Preparation of Several Alginate Matrix Gel Beads and their Adsorption Properties Towards Rare Earths (III)

Pure calcium alginate (CA), CA composite beads containing 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (CA-P507), core-shell structural calcium silicate-alginate (CS-A) and CS-A containing P507 (CS-A-P507) have been synthesized and their adsorption properties towards rare earths (III) have been investigated. The order of their adsorption capacities is as follows: CA-P507 > CS-A-P507 > CA > CS-A. The effect of ionic radii of rare earths on the adsorption distribution ratio has also been examined. Adsorption mechanism could mainly be proposed to be cation exchange. The pseudo-second-order kinetics model and Langmuir isotherm equation are used to describe the adsorption process very well. The adsorption capacity, selectivity and reusability have been improved owing to the introduction of P507 ionophore and CaSiO3 crust, respectively. As far as adsorption properties are concerned, CS-A-P507 is generally superior to the other three kinds of beads and shows its potential industrial application for the separation and recovery of rare earths.