Tailoring Membrane Surface Charges: A Novel Study on Electrostatic Interactions during Membrane Fouling

Abstract

Abstract:In this work we aim to show that the overall surface potential is a key factor to understand and predict anti-fouling characteristics of a polymer membrane. Therefore, polyvinylidene fluoride membranes were modified by electron beam-induced grafting reactions forming neutral, acidic, alkaline or zwitterionic structures on the membrane surface. The differently charged membranes were investigated regarding their surface properties using diverse analytical methods: zeta potential, static and dynamic water contact angle, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Porosimetry measurements proved that there is no pore blocking due to the modifications. Monodisperse suspensions of differently charged polystyrene beads were synthesized by a radical emulsion polymerization reaction and were used as a model fouling reagent, preventing comparability problems known from current literature. To simulate membrane fouling, different bead suspensions were filtered through the membranes. The fouling characteristics were investigated regarding permeation flux decline and concentration of model fouling reagent in filtrate as well as by SEM. By considering electrostatic interactions equal to hydrophobic interactions we developed a novel fouling test system, which enables the prediction of a membrane's fouling tendency. Electrostatic forces are dominating, especially when charged fouling reagents are present, and can help to explain fouling characteristics that cannot be explained considering the surface wettability.

Surface modification of the laser sintering standard powder polyamide 12 by plasma treatments

“…As can be clearly seen in Figure a, a dramatic change in the color of the PA12 powder was observed as the pristine PA12 powder is white and becomes light brown after a 1 h exposure, and a darker brown after 2 h. The treated and nontreated powders were also pressed into solid discs with the disc surface displaying a uniform color which reveals that only fewer powder particles were not well‐exposed (see Figure b). Activated atoms and molecules in the electric field during plasma exposure react with the modified surface, creating new oxygenated groups and new chemical functionalities …”

“…Different gases or gas mixtures for example, Argon or Fluorine based plasmas such as CF 4 and oxygen gas plasma, are used for the surface hydrophilisation or hydrophobisation of polymers . Plasma based technique is a common way but not the only method, other types of methods like grafting or electron beam irradiation can also be used to manipulate the surface properties of materials …”

“…[23][24][25] Plasma based technique is a common way but not the only method, other types of methods like grafting or electron beam irradiation can also be used to manipulate the surface properties of materials. [27][28][29] Several attempts have been carried out to modify a wide range of polymers using plasma for different purposes. [13,[30][31][32] Studies focused on the plasma treatment of PA12 are concentrated on the bulk material, thin films, [10,22,[33][34][35] or fibers.…”

Characteristics of coconut protein separation process by means of membrane ultrafiltration

“…Taking into account the acidic condition at pH 2.0, the molecular repulsive interaction also exited due to the evenly positive charges surrounding the protein molecules. The filtration performance was good but was slightly lower than at pH 9.0 since the ζ‐potential magnitude of the suspension was smaller (12.73 mV) (Breite et al, ; S.‐J. Hwang, Chang, & Chen, ; Luo, Vasiljevic, & Ramchandran, ; Neemann, Rosenberger, Jefferson, & McAdam, ).…”

“…The electrokinetic potential at the interface between the diffuse layer of a certain particle and its dispersion medium or the zeta (ζ)‐potential was characterized by laser Doppler electrophoresis. The sample was diluted to 0.01% (w/w) total solid and adjusted in the certain range of pH (Anagnostou, ; Azimatun Nur et al, ; Bawalan, ; Bawalan & Chapman, ; Belfort, Davis, & Zydney, ; Breite, Went, Prager, & Schulze, ; Choi, Zhang, Dionysiou, Oerther, & Sorial, ; Das, ; Garcia, Arocena, Laurena, & Tecson‐Mendoza, ; Giri & Mangaraj, ) by using 0.1 M HCl and 0.1 M NaOH solution. ζ‐Potential disposable cell containing an aliquot of the sample was placed in Nano patica SZ‐100, Horiba.…”