Selective capture scandium ions from wastewater using carbonate groups functionalized spherical aluminum phosphate

Scandium (Sc) is the most valuable rare earth element. However, it remains challenging to achieve effective separation and purification due to its low concentration as a by-product and the similarity of the coexisting metal elements. Herein, a kind of aluminum phosphate containing CO 3 2– is facilely synthesized which possesses high selectivity of Sc(III) against the competing metal ions (Ca(II), Mg(II), Ni(II), Co(II), Na(I), Zn(II), Cd(II)) and the other rare-earth ions. Notably, Aluminum phosphate can selectively capture Sc(III) over Fe(III) with a selectivity coefficient of 1.59. It also can be used to separate and purify Sc(III) from the real wastewater to obtain the purity of 99.0 % Sc(III) with the low cost. The results show that the adsorption process for Sc(III) was the single layer chemical adsorption with a maximum adsorption capacity of 273.9 mg/g. In addition, density functional theory calculations reveal that O atoms played the key role in the adsorption of Sc(III) and the addition of C atoms enhanced the adsorption between O atoms and Sc(III). This work offers a novel aluminum phosphate for the low-cost way for separation and purification of Sc(III) from wastewater.