anode. The cathode product obtained by galvanostatic electrolysis for 4 h was characterized, and the results showed that the phase composition of the cathode product was pure Al, while the highest aluminum content in the cathode product is 99.431 wt%. Besides, the outlet gas at the anode during electrolysis is pure oxygen according to the analysis of gas chromatography.