Enhanced uranium uptake from acidic media achieved on a novel iron phosphate adsorbent

By combining phosphoric acid precursor synthesis and co-precipitation method, we developed a facile approach for synthesizing iron phosphate (FeyPz) with repeatable technique and low economic cost. The procedure begins with synthesis of P-doped carbon dot (pCD), followed by introducing the pCD in the preparation condition of Fe3O4. Interesting, the uranium(U(VI)) adsorption capacity of FeyPz is significantly influenced by the synthesis conditions of FeyPz and the optimized performance can be achieved by tuning the functional groups and structure of FeyPz. Compared to the FePO4٠2H2O and Fe3O4, the FeyPz-10 showed 3561% and 684.5% enhanced performance in U(VI) uptake, respectively. The maximum adsorption capacity of FeyPz-10 based on Langmuir model could reach up to 1.22 mmol g−1 at pH 4.5, which was comparable with the saturated adsorption capacity based on Thomas model with its value of 0.87 mmol g−1, that was higher than some of adsorbents reported previously. In addition, the adsorbent had a superior reusability and still kept up high adsorption capacity for U(VI) after 5th cycle. Moreover, an adsorption-reduction mechanism was proposed and XPS analysis confirmed the outstanding adsorption capacity for U(VI) on the adsorbent was mainly ascribed to the transformation of Fe2+ to Fe3+ on FeyPz-10 that results in U(VI) reduction.