Development of functionalized doped carbon nanotube/polysulfone nanofiltration membranes for fouling control

Abstract

This work describes the fabrication of nitrogen doped and phosphorus doped carbon nanotube (fP-CNT and fN-CNT)/ polysulfone blend membranes via a phase inversion method. The structural morphology, hydrophilicity, rejection, and permeability properties of the blend membranes were found to be dependent on the amount and type of functionalized CNTs (fCNTs) incorporated (i.e., fN-CNTs, fP-CNTs). The results showed that PSf membranes modified with P-or N-doped CNTs have significantly improved hydrophilicity, thermal stability, water uptake, and surface charge compared to membranes modified with pristine fCNTs. Scanning electron microscopy studies demonstrated that the addition of the doped CNTs resulted in the formation of 'finger-like' structures subsequently leading to increased membrane porosities and pore sizes. Thus, doped CNTs imparted on the transport mechanism of the parent membranes resulting in enhanced flow rates and better selectivity. This increase could be due to a combination of steric limitations from the carboxylic functional groups present in their surfaces leading to electrostatic repulsions between functional groups present in the membranes and the humic acid molecules.

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

“…[3][4][5][6] Currently, commercially available purification and recovery techniques for this approach are gas sweetening, swing adsorption, amine treating, and cryogenic procedures, which have high costs and high energy use. [7][8][9][10] Within the last few years, researchers have been greatly interested in synthesizing novel membranes for gas-separation systems. High efficiency and productivity and low consumption of energy are regarded as the most important objectives in designing such systems.…”

“…Among the polymeric precursors in the preparation of composite membranes, polysulfones and polyimides are the most fascinating because of their excellent properties, such as high productivity and efficiency of separation, high thermal and chemical stability, high mechanical resistance, and ease of preparation. 8,[60][61][62][63][64] They tend to have the highest gas transport properties of the polymer families, but even the best solution polymeric membranes are limited by an upper bound of possible gas selectivity and permeability. The high gas selectivity, combined with a relatively high gas permeability, allows many of these membranes to operate above the upper bound.…”

A novel conductive membrane with RGO/PVDF coated on carbon fiber cloth for fouling reduction with electric field in separating polyacrylamide

“…Electricity conductive composite membranes could be prepared by loading carbon nanotube on membrane surface or blending in polymer casting solution . The blended polysulfone membrane had nitrogen doped or phosphorus‐doped carbon nanotube which negatively charged the surfaces of composite membrane, increased salt rejection, and antifouling resistance . Conductive bases such as carbon fiber cloth or stainless‐steel mesh had been used in preparing conductive membrane, by coating PVDF and conductive polymers onto it to improve the filtration property.…”

“…Thus, intensive and extensive methods studies about membrane fouling reduction had been conducted, [6][7][8] including the use of electric field. [9][10][11][12][13][14][15][16][17][18][19][20][21] The energy cost of using high-intensity electric field in ultrafiltration is higher 9,10 than using low-intensity minute electric field.…”

“…13,14 The blended polysulfone membrane had nitrogen doped or phosphorus-doped carbon nanotube which negatively charged the surfaces of composite membrane, increased salt rejection, and antifouling resistance. 15 Conductive bases such as carbon fiber cloth or stainless-steel mesh had been used in preparing conductive membrane, by coating PVDF and conductive polymers onto it 16,17 to improve the filtration property. Nonconductive nonwoven filter/cloth had also been used and modified with conductive polymers (polyaniline, polypyrrole), 18,19 and graphene doping further improved the conductivity.…”