Efficient removal of sparfloxacin antibiotic from water using sulfonated graphene oxide: Kinetics, thermodynamics, and environmental implications.

Pharmaceutical contamination poses a significant threat to global health. Due to their high solubility in water, antibiotics are difficult to remove. This study produced and used sulfonated graphene oxide (SGO) to adsorb sparfloxacin from aquatic environments. UV-Visible, Fourier transform infrared (FTIR), X-ray diffraction (XRD), XPS, SEM, TEM, EDX, particle size, Thermogravimetric analysis (TGA), and acid-base titration were used to characterize synthesized SGO particles. The BET technique determined SGO's surface area (32.25 m2/g). The calculated pHPZC of SGO was 2.5. Sparfloxacin adsorption onto SGO was analyzed using adsorption duration, medium pH, adsorbent dosages, antibiotic concentration, cations, and solution temperature. The pseudo-second-order kinetic model better described experimental kinetic data than the pseudo-first-order and Elovich models. Equilibrium isotherm data supported the Langmuir model, revealing a peak absorption capacity of 1428.57 µmol/g at 25 °C. The kinetic and isotherm models' applicability was assessed using error analysis. A thermodynamic analysis revealed an endothermic, spontaneous adsorption process with a change in entropy (ΔS) of 114.15 J/mol K and enthalpy (ΔH) of 8.44 kJ/mol. A regeneration analysis showed that SGO adsorption efficiency topped 86.4 % after five cycles.

Sulfonated graphene oxide-based pervaporation membranes inspired by a tortuous brick and mortar structure for enhanced resilience against silica scaling and organic fouling.

A novel tortuous brick-and-mortar structure utilizing intercalation of polyvinyl alcohol (PVA) on sulfonated graphene oxide (SGO) membranes was specifically tailored for brine treatment by pervaporation to ensure excessive resistance to silica scaling and organic fouling, as well as ultrafast water transport without compromising salt rejection. The synthesized SGO membrane showed a smoother surface morphology, improved zeta potential, and a higher hydration capacity than the graphene oxide (GO) membrane. Further intercalation of PVA through glutaraldehyde (GA) crosslinking, confirmed by Fourier transform infrared spectroscopy and X-ray diffraction analysis, conferred increased cohesiveness, and the SGO-PVA-GA membrane was therefore able to withstand ultrasonication tests without any erosion of the coating layer. According to a pervaporative desalination test, the SGO-PVA-GA membrane exhibited 62 kg m-2 h-1 of permeate flux, with an extraordinary salt rejection of 99.99% for a 10 wt% NaCl feed solution at 65 °C. The 72 h organic fouling, silica scaling, and combined fouling and scaling tests proved that the SGO-PVA-GA membrane sustains a stable flux with less scaling and fouling than the GO-PVA-GA membrane, attributable to dense surface negative charges and great hydration capacities caused by sulfonic acid. Thus, the SGO-PVA-GA membrane offers superlative advantages for long-term brine treatment by pervaporation, related to its ability to withstand silica scaling and organic fouling.

Sulfonated GO coated carbon electrodes with cation-selective functions for enhanced capacitive deionization of saltwater.

Deionization of salt, contaminated underground and inorganic waste waters for water recycling and reuse is of increasing importance mainly due to the shortage of freshwater worldwide. Membrane capacitive deionization (MCDI) possessing a high electrosorption capacity and energy efficiency has been considered a promising method for desalination. However, the MCDI reaction system has limited applications because of the high interfacial resistance during operation. In the present work, the novel sulfonated graphene oxide (SGO) serving as a hydrophilic cation exchange membrane that was coated directly on the activated carbon (AC) electrode was prepared to enhance capacitive deionization of saltwater. Experimentally, the electrosorption capacity and charge efficiency of the AC/SGO (negative)||AC (positive) electrode pair using the coated SGO thin film increased from 12.8 to 19.8 mg/g and 56.7 to 89.3%, respectively. The enhancements were associated with the reduction of the co-ion effect during electrosorption. The strong negative PhSO3- group grafted on the SGO thin film could selectively accelerate the transport rate of cations during CDI. The increase of the charge efficiency also led to lower implemented current. This work demonstrates a simple, low-cost and effective desalination method that will likely have many new applications especially in water recycling and reuse.

Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum.

The current study was designed to assess nanomaterial sulfonated graphene oxide (SGO) potential in improving tolerance of wheat chloroplasts against nitrate (NS) and ammonium (AS) toxicity. Triticum aestivum cv. Ekiz was grown under SGOs (50-250-500 mg L-1) with/without 140 mM NS and 5 mM AS stress. SGOs were eliminated the adverse effects produced by stress on chlorophyll fluorescence, potential photochemical efficiency and physiological state of the photosynthetic apparatus. SGO reversed the negative effects on these parameters. Upon SGOs exposure, the induced expression levels of photosystems-related reaction center proteins were observed. SGOs reverted radical accumulation triggered by NS by enabling the increased superoxide dismutase (SOD) activity and ascorbate (AsA) regeneration. Under AS, the turnover of both AsA and glutathione (GSH) was maintained by 50-250 mg L-1 SGO by increasing the enzymes and non-enzymes related to AsA-GSH cycle. 500 mg L-1 SGO prevented the radical over-accumulation produced by AS via the regeneration of AsA and peroxidase (POX) activity rather than GSH regeneration. 50-250 mg L-1 SGO protected from the NS+AS-induced disruptions through the defense pathways connected with AsA-GSH cycle represented the high rates of AsA/DHA and, GSH/GSSG and GSH redox state. Our findings specified that SGO to NS and AS-stressed wheat provides a new potential tool to advance the tolerance mechanism.

Fabrication and Characterization of Sulfonated Graphene Oxide (SGO) Doped PVDF Nanocomposite Membranes with Improved Anti-Biofouling Performance.

Emergence of membrane technology for effective performance is qualified due to its low energy consumption, no use of chemicals, high removal capacity and easy accessibility of membrane material. The hydrophobic nature of polymeric membranes limits their applications due to biofouling (assemblage of microorganisms on surface of membrane). Polymeric nanocomposite membranes emerge to alleviate this issue. The current research work was concerned with the fabrication of sulfonated graphene oxide doped polyvinylidene fluoride (PVDF) membrane and investigation of its anti-biofouling and anti-bacterial behavior. The membrane was fabricated through phase inversion method, and its structure and morphology were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-rays diffraction (XRD) and thermo gravimetric analysis (TGA) techniques. Performance of the membrane was evaluated via pure water flux; anti-biofouling behavior was determined through Bovine Serum albumin (BSA) rejection. Our results revealed that the highest water flux was shown by M7 membrane about 308.7 Lm-2h-1/bar having (0.5%) concentration of SGO with improved BSA rejection. Furthermore, these fabricated membranes showed high antibacterial activity, more hydrophilicity and mechanical strength as compared to pristine PVDF membranes. It was concluded that SGO addition within PVDF polymer matrix enhanced the properties and performance of membranes. Therefore, SGO was found to be a promising material for the fabrication of nanocomposite membranes.

Fabrication and Characterization of Sulfonated Graphene Oxide-Doped Polymeric Membranes with Improved Anti-Biofouling Behavior.

In this study, cellulose acetate (CA) was blended with sulfonated graphene oxide (SGO) nanomaterials to endow a nanocomposite membrane for wastewater treatment with improved hydrophilicity and anti-biofouling behavior. The phase inversion method was employed for membrane fabrication using tetrahydrofuran (THF) as the solvent. The characteristics of CA-SGO-doped membranes were investigated through thermal analysis, contact angle, SEM, FTIR, and anti-biofouling property. Results indicated that anti-biofouling property and hydrophilicity of CA-SGO nanocomposite membranes were enhanced with addition of hydrophilic SGO nanomaterials in comparison to pristine CA membrane. FTIR analysis confirmed the successful decoration of SGO groups on CA membrane surface while revealing its morphological properties through SEM analysis. Thermal analysis performed using DSC confirmed the increase in thermal stability of CA-SGO membranes with addition of SGO content than pure CA membrane.

Cementitious grain-boundary passivation for flexible perovskite solar cells with superior environmental stability and mechanical robustness.

The power conversion effciency (PCE) of flexible perovskite solar cells (PSCs) has increased rapidly, while the mechanical flexibility and environmental stability are still far from satisfactory. Previous studies show the environmental degradation and ductile cracks of perovskite films usually begin at the grain boundaries (GBs). Herein, sulfonated graphene oxide (s-GO) is employed to construct a cementitious GBs by interacting with the [PbI6]4- at GBs. The resultant s-GO-[PbI6]4- complex can effectively passivate the defects of vacant iodine, and the devices with s-GO exhibit remarkable waterproofness and flexibility due to the tough and water-insoluble GBs. The champion PCE of 20.56% (1.01 cm2) in a device treated with s-GO is achieved. This device retains 90% of its original PCE after 180 d stored in the ambient condition, as well as over 80% retention after 10,000 bending cycles at a curvature radius of 3 mm.

Mechanical Properties and Chemical Durability of Nafion/Sulfonated Graphene Oxide/Cerium Oxide Composite Membranes for Fuel-Cell Applications.

To improve both the mechanical and chemical durability of Nafion membranes for polymer electrolyte membrane fuel-cells (PEMFCs), Nafion composite membranes containing sulfonated graphene oxide (SGO) and cerium oxide (CeO2; ceria) were prepared by solution casting. The structure and chemical composition of SGO were investigated by FT-IR and XPS. The effect of the sulfonation, addition of SGO and ceria on the mechanical properties, proton conductivity, and chemical stability were evaluated. The addition of SGO gave rise to an increase in the number of sulfonic acid groups in Nafion, resulting in a higher tensile strength and proton conductivity compared to that of graphene oxide (GO). Although the addition of ceria was found to decrease the tensile strength and proton conductivity, Nafion/SGO/ceria composite membranes exhibited a higher tensile strength and proton conductivity than recast Nafion. Measurement of the weight loss and SEM observations of the composite membranes after immersing in Fenton's reagent indicate an excellent radical scavenging ability of ceria under radical degradation conditions.

Investigation of heterogeneous sulfonated graphene oxide to hydrolyze cellulose and produce dark fermentative biohydrogen using Enterobacter aerogenes.

The main aim of this work was investigating the potential of sulfonated graphene oxide (sGO) for hydrolysis of cellulosic substrates and dark fermentative hydrogen production from obtained hydrolysates using E. aerogenes. Sulfonation of graphene oxide was performed using chlorosulfonic acid which showed a high acid density of 4.63 mmol/g. Influence of the reaction time (1-5 h), temperature (90-180 °C) and sGO dosage (62.5-500 mg in 25 mL reaction volume) on the hydrolysis of pretreated microcrystalline cellulose was experimented. It revealed that the yield of glucose and total reducing sugars and selectivity can reach 454.4 ± 22.20 mg/g, 682.6 ± 30.67 mg/g and 95.5%, respectively, at 150 °C for 3 h using 250 mg sGO. The maximum hydrogen efficiency of 150.0 ± 5.65 mL/g was achieved under optimized conditions, which was 2.2-fold higher than that from the pretreated MCC substrate as control in the absence of sGO (67.3 ± 8.84 mL/g).

Sulfonated graphene oxide and titanium dioxide coated with nanostructured polyaniline nanocomposites as an efficient cathode catalyst in microbial fuel cells.

In this study, sulfonated graphene oxide (SGO) was synthesized as potential conducting matrix to improve the properties of catalyst for single chamber microbial fuel cells (SC-MFCs). Here, TiO2 and Polyaniline (PAni) nanoparticles were anchored over SGO and the resulting SGO-TiO2-PAni nanocomposites were used as a potential cathode catalyst in MFCs. We have also examined the performance of SGO-TiO2-PAni compared to GO-TiO2-PAni and TiO2-PAni catalyst. The structural and morphological analyses were examined using a variety of characterization techniques. TiO2 nanoparticles bridged PAni and SGO through hydrogen bonding/electrostatic interaction and improved the thermal stability of SGO-TiO2-PAni catalyst. The electrochemical characterizations of these nanocatalysts suggest that the SGO-TiO2-PAni showed higher reduction current value (-0.46 mA), enhanced stability, and lower internal resistance (46.2 Ω) in comparison to GO-TiO2-PAni and TiO2-PAni towards oxygen reduction reactions (ORR). Consequently, MFC using SGO-TiO2-PAni demonstrated a maximum power density of 904.18 mWm-2 than that of GO-TiO2-PAni (734.12 mWm-2), TiO2-PAni (561.5 mWm-2) and Pt/C (483.5 mWm-2). The enhanced catalytic activity of SGO-TiO2-PAni catalyst was ascribed to the high electronic conductivity and long-term permanence of the nanocomposite. These superior electrochemical results suggested that the SGO-TiO2-PAni catalyst could be applied as a potential alternative to the commercial Pt/C cathode catalyst for the application of MFCs.

Novel sulfonated graphene oxide incorporated polysulfone nanocomposite membranes for enhanced-performance in ultrafiltration process.

A novel polysulfone (PSf) nanocomposite ultrafiltration (UF) membrane using sulfonated graphene oxide (SGO) as additives was fabricated and investigated. SGO nanoparticles were chemically synthesized from graphene oxide (GO) by using sulfuric acid (H2SO4) and were confirmed by Raman and Fourier transform infrared (FTIR) spectroscopy. The morphology of prepared membranes was characterized by scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and atomic force microscopy (AFM). Results showed that adding small amount (less than 0.3 wt%) of SGO improved wettability, porosity and mean pore size of PSf/SGO membranes compared to the pristine PSf membrane and significantly enhanced the water flux of SGO incorporated PSf membranes. In UF performance, the nanocomposite membrane prepared by adding 1.5 w/w% SGO of PSf (designated as M1.5) showed the highest water flux result, which was 125% higher than the control PSf membrane (no SGO addition). Interestingly, there was no trade-off between water flux and bovine serum albumin (BSA) rejection, i.e more than 98% BSA rejection. The addition of SGO hydrophilic additives also showed better results in long-term BSA separation performance. The enhancement of hybrid membrane's properties was attributed to the hydrophilicity of sulfonic acid group (SO3H) on the surface of SGO additive. This study suggested that the SGO nanoparticle is a promising candidate to modify the PSf UF membranes.

Sulfonated graphene oxide as an adsorbent for removal of Pb2+ and methylene blue.

One of the major challenges encountered in some conventional nano-structured adsorbents such as graphene oxide (GO) and graphene is the structural limits including serious aggregation and hydrophilic surface in water. And the sulfanilic acid functionalized graphene oxide (SGO) can powerfully attract positively charged pollutants. Therefore, the SGO served as an adsorbent to remove dyes and toxic metal ions from aqueous solution were intensively investigated. At the same time the reduced sulfonated graphene oxide (rSGO), reduced graphene oxide (rGO), and graphene oxide (GO) were performed as the comparative samples. The results showed that the maximum adsorption capacities of SGO were 2530 mg/g for methylene blue and 415 mg/g for Pb2+, which was much higher than that of the contrast samples and adsorbents reported in literatures. The adsorption of SGO was investigated systematically including the saturated adsorption capacities, isotherm, and kinetic adsorption process. The SGO displayed high adsorption efficiency and superior adsorption capacity toward metal ions and dyes, which is mainly attribute to the good dispersibility and the multiple adsorption sites of SGO. These results are promising not only providing effective adsorbing heavy metal ions and organic dyes, but also gaining insights into adsorption mechanism of graphene materials.

Enhanced Proton Conductivity and Methanol Permeability Reduction via Sodium Alginate Electrolyte-Sulfonated Graphene Oxide Bio-membrane.

The high methanol crossover and high cost of Nafion® membrane are the major challenges for direct methanol fuel cell application. With the aim of solving these problems, a non-Nafion polymer electrolyte membrane with low methanol permeability and high proton conductivity based on the sodium alginate (SA) polymer as the matrix and sulfonated graphene oxide (SGO) as an inorganic filler (0.02-0.2 wt%) was prepared by a simple solution casting technique. The strong electrostatic attraction between -SO3H of SGO and the sodium alginate polymer increased the mechanical stability, optimized the water absorption and thus inhibited the methanol crossover in the membrane. The optimum properties and performances were presented by the SA/SGO membrane with a loading of 0.2 wt% SGO, which gave a proton conductivity of 13.2 × 10-3 Scm-1, and the methanol permeability was 1.535 × 10-7 cm2 s-1 at 25 °C, far below that of Nafion (25.1 × 10-7 cm2 s-1) at 25 °C. The mechanical properties of the sodium alginate polymer in terms of tensile strength and elongation at break were improved by the addition of SGO.

Conversion of lipids from wet microalgae into biodiesel using sulfonated graphene oxide catalysts.

Four solid acid catalysts including graphene oxide (GO), sulfonated graphene oxide (SGO), sulfonated graphene (SG), and sulfonated active carbon (SAC) were used to convert lipids in wet microalgae into biodiesel. The physiochemical properties of the catalysts were characterized with scanning electron microscope, X-ray diffraction, and thermogravimetric analysis. SGO provided the highest conversion efficiency (84.6% of sulfuric acid) of lipids to fatty acid methyl esters (FAME). Whereas SAC converted few lipids into FAME. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that much higher hydrophilic hydroxyl content in SGO catalyst resulted in a considerable higher conversion efficiency of lipids to FAME than that (48.6%) catalyzed by SG, although SO3H groups (0.44mmol/g) in SGO were less than those (1.69mmol/g) in SG. Given its higher SO3H group content than GO (0.38mmol/g), SGO had higher conversion efficiency than GO (73.1%), when they had similar hydrophilic hydroxyl contents.

Electrochemistry and electrocatalysis of myoglobin immobilized in sulfonated graphene oxide and Nafion films.

In this study, sulfonated graphene oxide (SGO) was synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was used to make Mb-SGO-Nafion composite films by coating myoglobin (Mb) on the glassy carbon electrodes (GCE). Positions of the Soret absorption bands suggested that Mb retained its native conformation in the films. Mb-SGO-Nafion film modified electrode showed a pair of well-defined and nearly reversible cyclic voltammetry peaks at around -0.39 V versus saturated calomel electrode (SCE) in pH 7.0 buffers, characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters such as electron transfer rate constant (ks) and formal potential (E(o')) were estimated by fitting the data of square-wave voltammetry with nonlinear regression analysis. Experimental data demonstrated that the electron transfer between Mb and electrode was greatly facilitated and showed good electrocatalytic properties toward various substrates, such as H2O2 and NaNO2, with significant lowering of reduction overpotential.

Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (µA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties.

Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic-hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm(-2) maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm(-2)) under 2 M methanol fuel at 70 °C.