Understanding the pH-responsive behavior of graphene oxide membrane in removing ions and organic micropollulants

Oh, Yonghui; Armstrong, Dana L.; Finnerty, Casey; Zheng, Sunxiang; Hu, Meng; Torrents, Alba; Mi, Baoxia

doi:10.1016/j.memsci.2017.07.005

Cited by 93 publications

(58 citation statements)

References 53 publications

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“…The membrane showed fast response as a function of pH for its potential applications; the fluxes at pH 8 are around 375 l/(m 2 h), while, with changing the feed to pH 3 buffer, the fluxes across the membrane decreased quickly to around 123 l/(m 2 h) within the first recording period, about 40 s. Therefore, the pH-responsive coefficient was about 0.328, indicating a good response of the membrane at the mentioned pHs. This value is mainly a fraction, which contradicts to others found in literature, as other membranes showed a reversed behavior at the same tested pHs [67].…”

Section: Langmuir and Freundlich Isothermscontrasting

confidence: 99%

“…All the Ce 4+ ,Pr 3+ ,Sm 3+ ,Gd 3+ ,Dy 3+ , and Ho 3+ solutions are used as feed solution only within 48 h after preparation. In the filtration test, membranes are conditioned with buffers of pH 3 and pH 8 firstly[67,68].Then the permeability of Ce 4+ ,Pr 3+ ,Sm 3+ ,Gd 3+ ,Dy 3+ , and Ho 3+ solutions is monitored until the stabilization of membrane is reached and the filtrate is collected. Concentrations of Ce 4+ ,Pr 3+ , Sm 3+ ,G d 3+ ,D y 3+ , and Ho 3+ ions in the filtrate solution are measured with Buck Scientific 210 VGP Atomic Absorption Spectrophotometer.…”

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confidence: 99%

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Recent Drifts in pH-Sensitive Reverse Osmosis

Ibrahim¹,

El-Gammal²

2018

Wastewater and Water Quality

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Preparation of some smart PAm-ZTS pH-responsive membranes, via reactions between ZTS and PAm under different conditions, was conducted for testing pressure-driven reverse osmosis membranes (PDROMs) in active rejection of Ce 4+ ,Pr 3+ ,Sm 3+ ,Gd 3+ ,Dy 3+ , and Ho 3+ ionic lanthanide species in their 3 + and 4 + states. Recent theoretical models to designate the membrane operations were mathematically itemized, after selective characterization of the PDROMs. The pH scale response of the membrane was confirmed using static adsorption and hydraulic pervasion result estimations. The flux across the PAm-ZTS membrane decreased with the lowering pH value, with drastic decreases between pH 4 and 7, and was both reversible and durable with pH shifts between~3 and~8. At lower pH 3, the individual pores were in a closed-state due to the prolonged structure of the amide chains on the porous surfaces. In contrast, at pH 8, the higher pH value, the membrane pores were in an open-state format, because of the collapsed structures of the amide chains. This grants a clear possible approach for manufacturing some pHresponsive composite membranes and inspires further design for their stimuli-responsive actions by incorporating molecularly designed macromolecules, synthesized by controlled polymerization.

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Section: Langmuir and Freundlich Isothermscontrasting

confidence: 99%

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confidence: 99%

Recent Drifts in pH-Sensitive Reverse Osmosis

Ibrahim¹,

El-Gammal²

2018

Wastewater and Water Quality

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“…Thus, the high drug‐release efficiency at low pH cannot be attributed to the collapse of the frameworks of the FA‐NMOFs. Instead, the high drug‐release efficiency at low pH values should derive from the enhanced positive charge of the material, with the weaker electrostatic interaction with the positively charged 5‐FU leading to a much faster release rate in acidic surroundings (pH 5.5) . In addition, there was no significant change in the PXRD patterns of FA‐MOF‐808 and FA‐NH 2 ‐UiO‐66 after three release cycles in PBS at pH 5.5 (see Figures S18 and S19).…”

Section: Resultsmentioning

confidence: 99%

Folic Acid Functionalized Zirconium‐Based Metal–Organic Frameworks as Drug Carriers for Active Tumor‐Targeted Drug Delivery

Dong

Yang

Zhang

et al. 2018

Chemistry A European J

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Nanoscale metal-organic frameworks (NMOFs) have proven to be a class of promising drug carriers as a result of their high porosity, crystalline nature with definite structure information, and potential for further functionality. However, MOF-based drug carriers with active tumor-targeting function have not been extensively researched until now. Here we show a strategy for constructing active tumor-targeted NMOF drug carriers by anchoring functional folic acid (FA) molecules onto the metal clusters of NMOFs. Two zirconium-based MOFs, MOF-808 and NH -UiO-66, were chosen as models to reduce to the nanoscale for application as drug carriers, and then the terminal carboxylates of FA molecules were coordinated to Zr clusters on the surfaces of the nanoparticles by substitution of the original formate or terminal -OH ligands. The successful modification with FA was confirmed by solid-state C MAS NMR and UV/Vis spectroscopy and other characterization methods. Drug loading and controlled release behavior at different pH were determined by utilizing the anticancer drug 5-fluorouracil (5-FU) as the model drug. Confocal laser scanning microscopy measurements further demonstrated that 5-FU-loaded FA-NMOFs have excellent targeting ability through the efficient cellular uptake of FA-NMOFs. This work opens up a new avenue to the construction of active tumor-targeted NMOF-based drug carriers with potential for cancer therapies.

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“…The protruding oxygen‐containing functional groups keep apart the adjacent GO nanosheets to form nanocapillaries suitable for separation at the NF level . It has been reported that the GO membrane can reject dye molecules, humic acids, micro‐organic pollutants, heavy metal ions such as Pb 2+ /Ni 2+ /Zn 2+ , and also be used for desalination …”

Section: Introductionmentioning

confidence: 99%

“…11 The protruding oxygen-containing functional groups keep apart the adjacent GO nanosheets to form nanocapillaries suitable for separation at the NF level. 7,11 It has been reported that the GO membrane can reject dye molecules, [12][13][14] humic acids, 15,16 micro-organic pollutants, 17 heavy metal ions 14,18,19 such as Pb 2+ /Ni 2+ /Zn 2+ , and also be used for desalination. 20,21 Manipulating the separation performance of the GO membranes has presented a challenge and aroused the interest of the researchers.…”

Section: Introductionmentioning

confidence: 99%

Factors affecting the separation performance of graphene oxide membranes: mechanical support, properties of graphene oxide, and exotic species

Zhao

Yuan

et al. 2017

J of Chemical Tech & Biotech

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BACKGROUND Graphene oxide (GO) membrane with 2‐dimensional nanocapillaries has gained worldwide attention. To manipulate the membrane separation performance, most existing studies focused on sandwiching appropriate species between GO layers. This study aimed to provide multiple strategies to manipulate the GO membrane separation performance, including the mechanical support, properties of GO nanosheets, and exotic species (i.e. cross‐linkers and residual water molecules). RESULTS Used as the support material, compared with the nitrocellulose membrane, the polyvinylidene fluoride membrane offered stronger mechanical strength to ensure a stable flux. Additional mechanical support could be provided by the non‐woven cloth underneath the GO membrane. The use of GO nanosheets with smaller sizes obtained by centrifugation of the GO suspension increased the water flux and NaCl rejection. Cross‐linking GO layers by Ca2+ resulted in a decreased water flux but increased salt rejection. The same phenomena was observed for the GO membranes post‐treated by vacuum drying, which, compared with air drying, evaporated more residual water molecules from the nanocapillaries. CONCLUSION Results suggested that the mechanical support, properties of GO nanosheets, cross‐linkers, and residual water molecules greatly affected the membrane water flux and rejections, which could be utilized as strategies to manipulate the GO membrane separation performance. © 2017 Society of Chemical Industry

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Understanding the pH-responsive behavior of graphene oxide membrane in removing ions and organic micropollulants

Cited by 93 publications

References 53 publications

Recent Drifts in pH-Sensitive Reverse Osmosis

Recent Drifts in pH-Sensitive Reverse Osmosis

Folic Acid Functionalized Zirconium‐Based Metal–Organic Frameworks as Drug Carriers for Active Tumor‐Targeted Drug Delivery

Factors affecting the separation performance of graphene oxide membranes: mechanical support, properties of graphene oxide, and exotic species

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