高效选择性除铯的PVDF复合膜制备及优化

为实现对放射性核素铯（Cs）的高效去除，本研究基于表面接枝技术利用均苯三甲酰氯（TMC）在羟基化的PVDF微滤/超滤膜表面接枝了一层氨基化SiO₂，并通过SiO₂表面的氨基基团与Fe³⁺结合实现亚铁氰化铁（Ferrocyanide，FeCN）的负载，从而制备了FeCN/SiO₂/PVDF复合膜.基于膜表面的SEM与XPS表征考察了氨基化SiO₂的不同负载条件，研究发现粒径和浓度分别为300nm及0.4%时可实现SiO₂的最大负载量.对比不同亚铁氰化铁负载量下复合膜的水通量和Cs去除率，结果表明对微滤平板膜进行3次负载后过滤效果最好，可实现99.6%以上的Cs去除率，且XPS结果表明强酸及超声条件下该复合膜仍然具有良好的稳定性.复杂水质条件下的过滤实验表明，过滤前期由于对吸附点位的竞争使得溶液中共存离子半径与Cs越接近其对Cs截留率的影响越大；过滤后期在道南作用的影响下，随着共存离子水合离子半径提高，其对Cs的去除率的影响越大；天然有机质对水通量影响较大，对Cs去除率影响弱于共存离子.

Preparation and optimization of PVDF composite membrane for efficient and selective removal of radioactive cesium

In order to achieve the efficient removal of radionuclide cesium (Cs), the FeCN/SiO₂/PVDF composite membrane was prepared through the surface grafting between amino functional groups of SiO₂ and Fe³⁺, after SiO₂ coating on the hydroxylated PVDF membrane. Loading dosage and particle size of SiO₂ were optimized by SEM and XPS analysis to be 0.4% and 300nm, respectively. The Cs removal rate was improved to be more than 99.6% after three times loading of the composite membrane. In addition, XPS results illustrated that the prepared membrane was stable even under strong acid and ultrasound conditions. In the complicated water solution, the coexisting cations competed with Cs adsorption when their hydrated ionic radius were similar in the early stage of filtration. In the later stage, the extent of Cs removal rate decline was positively correlated with the ion radius of coexisting cations due to the influence of Donnan effect. Additionally, natural organic matter (NOM) had a larger effect on water flux, whereas had a weaker effect on Cs removal than that of coexisting cations.