Difficulties with adsorption data present in literature:
Adsorption studies often involve isotherms and report maximum adsorption capacity (qm). However, in many cases, the adsorption experiments only include a mono-element solution, making it difficult to predict the behavior of these adsorbents in a multielement solution or an actual field REEs solution (e.g., acid mine drainage, bauxite leachate). The presence of competitive ions can reduce the adsorption capacity of adsorbents for target ions by varying degrees. It is necessary for an adsorbent to retain its adsorption capacity in multielement solutions and be selective for the efficient separation of target elements. While many adsorption studies do include multi-element adsorptions, the type and concentration of competitive ions differ in different studies, making it difficult to compare the mechanism and performance of these adsorbents with each other. Even so, it should be a general practice to test the adsorbent in a multielement solution with competitive ions and actual field solutions.