Highly efficient removal of uranium from aqueous solution by a novel robust phosphonic acid functionalized aromatic-based hyper-crosslinked porous polymer

With the rapid development of the nuclear resource industry, the development of high-efficiency adsorbents is the key to the separation and removal of uranium from aqueous solutions. In this paper, phenyl phosphonic acid was designed as a functional monomer, the aromatic building blocks such as benzene and triptycene as an external crosslinker. Through the "knitting" strategy, a novel phosphonic acid-based functionalized triptycene-based hyper-crosslinked porous polymer (TPP-BPP) and benzene-based hyper-crosslinked porous polymer (B-BPP) were prepared by the above monomer and crosslinker. The resulting polymer B-BPP has a much higher surface area (S-BET = 836.21 m(2)/g) than that of polymer TPP-BPP (S-BET = 30.60 m(2)/g) due to the large skeleton triptycene confines the void. Owing to a large number of phosphonic acid functional groups, the polymer TPP-BPP and B-BPP both have a good ability to remove uranium. The optimal adsorption pH is 7 and the adsorption time is 90 min. Under the best experimental conditions, the maximum adsorption capacity of TPP-BPP for uranium is 119.05 mg/g, and the maximum adsorption capacity of B-BPP for uranium is 222.72 mg/g. Furthermore, in the presence of coexisting ions Na+, Mg2+, Al3+, Co2+, Ni2+, NO3-, CO32- etc., they still have good selectivity to uranium ascribed to the strong complexation between UO22+ and P=O groups anchored on the polymer, which was evidenced by experimental results. Also, it has good reusability and can still maintain a very high removal percentage after at least being recycled five times. Therefore, the convenient synthesis route for the novel phosphonic acid-based functionalized hyper-crosslinked porous polymer has a promising application prospect for uranium adsorption.