Study on the adsorption-desorption behaviours of La3+, Sm3+, and Y3+ by HEHEHP extraction resin in chloride medium

The adsorption-desorption behaviours of La3+, Sm3+, and Y3+ on 2-ethylhexylphosphonic acid mono-2-ethyl hexyl ester (HEHEHP) extraction resin were investigated in a chloride medium. The effects of reaction time, pH, hydrochloric acid concentration, flow rate, and adsorption mechanism were studied in detail using static and dynamic experimental methods. The results show that La3+ is the first to reach adsorption equilibrium, followed by Sm3+ and Y3+; the highest adsorption capacities of La3+, Sm3+, and Y3+ are obtained at solution pH of 4 and in the order of Y3+ > Sm3+ > La3+. La3+, Sm3+, and Y3+ can be eluted by 0.3, 0.5, and 3 mol/L hydrochloric acid, respectively, indicating that La3+ elutes most easily, and Y3+ is difficult. Moreover, the flow rate has little effect on the peak of rare earth desorption. The adsorption process is chemisorption; the slope method indicates that for each mol Sm3+ or Y3+ ion adsorbed, 3 mol H+ ions are simultaneously released, but two for La3+ under the given pH conditions. It is expected to provide theoretical and technical support for preparation of ultra-high purity rare earth by HEHEHP extraction resin.