Effect of surfactant addition on leaching process of weathered crust elution-deposited rare earth ores with magnesium sulfate

Surfactants were proposed to be added into magnesium sulfate solution to improve the leaching process of weathered crust elution-deposited rare earth ores (WREOs). Effects of surfactants and their concentration on the seepage of leaching solutions and the leaching efficiency of rare earth (RE) and aluminum (Al) were investigated, and the leaching kinetics, the mass transfer process, the adhesion work and the adhesion work reduction factor were analyzed to reveal its strengthening leaching mechanism. The results show that cetyltrimethylammonium bromide (CTAB) has a better strengthening effect on the leaching process than dodecyl trimethyl ammonium bromide (DTAB), sodium dodecyl sulfate (SDS), sodium oleate and oleic acid. In the presence of 0.04% CTAB in 0.2 mol/L solution, the permeability coefficient of WREOs increases from 0.945×10−5 to 1.640×10−5 cm·s−1, and the leaching efficiency of RE increases from 80% to 90%, confirming the promotion of surfactants on the leaching process of WREOs. Kinetic analysis shows that the leaching process conforms to the inner diffusion control model, and the leaching kinetics equations of RE and Al related to CTAB content are obtained. Mass transfer discussion shows a smaller height equivalent to theoretical plate (HETP) of RE and Al at CTAB content of 0.04%, suggesting the higher mass transfer efficiency here. According to the interfacial properties of leaching solutions, the calculated adhesion work and the adhesion work reduction factor further demonstrate the strengthening leaching effect of CTAB on the leaching process of WREOs.