Effect of sodium citrate on the expansion of clay minerals during leaching process of ionic rare-earth ores

Abstract

During the leaching process of ionic rare-earth ores, the swelling of clay minerals can cause severe problems including landslides. The swelling behaviors of halloysite, kaolin, montmorillonite, and illite were investigated in this work. The regulatory mechanisms of these inhibitors on the swelling behavior of the four clay minerals were systematically studied by combining 0.20 mol/dm³ magnesium sulfate with sodium citrate solutions of different concentrations. Linear swelling experiments were conducted to measure the swelling rates of each clay mineral in sodium citrate solutions at different concentrations. Analytical techniques such as XRD, FTIR, ζ-potential measurements, and TG analysis were employed to elucidate the action mechanisms. Results indicate that when magnesium sulfate is combined with 0.02 mol/dm³ sodium citrate, the swelling inhibition rate for halloysite reaches 25.20 %; with 0.05 mol/dm³ sodium citrate, the inhibition rate for kaolin is 12.48 %; and with 0.09 mol/dm³ sodium citrate, the swelling inhibition rates for montmorillonite and illite are 18.46 % and 35.53 % respectively. This research provides a theoretical basis and technical reference for the green and efficient inhibition of clay mineral swelling during the mining process of ionic rare-earth ores.