Progress of stimuli responsive membranes in water treatment

Low, Siew Chun; Ng, Qi Hwa

doi:10.1016/b978-0-12-814503-6.00004-5

Cited by 10 publications

(6 citation statements)

References 118 publications

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“…Comparing these two methods, grafting-to is more convenient to control as, in this case, the pre-synthesized reactive groups can be purified before grafting, whereas grafting-from provides an edge when it comes to controlling the thickness of the grafted layer, as in this case the modifiers can be added over time. Further, in the grafting-from method, various processes are available to activate the surface of the polymeric membrane for grafting polymerization, which includes plasma treatment, UV irradiation, ozone treatment, and gamma-ray irradiation [ 65 ]. Many recent studies have shown that surface grafting can be used to modify a hydrophilic membrane surface into a hydrophobic surface, making them suitable for MD operations.…”

Section: Fundamentals Of MD Membranementioning

confidence: 99%

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

et al. 2020

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Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, and wetting are some serious challenges faced in MD operations. Thus, in recent years, various studies have been carried out on the modification of these MD membranes by incorporating nanomaterials to overcome these challenges and significantly improve the performance of these membranes. This review provides a comprehensive evaluation of the incorporation of new generation nanomaterials such as quantum dots, metalloids and metal oxide-based nanoparticles, metal organic frameworks (MOFs), and carbon-based nanomaterials in the MD membrane. The desired characteristics of the membrane for MD operations, such as a higher liquid entry pressure (LEPw), permeability, porosity, hydrophobicity, chemical stability, thermal conductivity, and mechanical strength, have been thoroughly discussed. Additionally, methodologies adopted for the incorporation of nanomaterials in these membranes, including surface grafting, plasma polymerization, interfacial polymerization, dip coating, and the efficacy of these modified membranes in various MD operations along with their applications are addressed. Further, the current challenges in modifying MD membranes using nanomaterials along with prominent future aspects have been systematically elaborated.

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Section: Fundamentals Of MD Membranementioning

confidence: 99%

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

et al. 2020

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“…Thus, the tunability of the membrane flux rate as well as salt rejection still remains a significant challenge and considerable efforts are underway both academically and industrially [7]. Various physical and chemical techniques have been proposed to modify the membrane surface to switch the flux rate and salt rejection to enhance membrane performance [8]. For this purpose, the control of the membrane structure is needed, which may not always be feasible.…”

Section: Introductionmentioning

confidence: 99%

Surface Modification of TFC-PA RO Membrane by Grafting Hydrophilic pH Switchable Poly(Acrylic Acid) Brushes

Abbas

Mushtaq

Cheema

et al. 2020

Advances in Polymer Technology

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The grafting of pH-responsive poly(acrylic acid) (PAA) brushes was carried out on the surface of a commercial TFC-PA membrane using surface-initiated atom transfer radical polymerization (SI-ATRP). Poly(t-butyl acrylate) was polymerized through the SI-ATRP method followed by its acid hydrolysis to form PAA hydrophilic polymer brushes. Surface morphology, permeation flux, salt rejection, and pore sizes were investigated. The contact angle for water was reduced from 50° for a pristine membrane to 27° for the modified membrane due to a modification with the hydrophilic functional group and its brush on membrane surfaces. The flux rate also increased noticeably at lower pH values relative to higher pH for the modified membranes, while the flux remains stable in the case of pristine TFC-PA membranes. There is slight transition in the water flux rate that was also observed when going from pH values of 3 to 5. This was attributed to the pH-responsive conformational changes for the grafted PAA brushes. At these pH values, ionization of the COOH group takes place below and above pKa to influence the effective pore dimension of the modified membranes. At a lower pH value, the PAA brushes seem to permit tight structure conformation resulting in larger pore sizes and hence more flux. On the other hand, at higher pH values, PAA brushes appeared to be in extended conformation to induce smaller pore sizes and result in less flux. Further, pH values were observed to not significantly affect the NaCl salt rejection with values observed in between 98.8% and 95% and close to that of the pristine TFC-PA membranes. These experimental results are significant and have immediate implication for advances in polymer technology to design and modify the “switchable membrane surfaces” with controllable charge distribution and surface wettability, as well as regulation of water flux and salt.

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“…Grafting-from technique is useful in managing the thickness of the grafting layer as the monomer concentration can be increased over time. However, it is arduous to manage the final chain length of the responsive material using this approach [49]. Surface initiation sites required for graft polymerization can be produced by using a chemical initiator, UV/gamma irradiation, or plasma [50].…”

Section: Classification Of Chemical Graftingmentioning

confidence: 99%

Surface Design of Liquid Separation Membrane through Graft Polymerization: A State of the Art Review

et al. 2021

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Surface modification of membranes is an effective approach for imparting unique characteristics and additional functionalities to the membranes. Chemical grafting is a commonly used membrane modification technique due to its versatility in tailoring and optimizing the membrane surface with desired functionalities. Various types of polymers can be precisely grafted onto the membrane surface and the operating conditions of grafting can be tailored to further fine-tune the membrane surface properties. This review focuses on the recent strategies in improving the surface design of liquid separation membranes through grafting-from technique, also known as graft polymerization, to improve membrane performance in wastewater treatment and desalination applications. An overview on membrane technology processes such as pressure-driven and osmotically driven membrane processes are first briefly presented. Grafting-from surface chemical modification approaches including chemical initiated, plasma initiated and UV initiated approaches are discussed in terms of their features, advantages and limitations. The innovations in membrane surface modification techniques based on grafting-from techniques are comprehensively reviewed followed by some highlights on the current challenges in this field. It is concluded that grafting-from is a versatile and effective technique to introduce various functional groups to enhance the surface properties and separation performances of liquid separation membranes.

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Progress of stimuli responsive membranes in water treatment

Cited by 10 publications

References 118 publications

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

Surface Modification of TFC-PA RO Membrane by Grafting Hydrophilic pH Switchable Poly(Acrylic Acid) Brushes

Surface Design of Liquid Separation Membrane through Graft Polymerization: A State of the Art Review

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