QCM-D与AFM联用解析EfOM在SiO2改性PVDF超滤膜表面的吸附机制

为了进一步从微观角度上研究不同过滤阶段出水有机物(Ef OM)在纳米Si O2改性超滤膜表面的具体吸附机制,通过调节Si O2添加比例从而获得不同改性程度的实际膜.借用耗散型石英晶体微天平(QCM-D)与原子力显微镜(AFM)联用技术分别测定Ef OM在膜表面的吸附情况和Ef OM与膜之间的相互作用力.QCM-D实验结果与分析表明,膜表面的亲水性越好,膜表面Ef OM吸附量就越少,以及Ef OM在膜表面的吸附速率明显减缓.实验结果还发现,Ef OM的吸附经历了两个阶段:在初始阶段(15 min内),有机物快速吸附到膜表面并堆积;当Ef OM的吸附频率达到平衡时,耗散却处于非平衡状态,该现象说明虽然Ef OM在膜表面的吸附量达到稳定,但其吸附层的构象却仍在发生变化.AFM测定结果证明,随着亲水性的不断改善,Ef OM-膜、Ef OM-Ef OM之间的作用力均有所减小,该结果揭露了膜面Ef OM吸附量减少吸附速率下降的本质原因.QCM-D与AFM的联用有效地解释了膜改性对Ef OM吸附机制的影响.

Adsorption Mechanisms Analysis of EfOM on PVDF Ultrafiltration Membranes Modified by SiO2 Using QCM-D and AFM

To further unravel adsorption mechanisms of effluent organic matter (EfOM) on the PVDF ultrafiltration membranes modified by nano-silica particles from micro perspective during different filtration phases, the membranes were prepared by adjusting the dosage of nano-silicon. The adsorption of EfOM on the surface of the membranes and the interaction between EfOM and the membranes were measured by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM).The QCM-D results suggested that adsorbing capacity and adsorption rate of EfOM on the hydrophilic surfaces were lower than on the hydrophobic surfaces. Meanwhile, it was found that EfOM underwent adsorption via two steps: In the initial 15 min stage, a rapid adsorption of EfOM accumulated onto the membrane surface; The change in dissipation still occurred when the EfOM adsorption frequency reached balance, which demonstrated that the adsorption of EfOM remained unchanged on the membrane surfaces, and changes in the conformation of adsorption layer still occurred. For the AFM force test, it was found that the EfOM-membranes and EfOM-EfOM interactions declined with the increase of hydrophily, which revealed the essential reason for the decrease of adsorbing capacity and adsorption rate. The combined utilization of QCM-D and AFM effectively explained the effect of modified membranes on adsorption mechanisms of EfOM.