Efficient Recycling of High-grade Concentrate Powders from Feldspar Slime Using Mechanochemically Assisted Acid Leaching

Feldspar beneficiation produces large amounts of slime waste, which should be efficiently recycled to achieve the economic and environmental benefits. In this study, mechanochemically assisted acid leaching (MAL) was employed to efficiently recycle high-grade concentrate powders, and the physically beneficiated powder from feldspar slime was initially used as a feedstock to reduce gangue mineral disturbance. Milling time and leaching parameters were investigated to reveal their effects on the mass recovery and whiteness of concentrate powders, and the purification mechanism was clarified by chemical reactions and leaching kinetics. The colored minerals were partially liberated and removed by the mechanochemical treatment and further reduced by acid leaching. The optimal MAL process consists of 2 h milling of the feedstock powder in the 5% HCl solution and acid leaching at 95 °C for 4 h. When the feldspar slime was beneficiated by the combination of magnetic separation and MAL, the mass recovery of the ultrafine (0.72 μm) concentrate powder was 76.7%, with a grade of 0.10% Fe₂O₃. The whiteness’s of the powder and the burnt sample were 91.2% and 64.3% respectively. This facile processing route enables commercial recovery of high-grade concentrate powders from feldspar slime, thus promoting sustainable exploitation of feldspar resources.