Rapid and selective recovery of heavy rare earths by using an adsorbent with diglycol amic acid group

• We synthesized the adsorbent with immobilized diglycol amic acid on the silica gel.
• The adsorbent has high adsorption–desorption rate for practical application.
• The adsorbent recovered rare earths from high concentration solutions of base metals.
• The adsorbent enriched heavy rare earths 10- to 20-fold from even dilute solutions.

The recovery of rare earths from ores and scraps requires the selective separation of dilute rare earth ions from solutions containing high concentrations of base metal ions. Using column tests under conditions mimicking practical use, we investigated a novel adsorbent comprising silica gel particles modified with diglycol amic acid groups (EDASiDGA). We evaluated the influence of flow rate on dysprosium adsorption–desorption behavior and the selective adsorption of dysprosium ions from a simulated solution containing dilute rare earth ions and high concentrations of base metal ions at low pH (pH 1.0). The EDASiDGA-packed column had a high adsorption–desorption rate. Moreover, the EDASiDGA-packed column enriched middle and heavy rare earths more than 10- to 20-fold from even a dilute solution. In addition, the molar ratios of the rare earths to base metals in the solution after desorption were three to four orders of magnitude higher than the initial molar ratios.