Unlocking the potential of polymeric desalination membranes by understanding molecular-level interactions and transport mechanisms

Nickerson, Trisha; Antonio, Emma N.; McNally, Dylan P.; Toney, Michael F.; Ban, Chunmei; Straub, Anthony P.

doi:10.1039/d2sc04920a

Cited by 16 publications

(3 citation statements)

References 146 publications

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“…iodide and bromide, have served as an important set of systems to study the fundamental mechanisms of Charge-Transfer-To-Solvent (CTTS) dynamics. They are highly relevant for solvation studies due to their natural abundance and role in cell biology [21][22][23] and cloud formation. 24 A prevailing perspective has long been that upon excitation with a photon, the electron abstracted from an aqueous halide rst exists in close proximity to its original atom (a so-called contact pair), before it becomes hydrated and dissolves into the solvent as a free electron.…”

Section: Introductionmentioning

confidence: 99%

Real-time structural dynamics of the ultrafast solvation process around photo-excited aqueous halides

Markmann,

Pan,

Hansen

et al. 2024

Chem. Sci.

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Section: Introductionmentioning

confidence: 99%

Real-time structural dynamics of the ultrafast solvation process around photo-excited aqueous halides

Markmann,

Pan,

Hansen

et al. 2024

Chem. Sci.

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“…Although strong oxidants have the potential to enhance membrane performance, materials commonly used in salt-rejecting membranes, such as polyamide and cellulose acetate, degrade when exposed to strong oxidizing agents such as chlorine and ozone. − Disinfection pretreatment strategies upstream of these membranes are therefore limited to the use of chloramines, weaker disinfectants that reduce the effectiveness of downstream ultraviolet treatment processes and are associated with the formation of highly toxic disinfection byproducts, including N -nitrosodimethylamine. , Alternatively, chlorine is sometimes used upstream of membrane systems, but a costly dechlorination step must be implemented prior to reverse osmosis (RO) to protect the membranes. The development of membrane materials that withstand exposure to strong oxidants is therefore a well-acknowledged need in the field of membrane separations.…”

Section: Introductionmentioning

confidence: 99%

Impact of Oxidative Chemicals on Hydrophobic Porous Membranes Used in Membrane Distillation

Cairney,

Hjelvik,

Straub

2024

ACS Appl. Eng. Mater.

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Direct treatment of water purification membranes with strong oxidative chemicals, such as ozone and chlorine, is a promising avenue to prevent fouling and improve the water treatment performance. In this work, we investigate the oxidation resistance of hydrophobic polymers commonly used in membrane distillation by probing the impact of ozone and chlorine exposure on the membrane structure, chemistry, and desalination performance. To probe oxidative behavior, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polypropylene (PP) membranes were exposed to sodium hypochlorite (10,000 ppm, pH 4) and ozone (15 ppm, pH 7) solutions for up to 72 and 3 h, respectively. We then characterized the membrane samples using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle measurements, and desalination performance testing. Our results indicate that PTFE membranes show no chemical, structural, or desalination performance changes after exposure to the highest doses of chlorine and ozone, with only minor decreases in the water contact angle (less than 15%) after exposure to oxidants. PVDF also showed no observable changes in structure or performance, although XPS analysis indicated possible defluorination of the surface after oxidant exposure. PP membranes showed the most severe degradation, with surface cracking, chemical changes, and complete failure in desalination testing after exposure to 10,000 ppm chlorine for 1 h or 15 ppm ozone for 30 min. Measurements of salt rejection and water flux of the pristine and oxidized membranes showed greater than 99.9% rejection and minimal changes in water flux regardless of oxidant or exposure length, except in the case of PP which showed failure during testing. Our results provide insights into the degradation behavior of hydrophobic polymer membranes and demonstrate the promise of using PTFE and PVDF membranes combined with strong oxidants in water treatment.

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“…Water reuse and desalination are essential to relieve global water scarcity by purifying water from sustainable, nontraditional sources. , Reverse osmosis (RO) is a widely used process in desalination and water reuse treatment trains because it offers energy efficiency, scalability, and reliable removal of key contaminants (e.g., dissolved ions and organic carbon). − However, current RO membrane materials suffer from critical shortcomings. Notably, RO membrane materials readily degrade when exposed to free chlorine commonly used in water treatment trains. , As a result, RO membranes cannot be easily cleaned, and costly dechlorination steps must often be employed .…”

Section: Introductionmentioning

confidence: 99%

Water Desalination via Pressure-Driven Distillation with Chlorine-Resistant and Large-Area Polymeric Membranes

Nguyen

Lopez

Lee

et al. 2023

Environ. Sci. Technol. Lett.

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Pressure-driven distillation is a separation process in which hydraulic pressure is used to drive water vapor transport across an air-trapping porous hydrophobic membrane. Current development of pressure-driven distillation is limited by a lack of robust, large-area membranes. Here, we report desalination using pressure-driven vapor transport through scalable polymeric polytetrafluorethylene membranes. The membranes showed pressure-driven water flow with near-complete rejection of sodium chloride (greater than 99%) under hydraulic pressures of up to 10.3 bar. Membrane structure, surface chemistry, and desalination performance were found to be unaffected by doses of sodium hypochlorite up to 3000 ppm h. Flux decline due to biofouling from Pseudomonas aeruginosa bacterium was effectively mitigated using chlorine. Membranes also exhibited high temperature resilience with operation up to 60 °C. Overall, this work demonstrates the use of large-area polymeric materials in pressure-driven distillation and highlights key advantages in chlorine and heat tolerance.

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Unlocking the potential of polymeric desalination membranes by understanding molecular-level interactions and transport mechanisms

Abstract: Polyamide reverse osmosis (PA-RO) membranes achieve remarkably high water permeability and salt rejection, making them a key technology for addressing water shortages through processes including seawater desalination and wastewater reuse....

Cited by 16 publications

References 146 publications

Real-time structural dynamics of the ultrafast solvation process around photo-excited aqueous halides

Real-time structural dynamics of the ultrafast solvation process around photo-excited aqueous halides

Impact of Oxidative Chemicals on Hydrophobic Porous Membranes Used in Membrane Distillation

Water Desalination via Pressure-Driven Distillation with Chlorine-Resistant and Large-Area Polymeric Membranes

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