UV pre-activation/thermal initiated grafting of caffeic acid on PVDF for preparation of adsorptive membranes for cesium

Caffeic acid(CA) was grafted on PVDF by UV pre-activation/thermal initiated grafting method with PVDF solution as substrates for the first time. The PVDF-g-CA was employed for fabrication of adsorptive membranes for cesium, and the static and dynamic adsorption, along with elution and membrane reusability, were studied. The results show that, under the same concentrations and grafting time, the average grafting degree of UV preactivation/thermal initiated grafting method is much higher than that of the two-step UV grafting and the one-step UV grafting. The PVDF-g-CA membranes show high adsorption capacity for Cs+(0.23 mmol/g, 25 degrees C), and the selectivity factor of Cs+ vs. Li+, Na+ and K+ is 8.46, 3.68 and 3.23. This is the first report about the selective adsorption of Cs+ by CA-based materials. The adsorption isotherm can be well described by the Langmuir model. The membrane can be reused for 4 times without apparent performance deterioration, indicating great potential in adsorption of cesium from aqueous solutions.