Microwave assisted synthesis of phosphorylated PAN fiber for highly efficient and enhanced extraction of U(VI) ions from water

In the present study, a phosphorylated polyacrylonitrile (PAN) fiber adsorbent was rapidly prepared with microwave (MW) assisted method and further applied to capture U(VI) ions from aqueous solution. FTIR and SEM/EDS characterizations confirmed the satisfactory grafting of phosphonic group on the surface of PAN fiber and the integrities of fiber were well preserved. The results indicated that MW assisted method exhibited much higher efficiency during the modification process in terms of shorter reaction time and higher phosphonic content as compared to conventional heating method. The physical property of the modified fiber was well maintained according to TGA/DTA results. The kinetic and isothermal adsorption experiments confirmed that the uptake process of PAN,Phos fibers for U(VI) followed both pseudo-second-order and Langmuir model, indicating that the adsorption process was controlled by chemisorption mechanism. The maximum adsorption amount for prepared adsorbent towards U(VI) reached at 241.4 mg/g based on the Langmuir calculation, which was relatively higher than other fibrous adsorbent. Moreover, the functional fiber (PAN(MW)-Phos) revealed selective adsorption ability for U(VI) from solution that contained multiple competing metal ions in pH range of 3.0-6.0. Thermodynamic adsorption results further verified the spontaneous and endothermic nature of the binding process. Additionally, the PAN(MW)-Phos showed satisfied desorption and reusability in five times application. The effective extraction of U(VI) ions was mainly attributed to the inner surface complexation mechanism between phosphonic groups and U(VI) ion. The feasible preparation method, higher capacities, excellent selectivity and promising recyclability endow the phosphorylated fiber as suitable adsorbent for extraction of U(VI) from aqueous solution.