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This paper investigates the effects of different amounts of N heteroatoms on the structural and electronic properties of pristine graphene and the adsorption behavior of Li atoms on N-doped graphene via first-principles calculations. The obtained results suggest that new N hexagonal structures are formed around the C hexagonal structure. The third-nearest neighbor structures are always maintained between the new N atoms and one of the original ones. Among the different N-doped graphene samples, the di- and tetra-N-doped and superlattice C3N exhibit semiconductor properties, while the others exhibit non-magnetic metallic properties. Studies on superlattice C3N reveal that N-doped graphene does not exhibit the aggregation of Li adatoms typical of pristine graphene. Single Li and two Li adatoms show non-magnetic metallic properties and semiconductor properties, respectively. The formation of multiple N-doped graphene samples explains the physical formation process of superlattice C3N. Their corresponding electronic properties and Li adsorption behavior are expected to motivate graphene applications in gas storage and sensing, catalysts, and biological devices. [ABSTRACT FROM AUTHOR]

We have systematically explored the electronic structures and magnetic properties of metal Pd, Pt, Cu, Ag, Au and Zn adsorbed MoSe 2 monolayer by means of first-principles calculations. It reveals that stable chemical adsorption has been formed between the adatoms Pd, Pt, Cu, Ag, Au and MoSe 2 monolayer, however, weak physical interaction is found between Zn and MoSe 2 monolayer owing to the small adsorption energy. Both the framework structure and electronic property of the metal adsorbed MoSe 2 monolayer are slightly tuned by the adatoms. More importantly, magnetic character is introduced in Cu, Ag and Au systems. [ABSTRACT FROM AUTHOR]

An electroactive hybrid film composed of amorphous α-zirconium phosphate and polyaniline (α-ZrP/PANI) is controllably synthesized on carbon nanotubes (CNTs) modified Au electrodes in aqueous solution by cyclic voltammetry method. Electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM) and X-ray power diffraction (XRD) analysis are applied for the evaluation of the synthesis process. It is found that the exfoliated amorphous α-ZrP nanosheets are well dispersed in PANI and the hydrolysis of α-ZrP is successfully suppressed by controlling the exfoliation temperature and adding appropriate supporting electrolyte. The insertion/release of heavy metals into/from the film is reversibly controlled by a potential-triggered mechanism. Herein, α-ZrP, a weak solid acid, can provide an acidic micro-environment for PANI to promote the electroactivity in neutral aqueous solutions. Especially, the hybrid film shows excellent potential-triggered adsorption of Pb 2+ ion due to the selective complexation of Pb 2+ ion with oxygen derived from P O H of α-ZrP. Also, it shows long-term cycle stability and rapid potential-responsive adsorption/desorption rate. This kind of novel hybrid film is expected to be a promising potential-triggered ESIX material for separation and recovery of heavy metal ions from wastewater. [ABSTRACT FROM AUTHOR]

The adsorption equilibrium isotherms of three aromatic sulfonic acid compounds, 2-naphthalenesulfonic acid, p-toluenesulfonic acid and p-chlorobenzenesulfonic acid, from aqueous solutions by maeroporous weak base anion exchanger within the temperature range of 293 K-313 K were obtained. Several isotherm equations were correlated with the equilibrium data, and the experimental data was found to fit the three-parameter Redlich-Peterson equation best within the entire range of concentrations. The study showed that the hydrophobicity of solute has distinct influence on adsorption capacity of the anion exchanger for the aromatic sulfonic acid. Moreover, estimations of the isosteric enthalpy, free energy, and entropy change of adsorption were also reported. The positive isosteric enthalpy and entropy change for adsorption indicate an endothermic and entropy driven process in the present study. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption equilibrium isotherms of phenolic compounds, phenol, p-cresol, p-chlorophenol and p-nitrophenol, from aqueous solutions by Amberlite XAD-4 polymeric adsorbent and its acetylized derivative MX-4 within temperature range of 283-323K were obtained and fitted to the Freundlich isotherms. The capacities of equilibrium adsorption for all four phenolic compounds from their aqueous solutions increased around 20% on the acetylized resin, which may be contributed to the specific surface area and the partial polarity on the network. Estimations of the isosteric enthalpy, free energy, and entropy for the adsorption process were reported. [ABSTRACT FROM AUTHOR]

• The adsorption stability of monomers and polymers on quartz surfaces was analyzed by molecular simulation and found that the adsorption stability of monomers could predict the adsorption stability of polymers. • The adsorption of polyacrylamide with different degrees of polymerization on the quartz surface was constructed. The results showed that there was adsorption saturation on the quartz surface. • The effect of different temperatures on polymer adsorption was simulated and it was found that temperature inhibits the adsorption stability of polymers. • Analyzing the adsorption of PAM in the quartz pores under vacuum and in solution, it was found that the effect of water molecules was not negligible. In fracturing stimulation, the adsorption of thickening agent molecules will cause reservoir damage, which will affect the fracturing stimulation performance. Therefore, it is very important to study the influencing factors of the adsorption of polymer molecules on the rock surface to reduce the polymer adsorption damage. In this paper, we simulated the adsorption behavior of modified polyacrylamide on the quartz surface to investigate the polymer adsorption on the sandstone. The shear properties of polyacrylamide (PAM) solution were studied using molecular dynamics. The adsorption energy, mean square displacement, radial distribution function, etc. were calculated in this work. Then, the adsorption behavior of PAM molecules on the quartz surface was analyzed. The adsorption of PAM on the quartz surface is mainly through the hydrogen bonding force formed between amide groups of PAM and hydroxyl groups of the quartz surface. Hydrogen bonds are easily broken at high temperatures. Therefore, the adsorption stability of PAM molecules will reduce with the increase in temperature. Moreover, the influence of modified monomers AA and AMPS on the adsorption stability, adsorption mechanism, and viscosity of the PAM solution under different conditions was studied. The shear simulation showed that modified monomers of AA and AMPS had a certain enhancement action on the viscosity of the PAM solution. However, stability studies revealed that adsorption damage will also increase accordingly. The research results provided some theoretical references for the development of low-damage fracturing fluid for ultra-low permeability reservoirs in the future. [ABSTRACT FROM AUTHOR]

A novel approach to the negatively charged hybrid adsorbents was proposed. These hybrid adsorbents were prepared via the ring opening of pyromellitic acid dianhydride (PMDA) and N-[3-(trimethoxysilyl)propyl]ethylenediamine and a subsequent sol–gel process. Fourier transform infrared spectra confirmed the step products. Their adsorption kinetics, isotherm, and thermodynamic parameters ΔG, ΔH, and ΔSfor Pb2귩ꢽ from aqueous solution were examined. Differential scanning calorimetry and thermogravimetric analysis thermal amylases showed that these samples had high thermal stability and the crystallization temperature increased with an increase in the PMDA content because of cross-linking between organic and inorganic moieties and the further formation of a hybrid matrix. Adsorption experiments indicated that Pb2槛⢮魢 on these hybrid adsorbents followed the Lagergren second-order kinetic and Langmuir isotherm models. The negative values of ΔGand the positive values of ΔHshowed that Pb2槛⢮魢 on these hybrid adsorbents was spontaneous and an endothermic process in nature. Scanning electron microscopy and energy-dispersive spectrometry images further confirmed Pb2誉 on the surfaces of samples A–D. Moreover, a desorption experiment indicated that they can be regenerated. These findings suggest that the prepared hybrid adsorbents are promising in the separation and recovery of Pb2誉 from contaminated water. [ABSTRACT FROM AUTHOR]

The focus of this work is to control the structure of electrosprayed polymer microspheres and then study the effect of different structures on the microspheres' adsorption properties. Scanning electron microscopy (SEM) coupled with image analysis software was employed to evaluate the size distributions and the structure of microspheres. According to the observation and analysis results, two types of polyethersulfone (PES) porous microspheres (perfect sphere-shaped and collapsed) were prepared via electrospraying technology by adjusting the solvent and polymer molecular weight. The porous PES microspheres can remove bisphenol A (BPA) from its aqueous solution effectively. Compared with collapsed microspheres, the rough microspheres had much higher specific surface area and better mobility in the BPA aqueous solution, so it showed a better adsorption capacity than that of collapsed microspheres. The solvent evaporation rate and the occurrence rate of phase separation significantly affect the structure and morphology of microspheres. [ABSTRACT FROM AUTHOR]

[Display omitted] • CH 4 /N 2 adsorbents were prepared by simple zeolite Y ion-exchange with amine cations. • CH 4 uptakes of decorated zeolite Y increased greatly whereas the N 2 uptakes decreased. • CH 4 /N 2 separation performances of decorated zeolite Y were greatly improved. • Resulting decorated zeolite Y also exhibited good regenerability and stability. Adsorption based process for CH 4 /N 2 separation is promising and attractive while it remains a challenge endeavor due to the lack of efficient adsorbents. In this work, amine ion-exchanged Y zeolites were developed for CH 4 /N 2 separation. By simple ion-exchanged with tetramethylammonium cation (TMA+) and choline cation (Ch+), CH 4 adsorption amounts of the resulting adsorbents were obviously increased while their N 2 adsorption amounts were significantly decreased. Consequently, CH 4 /N 2 separation performances of resulted samples were greatly improved compared to pristine NaY. CH 4 /N 2 selectivities of resulting sample TMAY and ChY were up to 6.32 and 6.50, respectively, at 25 °C and 100 kPa. Monte Carlo calculations were used to study the interaction affinity for CH 4 and N 2 on the adsorbents. Breakthrough experiments were further confirmed the excellent separation performances of TMAY and ChY. The excellent separation performances of the resulting adsorbents verified the efficiency of the simple ion-exchange strategy and the application potential of the adsorbents. [ABSTRACT FROM AUTHOR]

A series of spherical activated carbons (SACs) with different pore structures were prepared from chloromethylated polydivinylbenzene by ZnCl2 activation. The effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied. All the SACs are generated with high yield of above 65% and exhibit relatively high mesopore fraction (me%) of 35.7%–43.6% compared with conventional activated carbons. The sample zlc28 prepared at 800°C for 2 h has the largest BET surface area of 891 m2 g-1 and pore volume of 0.489 cm3 g-1. SEM and XRD analyses of zlc28 verify the presence of developed porous structure composed of disordered micrographite stacking with large amounts of interspaces in the order of nanometers. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption behavior of p-aminobenzoic acid and o-aminobenzoic acid onto the different polymeric adsorbents was systematically investigated as a function of the solution concentration and temperature. Experimental results indicated that the equilibrium adsorption data of the four polymeric adsorbents fitted well in the Freundlich isotherm. The adsorption capacity of multi-functional polymeric adsorbent NJ-99 was the highest, which might be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of aminobenzoic acid. The adsorption capacity of o-aminobenzoic acid onto any adsorbent was higher than p-aminobenzoic acid. Thermodynamic studies suggested the exothermic, spontaneous physical adsorption process. Adsorption kinetics results showed that the adsorption followed the pseudo-second-order kinetics model and the intraparticle mass transfer process was the rate-controlling step. [Copyright &y& Elsevier]

Abstract: Two novel polymers (NJ-1 and NJ-2) were synthesized by chemically modified a hypercrosslinked polymer NJ-0 with dimethylamine and trimethylamine, respectively. The comparison of the adsorption properties of the three polymers toward phenol, resorcin and phloroglucin was made. The study focused on the static equilibrium adsorption behaviors and the adsorption thermodynamics. Freundlich equation was found to fit the adsorption results well. The effect of amino groups introduced onto the surface of the resin and the structure of phenolic compounds on the adsorption were also studied. The hydrogen-bonding interaction and electrostatic interaction could happen between the amino groups and the adsorbates. The adsorption impetus increased as quantity of hydroxyl groups increased, but the adsorption capacity decreased due to the drop of the matching degree of the aperture of resins and the diameter of adsorbate molecules. [Copyright &y& Elsevier]

Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate. [ABSTRACT FROM AUTHOR]

The adsorption behaviors of 2-naphthalenesulfonic acid and aniline on a conventional macroporous resin Amberlite XAD4 and the other two newly-developed hypercrosslinked resins NDA101 and NDA100 were investigated in a single or binary batch system at 293 K and 313 K, respectively. All the adsorption isotherms of 2-naphthalenesulfonic acid and aniline on the test resins in both systems can fit well with the Langmuir equation, indicating that the adsorption is a favorable process. At the identical equilibrium concentration, the amount of aniline adsorbed on polymeric resins in the single system is higher than that in the binary system because of the competitive adsorption between 2-naphthalenesulfonic acid and aniline on the resin surface. However, the uptake amount of 2-naphthalenesulfonic acid in the binary system is markedly larger than that in the single system, which is presumably due to the cooperative effect arisen from the electrostatic interaction between 2-naphthalenesulfonic acid and aniline adsorbed on the resin surface. The simultaneous adsorption system was proven to be helpful for the selective adsorption toward 2-naphthalenesulfonic acid due to its larger selective index. [ABSTRACT FROM AUTHOR]

An aminated hype rcrosslinked macroporous polymeric adsorbent was synthesized and characterized. Adsorption isotherms for 1-amino-2-naphthol-4-sulfonic acid (1, 2, 4-acid) and 2-naphthol obtained from various binary adsorption environments can be well fitted by Freundlich equation, which indicated a favorable adsorption process in the studied range. Adsorption for 1, 2, 4-acid was an endothermic process in comparison with that for 2- naphthol of an exothermic process. 2-naphthol molecules put a little influence on the adsorption capacity for 1, 2, 4- acid. However, the adsorption to 1, 2, 4-acid depressed that to 2-naphthol in a large extent for the stronger electrostatic interaction between 1, 2, 4-acid and adsorbent. The predominant mechanism can be contributed to the competition for adsorption sites. And the simultaneous environment was confirmed to be helpful to the selective adsorption towards 1,2,4-acid based on the larger selectivity index. [ABSTRACT FROM AUTHOR]

• CoWO 4-x @C exhibits comparable HER activity to Pt/C in acidic and alkaline mediums. • CoWO 4-x @C requires only 295 mV overpotential to deliver 10 mA cm−2 in the OER test. • 1.57 V is required for CoWO 4-x @C to attain 10 mA cm−2 in alkaline water splitting. Development of earth-abundant, efficient and stable electrocatalysts for water splitting is of crucial importance for environmentally friendly energy conversion and storage. Here, we report an oxygen deficient cobalt tungstate nanoparticles with diameter of 8 nm (CoWO 4-x @C) as efficient bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen reduction reaction (OER), which exhibits comparable HER activity to commercial Pt/C with overpotentials of 32.5 mV and 46.8 mV vs. RHE to deliver current density of 10 mA cm−2 in acidic and alkaline mediums, respectively, ascribed to the rich oxygen vacancies facilitating the hydrogen adsorption and its relative recombination, respectively. Additionally, undetectable degradation is observed for CoWO 4-x @C after 10,000 potential cycles indicating high durability. Meanwhile, CoWO 4-x @C requires only 295 mV overpotential to deliver 10 mA cm−2 in the OER test, which is better than the benchmarking IrO 2 (313 mV). 1.57 V comparably lower than Pt/C-IrO 2 (1.59 V) is required for achieving the water splitting current density of 10 mA cm−2 without any degradation for 12 h. [ABSTRACT FROM AUTHOR]