[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.