A green chelate-like phosphate-based adsorbent functionalized by glycine (CP@Glycine) was first designed, synthesized, and applied to selectively separate Be(II) from uranium–beryllium-containing (U/Be) solutions. The optimal adsorption conditions were: W \(_\mathrm{{H_{3}PO_{4}}}\) /W \(_\mathrm{{Ca(OH)_{2}}}\) /W \(_\mathrm{{Glycine}}\) (wt/wt/wt) of 3:3:1, pH=6, resulting in the maximum adsorption efficiency of 99% in the case of adsorbent of 2 \(\hbox {g}\cdot \hbox {L}^{-1}\) . CP@Glycine exhibited excellent selectivity for Be(II) ( \({K}_\text{d}={2.53 \times 10^{4}}\,{\hbox {mL}\cdot \hbox {g}^{-1}}\) ) toward Fe, U, Zn, Mn, Na, and Ca in solutions. After 5 adsorption–desorption cycles, the removal efficiency of Be(II) remained at 85%, and the desorption rate of Be(II) was above 90%. Adsorption kinetics and thermodynamics studies showed that the theoretical maximum adsorption capacity (Q \(_\text{e}\) ) of CP@Glycine was 66 \(\hbox {mg}\cdot \hbox {g}^{-1}\) , which was higher than the state-of-the-art adsorption materials. Besides, the surface of CP@Glycine exhibited abundant active sites with negative charges which would have a potential electrostatic attraction with Be(II). Moreover, the adsorption mechanism of CP@Glycine was methodically revealed through a combination of various characterizations and DFT investigations. It was found that BeNH \(_{4}\) PO \(_{4}\) and Be(OH) \(_{2}\) were formed as stable precipitates on the surface of CP@Glycine, which implied that Be(II) was coordinated with the amino and the phosphate groups from CP@Glycine, thus achieving the chelation effect of Be(II) with CP@Glycine for the adsorption process. The results of DFT investigations further confirmed that Be(II) owned strong bonding affinity to the amino group and the phosphate group from the as-prepared CP@Glycine. The results indicated that the calculated binding energy of the Be complex coordinated with glycine and phosphate ( \(-\) 229.37 \(\hbox {kcal}\cdot \hbox {mol}^{-1}\) ) was lower than that of other possible Be complexes. The above findings revealed that CP@Glycine could be a promising adsorbent for the selective separation and recovery of Be(II) from U/Be wastewater.
