This study investigated the desorption characteristics of red mud and loess with an optimum mass ratio (RM-L73) loaded with Mn²⁺ and Cd²⁺ in neutral and acidic environments through batch desorption tests. The desorption mechanism was clarified by understanding the capture mechanism of RM-L73 and establishing desorption isotherms. Furthermore, the effect of coexisting ions on RM-L73’s removal efficiency was examined by batch adsorption tests. Results indicate that the -OH groups in RM-L73 play a substantial role in capturing Mn²⁺ and Cd²⁺ from acidic wastewater and considerably enhance the adsorption effect of RM-L73. Additionally, Cd²⁺ was more sensitive to environmental pH levels than Mn²⁺, and a desorption distribution coefficient was introduced to characterize the ease of desorption. Coexisting ions had antagonistic effects on the removal of Mn²⁺ and Cd²⁺. The inhibitory effect generally intensified with increasing initial concentration of Cd²⁺. However, the inhibitory effect on Mn²⁺ could be mitigated at high concentrations. Cu²⁺ significantly reduced the adsorption capacity of RM-L73 for Mn²⁺ and Cd²⁺, with a stronger effect on Mn²⁺.