“…Functional ligands grafted on the silica gel for REEs adsorption are 4-acylpyrazolone Schiff base (Amarasekara et al, 2009), diglycolamic acid (Ogata et al, 2014(Ogata et al, , 2015a(Ogata et al, , 2015b(Ogata et al, , 2016, 1-(-2-pyridylazo) naphthol (PAN) , acetylacetone , phosphonoacetic acid (PAA), N, N-bis(phosphonomethyl) glycine (BPG), diethylenetriaminepentaacetic dianhydride (DTPADA) (Callura et al, 2018;Noack et al, 2016), diethylenetriaminepentaacetic acid (DTPA) (Noack et al, 2016), diglycolamide (Zhe Liu et al, 2019) N-Benzoyl-N-phenylhydroxylamine (BPHA) (Artiushenko, Ávila, et al, 2020), amino-di(methylene-phosphonic) acid (Artiushenko, Kostenko, et al, 2020), N, N-dioctyldiglycolic acid (DODGA) (Li et al, 2020), polyhexamethylene guanidine and Arsenazo I or Arsenazo III (Losev et al, 2020), and bis(ethylhexyl)amido diethylenetriaminepentaacetic acid (Hovey et al, 2021).…”