[Adsorption characteristics of Cu2+ onto the polyvinylidene fluoride blending modified membrane]

Using the combination method of thermally induced polymerization technique and phase inversion blending process, a novel polyvinylidene fluoride (PVDF) blending modified membrane with ion-exchanging property, was prepared. The PVDF modified membrane was characterized by XPS, XRD, SEM and FTIR. The adsorption property, adsorption isotherm and batch sorption kinetics of Cu2+ by the PVDF modified membrane were studied. The results indicate that the adsorption processes for Cu2+ are found to follow the pseudo-second-order kinetics equation. And the isotherm of adsorption of Cu2+ by the modified membrane is good agreement with that of Langmuir isotherm model. The values of the mean free energies of the adsorption process are found to be between 8 and 16 kJ/mol, which shows that the adsorption mechanism of the PVDF modified membrane is an ion-exchange process. The value of deltaH0 is > 0, deltaG0 is < 0, and deltaS0 is > 0, which shows that the adsorption of the PVDF modified membrane is a spontaneous and endothermic process. The experimental data also show that the PVDF modified membrane possesses an excellent adsorption/desorption property. The adsorption capacity of Cu2+ onto the modified membrane in the synthesized Cu2+ solution and the sewage water is more than 0.025 mg/cm2 and 0.015 mg/cm2, respectively, and its desorption efficiency is still beyond to 95%, after four adsorption/desorption processes. It can be found that the PVDF modified membrane can be reused almost without any significant loss in the adsorption performance. PVDF modified membrane can be used for the recovery of metal traces and polishing of treated effluents containing heavy metals.