Quantitative Analysis of Cd 2+ Adsorption–Desorption and Interparticle Interactions by Single‐Entity Electrochemistry

Adsorption kinetics, isotherms and thermodynamics of Cr(III) on graphene oxide

Single-entity electrochemistry (SEE) provides powerful means to track a single particle, single cell, and even single molecule from the nano to microscale. The electrode serves as not only the detector of collision but also the surface supplier in SEE, and the fundamental understanding of the electrode surface chemistry on the dynamic particle-electrode interactions and electrochemical responses of a single particle still remains unexplored, particularly for soft particles. Herein, dynamic interactions of microemulsions and the interaction-controlled electron-transfer (ET) kinetics are studied employing SEE and fluorescence spectroscopy. The o/w-type nitrobenzene emulsions were prepared with the surfactant-type room temperature ionic liquids (RTILs). Biased the electrode potential for the reduction of 7,7,8,8-tetracyanoquinodimethane within emulsions, it is surprising to see the distinct collision current signals on the carbon fiber ultramicroelectrode (C UME) and Au ultramicroelectrode (Au UME) in the late stage of chronoamperometric measurements. Theoretical understanding was made to determine the ET kinetics behind the disparate current signals. It is believed that the electrode surface chemistry, i.e., the surface energy, has a great influence on the dynamic emulsion-electrode interactions and ET kinetics. On the hydrophilic surface of Au UME, emulsions tend to decompose/detach from the electrode surface immediately after colliding. In contrast, on the lipophilic surface of C UME with lower surface energy, a layer of oil phase accumulated by the coalescence of emulsions and the migration of the precedent colliding emulsions, which would serve as a barrier to block ET via tunneling as manifested by the gradual slowdown of ET rate and the reduced collision frequency in the late stage of measurement. The impacts of the emulsion size and amphiphilicity of RTILs on the C UME-emulsion interactions and ET kinetics were also investigated.

Synthesis and adsorption performance of Mg(OH)2 hexagonal nanosheet–graphene oxide composites

We used electrostatic force microscopy (EFM) to investigate local conducting states of atomically thin individual graphene oxide (GO) sheets and monitor the spatial evolution of their conducting properties during the reduction process. Because of the thinness of the GO sheets and finite carrier density, the electric field is partially screened in the reduced GO, which is manifested in the EFM phase signals. We found inhomogeneous oxidation states in as-prepared GO sheets and followed the evolution of reduction process in the individual GO sheets during both thermal and chemical reduction. We also compared the EFM measurement results with simultaneous IV characteristics to assess correlations between two measurements.

In order to deal with the increasingly serious pollution of graphene oxide (GO) to the environment. In this paper, the use of red sandstone to treat GO-contaminated aqueous solution is proposed for the first time, and the adsorption capacity and adsorption mechanism of red sandstone to GO are discussed. The controlled variable method was used to explore the optimal pH, concentration, and quality of red sandstone for GO aqueous solution. The adsorption isotherm, thermodynamics, and adsorption kinetics were fitted. Adsorption characterization tests were performed using XRD, AFM, XPS, FT-IR, SAP, TEM, SAP, laser particle size analyzer, and SEM. The results show that when [Formula: see text], the optimum adsorption condition of red sandstone for GO is [Formula: see text], the mass of the adsorbent is 40 mg, and when the concentration of GO is 80 mg/L, the adsorption capacity is 90 mg/g. The adsorption isotherm model fits the Langmuir model. The adsorption thermodynamic experiments and fitting results show that the reaction is endothermic. XRD and FT-IR tests showed that CaCO 3 in red sandstone was involved in the adsorption of GO. SEM, TEM, and AFM microscopic results showed that GO was adsorbed on the surface of red sandstone particles. The XPS test showed that Ca 2+ in red sandstone and C=O bond in GO undergo ionic or coordination reaction. The adsorption kinetics fit a pseudo-second-order kinetic model. This study will provide some references for the removal of GO in the environment and the interaction mechanism with natural minerals.

Kinetics and thermodynamics of mercury adsorption onto thiolated graphene oxide nanoparticles

Excellent mechanical, electrical, and thermal properties of graphene have been achieved at the macroscale by assembling individual graphene or graphene oxide (GO) particles. Wet-spinning is an efficient and well-established process that can provide GO assemblies in fiber form. The coagulation bath in the wet-spinning process has rarely been considered for the design of mechanically robust GO fibers (GOFs). In this study, locating the amidation reaction in the coagulation bath yielded mechanically improved GOFs. The imides 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide were used to form covalent amide bonds between GO flakes and chitosan, thereby reinforcing the GOFs. Evidence and effects of the amidation reaction were systematically examined. The tensile strength and breaking strain of the GOFs improved by 41.6% and 75.2%, respectively, and the toughness almost doubled because of the optimized crosslinking reaction. Our work demonstrated that using a coagulation bath is a facile way to enhance the mechanical properties of GOFs.

Fabrication of graphene oxide composite membranes and their application for pervaporation dehydration of butanol

Tuning interlayer spacing of graphene oxide membrane to enhance its separation performance of hydrogen isotopic water in membrane distillation

Although poly(vinyl alcohol) (PVA) membranes are widely used in solvent dehydration by pervaporation, the separation factor is rather limited. Considering this, novel PVA mixed matrix membranes with graphene oxide (GO) nanosheets were prepared. poly(acrylonitrile) ultrafiltration (PAN) membrane was used as support layer. The PVA/GO composite membranes were characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, thermogravimetric analysis and water contact angle. We also explored the pervaporation performance of the membrane for ethanol dehydration. GO slightly improves the thermal stability and crystallinity of the composite membranes. In addition, the hydrophilicity of the composite membranes is weakened after GO addition, but the crosslinking degree is increased, resulting a significant increase in the separation factor and a certain decrease in the total flux. With the amount of GO addition increases, the total flux of the PVA/GO composite membrane decreases, while the separation factor increases first and then decreases, and the preferred amount of GO addition is 2.0 wt%. Especially, the separation factor of the composite membranes with 2.0 wt% GO addition could reach 3 059, which is 16 times higher than PVA membranes, with the corresponding permeability flux is 145 g m−2 h−1.

High-efficiency water-transport channels using the synergistic effect of superhydrophilic PA layer and robust BU cross-linked GO laminates

Adsorption and release profile analysis of oxytetracycline drug on functionalized graphene oxide nanoparticles

Adsorption and removal of tetracycline antibiotics from aqueous solution by graphene oxide

RETRACTED: The highly efficient adsorption of Pb(II) on graphene oxides: A process combined by batch experiments and modeling techniques

The properties of graphene enriched silk depend on the amount of graphene oxide (GO) adsorption on silk. GO dipping parameters include the GO solution pH, initial GO concentration, dipping time and temperature, and the type of substrate. The effects of GO dipping parameters on the sorption process are studied to achieve the maximum GO adsorption on the silk surface for the preparation of an economical graphene/silk-based textile product. In addition, equilibrium isotherms, kinetics, and thermodynamics of GO adsorption on the silk surface in a batch sorption process are examined to understand the adsorption mechanism. The Freundlich isotherm best describes the adsorption of GO onto the silk. A pseudo-second order kinetic model best describes the kinetics of GO adsorption. Thermodynamic studies reveal that GO adsorption is spontaneous and exothermic.