The potential of ultrasonic pretreatment enhancing selective surface dissolution to improve the floatability of spodumene with different size fractions was verified and investigated. For coarse particles of −0.15 + 0.0385 mm, compared with traditional pretreatment methods, ultrasonic pretreatment could optimize the physicochemical properties of the surface, markedly increased the amount of NaOL adsorbed on the mineral surface, and improved the floatability of the spodumene. For fine particles of −0.0385 mm, both pretreatment methods (Ultrasonic and Traditional) could greatly increase the flotation recovery, but ultrasonic pretreatment had no obvious advantage compared with traditional method. ICP combined with XPS analysis were conducted to investigate the dissolution mechanism of spodumene surface in different pretreatment system. Si species on the surface of coarse particles were easily dissolved into the solution under the effect of ultrasound, which increases the relative content of Al and Li species on the surface. This was conducive to the adsorption of the collectors on the surface. However, the selective dissolution of the fine particle surface was weakened by excessive energy intake in the ultrasonic system, which neutralized the advantage brought by the large amount of dissolution, making the results obtained by the two preprocessing methods the same.

Surface dissolution behaviors of spodumene, feldspar, and quartz, and its influences on their surface properties and flotation separation were investigated when pretreated in deionized water (DI water), NaOH solution and HCl solution individually. The surface components of minerals, such as Si and Al, had shown different dissolution behaviors. In the presence of sodium oleate, the contact angle of spodumene increased after pretreated by the NaOH solution, but it decreased after pretreated by the HCl solution. The dissolution of Si from spodumene is helpful to the adsorption of sodium oleate and the flotation separation of spodumene from silicates, but the dissolution of Al has the opposite effect.

This study investigates the negative impact of temperature on spodumene flotation from the perspective of the gas–liquid interface of sodium oleate (NaOL) solutions. Micro-flotation tests revealed a significant decrease in the flotation recovery of spodumene when NaOL was employed as a collector, dropping from 55.3% at 305.4 K to 5.1% at 277.3 K as the temperature decreased. A strong linear correlation between the surface tension of the NaOL solution and temperature was established. As the temperature decreased, the surface tension of 6 × 10⁻⁵ mol/L NaOL increased from 37.88 mN/m at 294.9 K to 40.71 mN/m at 281.9 K, while its critical micelle concentration decreased from 9.49 × 10⁻⁴ mol/L at 305.0 K to 6.85 × 10⁻⁴ mol/L at 288.0 K. Additionally, molecular dynamics (MD) simulations indicated that a decrease in temperature resulted in an enhancement of intermolecular action forces, a more compacted interfacial structure, and weakened molecular thermal motion at the gas–liquid interface of the NaOL solution. These variations were found to be the main reason for the rise in the surface tension of the NaOL solution as the temperature decreased, which in turn lowered its efficiency, resulting in a decrease in the flotation efficiency of spodumene.