Fouling Characteristics and Electrochemical Recovery of Carbon Nanotube Membranes

Abstract

The fouling behavior of carbon nanotube (CNT) membranes is investigated for large protein biomolecules and a wide variety of small molecules. The CNT membranes are largely fouling resistant, even to untreated river water, due to size exclusion and an inert graphitic core that supports fast fluid flow. However, it is found that bovine serum albumin (BSA) and naphthalene significantly foul membranes due to solution coagulation and π–π stacking, respectively. Small single‐walled (SW) CNTs (<1.5 nm i.d.) are difficult to foul with BSA when precipitation is prevented, showing that size exclusion at SWCNT tips can prevent fouling. Electrochemical oxidation, bubble generation and ionic pumping are shown to recover membrane performance. Electrochemical oxidation at greater than +1.4 V is seen to oxidize CNTs as well as biofoulants, but H2 bubble generation at –2 V lifts foulants without damage to the membrane allowing for repeated cycles. Ionic pumping using large cations is seen to remove small molecule foulants adsorbed to the CNT core. The relatively narrow class of foulants and three complementary methods of membrane defouling make the CNT membrane platform a potentially robust system for a wide variety of chemical separations and environmental water treatments.

Ultrabreathable and Protective Membranes with Sub‐5 nm Carbon Nanotube Pores

“…A few previous reports investigated fouling behavior and biomolecule rejection by vertically aligned CNT pores for application in water purification. Consistently with our results for viral filtration by 3.3 nm SWNTs, these studies demonstrated complete size‐exclusion of micron‐sized bacteria and partial or complete rejection of bovine serum albumin (≈7 nm diameter) by multi‐ (MW) and SW‐ or double‐walled nanotubes, respectively. Buckypaper membranes were also reported to efficiently remove viruses and bacteria from aqueous solutions .…”

A Carbonaceous Membrane based on a Polymer of Intrinsic Microporosity (PIM-1) for Water Treatment

“…Antifouling properties of the membranes were also evaluated using bovine serum albumin (BSA) as a model foulant, which is the most commonly used protein foulant for the antifouling tests5657585960616263. Figure 3c presents the time-dependent normalized water flux variations of the NF2A, C-PIM-1, and PC-PIM-1 membranes during the filtration of a BSA solution.…”

Electrochemical wastewater treatment with carbon nanotube filters coupled with in situ generated H2O2

“…2 Among all the membrane materials, carbon nanotubes (CNTs) have been considered as a good option due to their mechanical stability, flexibility, and chemical resistivity. Previous results have demonstrated that CNT-based electrochemical filters were effective in removing aqueous organic pollutants, such as salts, 6,7 proteins, 8 viruses, 9 azo dyes, 10 pharmaceuticals, 11,12 perfluorinated chemicals, 13 and phenol. 5 An electrochemical CNT filter brings this concept one step further by not only adsorptively trapping, but also electrochemically oxidizing the target compounds.…”