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.