Oil Deposition on Polymer Brush-Coated NF Membranes

Abstract

Membrane-based processes are attractive for treating oily wastewaters. However, membrane fouling due to the deposition of oil droplets on the membrane surface compromises performance. Here, real-time observation of the deposition of oil droplets by direct confocal microscopy was conducted. Experiments were conducted in dead-end and crossflow modes. Base NF 270 nanofiltration membranes as well as membranes modified by grafting poly(N-isopropylacrylamide) chains from the membrane surface using atom transfer radical polymerization were investigated. By using feed streams containing low and high NaCl concentrations, the grafted polymer chains could be induced to switch conformation from a hydrated to a dehydrated state, as the lower critical solution temperature for the grafted polymer chains moved above and below the room temperature, respectively. For the modified membrane, it was shown that switching conformation of the grafted polymer chains led to the partial release of adsorbed oil. The results also indicate that, unlike particles such as polystyrene beads, adsorption of oil droplets can lead to coalescence of the adsorbed oil droplets on the membrane surface. The results provide further evidence of the importance of membrane properties, feed solution characteristics, and operating mode and conditions on membrane fouling.

Oily Wastewater Treatment Using Polyamide Thin Film Composite Membrane Technology

“…At the membrane surface, permeate flow rate reduces with time and concentration polarization increases. A decrease in flux was recorded as a result of increased mass transfer resistance, so fouling is often considered in the form of decreasing permeate flux over time [45][46][47][48][49]. Membrane blocking leads to a decrease in membrane performance because of suspended solids accumulating on the outer layer.…”

Atomic Layer Deposition for Gradient Surface Modification and Controlled Hydrophilization of Ultrafiltration Polymer Membranes

“…The experimental setup is shown schematically in Figure . A custom-made crossflow filtration cell, with a sapphire glass viewing port, allows in situ observation using a confocal laser scanning microscope (TCS SP8, Leica Microsystems). − Channel dimensions within the cell are 0.6 mm ( H ), 6 mm ( W ), and 36 mm ( L ) with a total membrane filtration area of 216 mm 2 . The flow cell was mounted on the microscope stage, and imaging was made with a 25× water immersion objective with a numerical aperture of 0.95, corresponding to a 262 144 pixel (384 400 μm 2 ) field of view.…”

Advanced stimuli-responsive membranes for smart separation

“…In recent years, researchers have turned to stimuli-responsive materials as a novel approach to improving membrane surface properties for reducing fouling. [227][228][229] These functional materials not only modify surface characteristics but also change morphologies in response to environmental stimuli. The self-regulated surface structure of the membranes promotes the elimination of contaminants clinging to the membrane surface and endows the membranes with self-cleaning capability.…”