| Summary: | Rare earth oxides such as La<sub>2</sub>O<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub> are abundant in waste optical glass. The separation of rare earth oxides is beneficial to the recycling of rare earth resources. In this study, the rare earth oxide Gd<sub>2</sub>O<sub>3</sub> particles were separated from La<sub>2</sub>O<sub>3</sub> particles using high gradient magnetic separation, and the influence of different fluid media (i.e., water, anhydrous ethanol, and their mixture) on the separation results was investigated. By using the measured zeta potential of oxide particles in water/ethanol of different pH and water with different dispersants (Na<sub>2</sub>SiO<sub>3</sub> 9H<sub>2</sub>O, citric acid, Na<sub>2</sub>CO<sub>3</sub>, and sodium hexametaphosphate), the DLVO (Derjaguin–Landau–Verwey–Overbeek) potential calculations and their analysis applied to high gradient magnetic separation results were also performed. The results showed that using anhydrous ethanol or adding a dispersant in water as a fluid medium can promote the separation of magnetic Gd<sub>2</sub>O<sub>3</sub> particles under a high-gradient magnetic field. Among the different conditions, anhydrous ethanol can improve the grade of Gd<sub>2</sub>O<sub>3</sub> to 95% from 70% with water. Furthermore, ethanol can be reused after filtration, making it an environmentally friendly fluid medium. Among the four dispersants, sodium hexametaphosphate, Na<sub>2</sub>SiO<sub>3</sub>, and Na<sub>2</sub>CO<sub>3</sub> can also increase the separation rate of La<sub>2</sub>O<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub> to about 95%. The effect of citric acid on the separation performance is slightly worse, and the recovery rate of Gd<sub>2</sub>O<sub>3</sub> is 80%. This study provides a new reference for selecting a fluid medium for magnetic separation.
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