Sulfonated Graphene Oxide Nanosheets Research Articles

Janus sulfonated graphene oxide nanosheets with excellent interfacial properties for enhanced oil recovery

In this article, we prepared Janus sulfonated graphene oxide nanosheets (JSGO) by a facile method for large-scale production. Unlike previous single-sided modifications of graphene oxide (GO), the smart JSGO nanofluid that can automatically find oil was obtained by modifying the double sides of GO. Benefiting from the introduction of sulfonic acid groups, JSGO had outstanding dispersity and stability under extreme conditions. Furthermore, JSGO exhibited excellent interfacial properties due to its amphiphilic characteristic. On the one hand, JSGO can reduce interfacial tension by 71% and form a strong interfacial film at the oil–water contact, achieving piston displacement with high sweep efficiency. On the other hand, JSGO had a strong ability in wettability reversal that can turn the hydrophobic surface into completely hydrophilic. These excellent properties of JSGO nanofluid contributed to obtaining an additional 18.4% recovery factor at low concentration (100 mg/L) and low injection volume (0.3 pore volume). As a result of the simple preparation, high performance, and excellent dispersion stability of JSGO nanofluid, it can be utilized as a chemical agent to enhance oil recovery in the harsh environment of reservoirs.

A facile strategy to construct layered membranes with high and stable proton conductivity based on sulfonated graphene oxide

Spin coating as an easy-operation strategy to construct layered membranes has been widely mentioned in the fields of microelectronics, energy storage, and conversion, etc. In this research, the successful construction of proton exchange membranes (PEMs) bearing layered structure consisting of sulfonated graphene oxide (SGO) nanosheets and polyvinyl chloride (PVC) with the spin coating method has been demonstrated by the identification of the multilayered dispersion of components and compact structure. The hydrophilic SGO nanosheets could increase the hydrophilicity of composite membranes since they bore a large number of polar oxygen functional groups. Phosphoric acid (PA) can be combined through the formed intermolecular hydrogen bonds between PA molecules and SGO nanosheets. The content of PA in PEMs can be adjusted by controlling the concentration of PA solutions, immersion temperature, and duration time. A comparative study with the membrane from the solution casting method has been performed, expecting to understand the influence of layered structure on membrane performance. It was found that the well-ordered distribution of SGO nanosheets facilitated proton conduction, demonstrating from the proton conductivity of 3.63 × 10−2 S/cm at 150°C. The fine proton conductivity stability, for instance, the result of 2.71 × 10−2 S/cm at 140°C lasting 1000-hour supported the component stability and mechanical strength. The research revealed that the spin coating technique could provide a facile and effective strategy to construct well-ordered membrane electrolytes for the application of high- temperature proton exchange membrane fuel cells.

Highly selective custom‐made chitosan based membranes with reduced fuel permeability for direct methanol fuel cells

AbstractCustom‐made nanocomposite proton exchange membranes (PEMs) are fabricated using the blends of sulfonated chitosan (S‐Chitosan) and sulfonated graphene oxide (SGO) nanosheets for direct methanol fuel cells (DMFCs). Sulfonation of chitosan and GO are carried out by 1,3‐propane sultone and sulfanilic acid, respectively. Scanning electron microscope (SEM) with energy dispersive X‐ray investigation revealed that the thick, folded and wrinkled sheet‐like morphology of SGO and the existence of elemental sulfur. SEM and atomic force microscopy images showed the uniform dispersion of hydrophilic SGO nanosheets. Besides the S‐Chitosan/SGO membranes showed higher water uptake, swelling ratio and ion exchange capacity due to the enhancement in hydrophilicity. The modified PEMs displayed improvement in proton conductivity since the ion‐exchangeable sulfonic acid groups facilitate the proton conduction and effectively resist the methanol permeability by forming a strong hydrogen bond network with chitosan and thus diminish the void volume. Particularly, S‐Chiotsan‐1 membrane showed superior proton conductivity of 4.86 × 10−3 Scm−1 at (25°C), selectivity of 1.89 × 105 Scm−3 s and lesser methanol permeability of 2.57 × 10−8 cm2s−1. Overall results suggest that the S‐Chitosan/SGO membranes found to be a suitable alternate for Nafion® in DMFCs.

Investigating the efficacy of PVDF membranes customized with sulfonated graphene oxide nanosheets for enhanced permeability and antifouling

Poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membranes are fabricated using the incorporation of sulfonated graphene oxide (SGO) nanosheets with the aim of enhanced separation of biomacromolecular protein and natural organic matter. The effect of the addition of SGO on the PVDF membrane is evaluated with specific emphasis on morphology, surface hydrophilicity, pure water flux (PWF), bovine serum albumin (BSA) and humic acid (HA) separation. The experimental results revealed that the PVDF membrane with 2 wt.% SGO exhibited the enhanced PWF of 155.5 Lm-2 h-1 and more than 98% of BSA and HA rejection due to its improved hydrophilicity and more porous morphology. The antifouling ability of the PVDF membranes is improved to a great extent with the incorporation of SGO nanosheets is confirmed by the greater than 95% of flux recovery ratio during the filtration of BSA and HA. SGO inherits useful functional groups from graphene oxide and possesses better miscibility with the incorporated polymer matrix due to the presence of strongly charged -SO3- units which is attributed to the relatively enhanced hydrophilicity of the modified membranes. Especially, SGO has extensively employed in membrane-based water treatment as SGO promotes better water permeability performances, together with adequate resistance towards hydraulic pressure. In view of these entire outcomes, it is apparent that the SGO incorporated PVDF nanocomposite UF membrane proves the potential for water and wastewater treatment applications.

Layer-by-layer assembled GO-based membranes with high long-standing stability and chemical resistance applied in dye separation and desalination

The Graphene oxide (GO) membranes, as the most studied and accessible two-dimensional (2D) membranes, have performed their expected separation performance, but instability of these delicate membranes still hinders their development. Layer-by-layer (LBL) self-assembly is one smart method for preparing versatile 2D membranes with stable structure by chemical bonds or other forces. Herein, the 2D GO laminar membranes were prepared on the modified Nylon-6 substrates via LBL method by employing positively charged P–GO (guanidine modified GO nanosheets) and negatively charged S–GO (sulfonated GO nanosheets) as assembly flakes. This smart strategy was established on the superiority of LBL method by adjusting the assembly layer number and outermost charge when faced up with the different targeted contaminants. Benefited from the compact structures and intense charge, the LBL membranes can almost remove all the employed dyes (above 98% rejection for ML11 membrane). Furthermore, these membranes also show the high selectivity to water molecular in desalination (93.4% rejection to Na2SO4 and 72.7% rejection to NaCl for ML11 membrane). The membranes can endure the filtration of dye wasterwater and salt solution for above 168 h under cross-flow mode without rejection decline. Also, these versatile LBL membranes reveal high resistance to both chemical corrosion and bacterial attack, which is suitable for the continuous separation even under hostile external environment.

SPVdF-HFP/SGO nanohybrid proton exchange membrane for the applications of direct methanol fuel cells

Sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVdF-HFP)/sulfonated graphene oxide (SGO) hybrid membrane was prepared via solution casting process. Incorporation of SGO nanosheets into SPVdF-HFP matrix increases the density of sulfonic acid moieties of hybrid membrane. This offer better water uptake, good proton conductivity, than pristine SPVdF-HFP membrane. Additionally, the complex structure generated between SGO and membrane chains helps to reduce methanol uptake and swelling ratio of the hybrid membrane. The formation of electrostatic interaction between membrane backbone and SGO skeleton helps the SPVdF-HFP/SGO to retained lower weight loss than SPVdF-HFP during TGA analysis. The presence of SGO nanosheets in membrane matrix is confirmed by morphological studies. The SPVdF-HFP/SGO membrane achieved maximum proton conductivity of 7.8 mS/cm at 70 °C and low methanol permeability of 2.567 × 10−7 cm2/s at 70 °C whereas the pristine SPVdF-HFP membrane exhibits 1.7 mS/cm and 3.105 × 10−7 cm2/s. From the obtained good results of hybrid membrane, we believe that the SPVdF-HFP/SGO would be a promising candidate for the application of DMFCs.

Sulfonated graphene oxide incorporated thin film nanocomposite nanofiltration membrane to enhance permeation and antifouling properties

Thin film nanocomposite (TFN) membranes embedded with sulfonated graphene oxide (SGO) were fabricated to improve the hydrophilicity, salt rejection and antifouling of nanofiltration (NF) membrane. In this study, the surface properties and structure of polyamide (PA) layer were improved by incorporating SGO into the PA layer. It was prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on the polysulfone substrate surface. The PA layer thickness of TFN membranes decreased and the hydrophilicity and zeta potential of them were improved after incorporating the SGO. According to NF filtration tests, TFN membrane including 0.3 wt% of SGO (TFN 0.3) gave the highest water flux, which was 87.3% higher than that of TFC membrane. Interestingly, despite the significant increase in water permeability, the salt rejection of both membranes was similar due to the improved cross-linking and low molecular weight cut-off (MWCO) of the TFN 0.3 membrane. Furthermore, it showed high antifouling property in long-term NF test, compared to the pristine TFC membrane. The current study may lead to a facile strategy by using SGO nanosheets to improve the hydrophilicity and antifouling properties of NF membrane.

Graphene Oxide Membranes with Conical Nanochannels for Ultrafast Water Transport.

Membrane-based separations have been increasingly utilized to address global energy crisis and water scarcity. However, the separation efficiency often suffers from the trade-off between membrane permeability and selectivity. Although great efforts have been devoted, a membrane with both high permeability and high selectivity remains a distant prospect. Inspired by the hourglass structure and ultrafast water transport in aquaporins, we propose a novel approach to fabricating membranes with conical nanochannels to reduce the mass transfer resistance and to introduce Laplace pressure as the internal driving force, which successfully breaks the permeability/selectivity trade-off. First, sulfonated polyaniline (SPANI) nanorods were in situ-synthesized and vertically aligned on sulfonated graphene oxide (SGO) nanosheets, forming SGO-SPANI X composites. Then, the graphene oxide (GO) membranes were fabricated by assembling SGO-SPANI X composites through pressure-assisted filtration, in which the SPANI nanorods would bend and flatten on the SGO nanosheets under low shear force, forming stripe arrays on SGO nanosheets. The tilted stripe arrays between the adjacent SGO nanosheets form the conical nanochannels inside GO membranes. The conical nanochannels significantly decreased the steric hindrance and enabled the generation of Laplace pressure as the internal driving force within membranes. Consequently, the resulting membranes exhibit an ultrahigh water permeability of 1222.77 L·m-2·h-1·bar-1 and high efficiency in dye removal from water with a rejection of 90.44% and permeability of 528 L·m-2·h-1·bar-1.

Enhancement in Performance of Sulfonated PES Cation-Exchange Membrane by Introducing Pristine and Sulfonated Graphene Oxide Nanosheets Synthesized through Hummers and Staudenmaier Methods

ABSTRACTSulfonated polyether sulfone-based cation-exchange membranes are prepared by incorporating different amounts of graphene oxide and sulfonated graphene oxide nanosheets. The graphene oxide nanosheets are synthesized according to Staudenmaier and Hummer methods and functionalized using 3-mercaptopropyl trimethoxysilane. Transport properties of nanocomposite membranes including ion-exchange capacity, transport number, and conductivity as well as their thermal stabilities are enhanced by incorporating sulfonated graphene oxide rather than graphene oxide. Also, the enhancement is more significant for the nanocomposites having functionalized graphene oxide synthesized by Staudenmaier method than those by Hummers method due to higher density of active sites in the Staudenmier graphene oxides for functionalization.

Preparation and physicochemical performance study of proton exchange membranes based on phenyl sulfonated graphene oxide nanosheets decorated with iron titanate nanoparticles

Usage of phenyl sulfonated graphene oxide (SGO) as a support material for the dispersion of iron titanate (Fe2TiO5) nanoparticles presents new methods to develop advanced composite materials for proton exchange membranes. Fe2TiO5 nanoparticles were deposited onto graphene oxide (GO) nanosheets by means of one-step solvothermal method. The novel SGO/Fe2TiO5 hybrid material dispersed in poly(vinyl alcohol) (PVA) matrix in order to fabricate thin film membranes by solution casting method. Proton conductivity and methanol permeability of nanocomposite membranes were tested to expose their potential for direct methanol fuel cell (DMFC) application. The results showed that the nanocomposite membrane containing SGO/Fe2TiO5 (5 wt %) can yield a high proton conductivity (σ = 0.061 S cm−1), low methanol permeability (P = 4.78 × 10−6 cm2 s−1) and good power density (PD = 20.47 mW cm−2) at 30 °C. The membrane's performance evaluated from the ion exchange capacity, water uptake, methanol permeability, proton conductivity and mechanical and thermal properties demonstrated the role of Fe2TiO5/SGO nanosheets as an effective hybrid material in the development of proton exchange membranes.

Cationic and anionic azo-dye removal from water by sulfonated graphene oxide nanosheets in Nafion membranes

The use of graphene oxide flakes functionalized with 3-amino-1-propanesulfonic acid (GOSULF), as a powder or incorporated into a Nafion membrane, for the removal of cationic and anionic dyes is studied.