Synthesis, characterization and catalytic application of a novel ethyl and boron sulfonic acid based bifunctional periodic mesoporous organosilica
Abstracts:A novel ethyl and boron sulfonic acid based bifunctional periodic mesoporous organosilica [BPMO-Et-B(OSO3H)2] with dual Lewis-protic acidic sites was prepared, characterized and applied as efficient nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans. The BPMO-Et-B(OSO3H)2 was prepared by the chemical attachment of boric acid [B(OH)3] on an ethyl-based periodic mesoporous organosilica (PMO-Et) followed by treatment with chlorosulfonic acid (ClSO3H) at room temperature. This nanocatalyst was characterized using Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), low-angle powder X-ray diffraction (LAPXRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). The BPMO-Et-B(OSO3H)2 was shown to be a highly efficient nanocatalyst for three-component synthesis of tetrahydrobenzo[b]pyran derivatives at room temperature under solvent-free conditions. Moreover, the BPMO-Et-B(OSO3H)2 was recovered and reused at least 8 times without significant decrease in its activity.
Influence of casting solvents on sedimentation and performance in metal–organic framework mixed-matrix membranes
Abstracts:Mixed matrix membranes (MMMs) for gas separation is a promising application and has received much attention. The construction of membranes ultimately decides the performance of the membrane, with the underlying interaction between fillers and polymer playing the most important role concerning pathways for gas molecules. In this study, we compared the interactions between the metal–organic framework MIL-53(Al) and polysulfone (PSF) in MMMs with various concentrations of PSF in two different casting solvents chloroform and tetrahydrofuran (THF). We detail the preparation of membranes with varying degrees of sedimentation, subsequent analysis, and gas permeation performance.
Reduced graphene oxide supported raspberry-like SrWO4 for sensitive detection of catechol in green tea and drinking water samples
Abstracts:The raspberry-like strontium tungstate microspheres supported on reduced graphene oxide nanosheets (rGOSs@SrWO4) were prepared by a hydrothermal method and it was applied to the electrocatalytic sensing of catechol. The as-prepared rGOSs@SrWO4 composite was characterized by XRD, Raman, FESEM, EDX, EIS, and voltammetric techniques. Morphology studies reveal the uniform wrapping of raspberry-like SrWO4 microstructure by thin sheets of rGOSs and the composite possesses large surface area and abundant catalytic active sites. The rGOSs@SrWO4 composite modified screen-printed multi-conventional electrode (SPME) was fabricated which was found to exhibit extraordinary electrocatalytic activity and excellent selectivity towards the detection of catechol. The rGOSs@SrWO4/SPME displayed a linear range of 0.034–672.64 µM and detection limit of 7.34 nM using differential pulse voltammetry as signal read-out. Furthermore, the electrode was durable, reproducible and repeatable. The practical utility of the method was demonstrated in green tea and drinking water samples.
Functionalization of MWCNTs by plasma treatment and use as conductive additives for LiFePO4 electrode
Abstracts:The application of LiFePO4 in high power battery is limited by its low conductivity. MWCNTs as conductive additives were functionalized with maleic anhydride (MA) using the plasma-induced grafting technique. A series of LiFePO4/MWCNTs-MA composite electrodes with 1.7 wt%, 2.7 wt%, 4.7 wt%, and 9.7 wt% of MWCNTs-MA were fabricated to improve conductivity and to investigate the effects of MWCNTs-MA on LiFePO4 electrode performance. X-ray diffraction analysis of LiFePO4/MWCNTs-MA cathodes showed that crystallinity and lattice spacing of LiFePO4 were not altered by incorporation of MWCNTs-MA. Field-emission scanning electronic microscopy showed that 4.7 wt% MWCNTs-MA dispersed well in LiFePO4 particle matrix. Electrochemical impedance spectroscopy showed that charge transfer resistance was decreased by increased amount of MWCNTs-MA. The specific capacity, cyclic stability, and rate performance of LiFePO4 coin cells were enhanced by increased amount of MWCNTs-MA, and reaching optimal performance at 4.7 wt%. The LiFePO4/MWCNTs-MA (4.7 wt%) battery had rate capacity of 114 mAh g−1 at 1 C with a capacity retention ratio of 75.6% after 200 cycles.
Insights into high-efficiency molecularly imprinted nanocomposite membranes by channel modification for selective enrichment and separation of norfloxacin
Abstracts:A facile, yet efficient method was proposed here to prepare the novel molecularly imprinted nanocomposite membranes (MICMs) with high adsorption capacity and rapid selective separation aiming at targeting norfloxacin. The MICMs were prepared by vacuum filtering directly pre-synthesized norfloxacin-imprinted nanocomposites to the regenerated cellulose membranes, which utilized adequately the dual-function effect of dopamine as crosslinking agent and functional monomer. Moreover, the best adsorption capacity and separation factor of MICMs toward target can reach up to 25.35 mg/g and 4.43, respectively, which were far superior to that of non-imprinted nanocomposite membranes (NICMs) (6.38 mg/g and 1.0, respectively). Meanwhile, the perm-selectivity (the permeability factor β values were also more than 15.2). And this work provided an exemplary guidance for the treatment of fluoroquinolones antibiotics pollutants in water environment.
Kinetics of reactive absorption of CO2 using aqueous blend of potassium carbonate, ethylaminoethanol, and N-methyl-2-Pyrollidone (APCEN solvent)
Abstracts:Employing the fall in the CO2 pressure method, the kinetics of the reactive absorption of CO2 in the aqueous blend of potassium carbonate, ethylaminoethanol, and N-methyl-2-Pyrollidone (APCEN solvent) is inspected by altering the amine concentration and the absorption temperature. The rate of the absorption of CO2 and the solubility/diffusivity of CO2 in the APCEN solvent is ascertained by using a stirred cell reactor. Based on the obtained experimental findings, the order of the absorption for CO2 in the APCEN solvent is estimated and understood to be of overall second order (1st order with respect to both EAE and CO2, respectively). The rate of the absorption of CO2 in the APCEN solvent is observed to be noticeably higher than the APCE solvent (aqueous potassium carbonate promoted by ethylaminoethanol) and numerous other secondary amines. For instance, at 303 K (with EAE concentration equal to 1.5 kmol m−3), the rate of the absorption of CO2 in the APCEN solvent is 18.8% higher than the APCE solvent. By studying the effect of the absorption temperature, the activation energy for the APCEN solvent is determined and viewed to be equivalent to the APCE solvent. Furthermore, the lumped parameter in case of the APCEN solvent is higher (1.41 × 10− 6 kmol1/ 2 m−1/ 2 s− 1 kPa−1) as compared to the APCE solvent (1.2 × 10− 6 kmol1/ 2 m−1/ 2 s− 1 kPa−1). In total, the rate of absorption of CO2 in the APCEN solvent is considerably higher than that of the APCE solvent, and other secondary amines such as methylmonoethanolamine (MMEA), propylmonoethanolamine (PMEA), and butylmonoethanolamine (BMEA).
Correlation between phase structure and electrochemical properties of Ce2Ni7-type La-RE-Mg-Ni (RE = Nd, Sm, Y) alloys: A comparative study
Abstracts:The correlation between phase structure and electrochemical properties of La0.83Mg0.17Ni3.1Co0.3Al0.1 was investigated firstly by partial substitution of La with Sm. It was found that the La0.83-xSmxMg0.17Ni3.1Co0.3Al0.1 alloy consists mainly of the Ce2Ni7-type phase, the abundance of which reaches the maximum (92.23 wt.%) at x = 0.2 when x is changed from 0 to 0.4. The alloy containing more Ce2Ni7-type phase exhibited the better the cyclic and high rate discharge ability examined by electrochemical measurements, i.e. the best electrochemical performance was confirmed at x = 0.2. Furthermore, the influence of unit cell volumes of the Ce2Ni7-type main phase on electrochemical properties was investigated systematically based on the comparison of substitution effect of Sm, Nd and Y for La at x = 0.2. Compared to those of Nd- and Y-substitutions, the Sm-substituted alloy containing Ce2Ni7-type main-phase showed better overall electrochemical properties, especially Cmax = 393.3 mAh g–1 and S100 = 87.2%. Such superior electrochemical performance may result from appropriate cell volumes and anti-pulverization abilities.
Three-dimensional magnetic graphitic carbon nitride composites as high-performance adsorbent for removal Pb2+ from aqueous solution
Abstracts:Three-Dimensional magnetic nanocomposite (Fe3O4@g-C3N4) was first prepared and used to removal Pb2+ from aqueous solution by adsorption method. Various of techniques were used to character Fe3O4@g-C3N4 such as scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermo-gravimetric analyzer (TGA). Batch experiments with different pH, initial concentration, contact time and ionic strength were used to evaluate the adsorption performance of Fe3O4@g-C3N4. The adsorption kinetics data followed pseudo-second-order model. The isothermal adsorption equilibrium data were best described by Langmuir model and predicated adsorption capacity was 423.73 mg g−1 for Pb2+. The result of X-ray photoelectron spectroscopy (XPS) survey spectrum suggested that the main adsorption mechanism of Fe3O4@g-C3N4 for Pb2+ is the coordination between conjugated π-electron pairs of heptazine (C6N7) units or triazine ring (C3N3) units and sp2 CN with metal ions. By comparing the adsorption capacities of Fe3O4, g-C3N4 and Fe3O4@g-C3N4, it can be found that the adsorption capacity of g-C3N4 would increase by increasing the layer spacing. Fe3O4@g-C3N4 could be regenerated by HNO3 and the adsorption capacity of regenerative Fe3O4@g-C3N4 could maintain 89.3% after five cycles. The adsorption capacity of Fe3O4@g-C3N4 for Pb2+ is 121.42 mg g−1 in acid electrolytic zinc residue percolate. Therefore, the Fe3O4@g-C3N4 is a potential adsorbent for removing Pb2+ from wastewater.
A strategy for effective cesium adsorption from aqueous solution by polypentacyanoferrate-grafted polypropylene fabric under γ-ray irradiation
Abstracts:For both cesium resources and human health, it is crucial to develop novel materials for effective separation of cesium from aqueous solutions. We report herein a new approach to separate cesium from aqueous solutions using poly(pentacyanoferrate)-functionalized polypropylene nonwoven fabric. To obtain the adsorbent, poly(4-vinyl pyridine) (P4VP) was first grafted onto polypropylene nonwoven fabric under γ-ray irradiation, and then reacted with sodium pentacyanoaminoferrate. Adsorption kinetically follows a pseudo-second-order model and achieves equilibrium within 24 min at pH 7.0 and 298.15 K. To the best of our knowledge, it is the fastest adsorption of cesium ions from aqueous solution till now. The maximum adsorption capacity calculated from Langmuir equation was 47.4 mg/g with high selectivity. Adsorption mechanism involves the formation of coordination and covalent bond between cesium and cyano group. In addition, the adsorbent could be regenerated effectively after four cycles with 0.1 M NaOH as a desorbing agent. It is noticed that the covalent combination of functional ligands with nonwoven fabric may improve the practical operability in comparison with nano-adsorbents. This work indicates that the functional fabric may be a promising adsorbent to achieve effective removal of cesium ions from aqueous solutions.
Making of a metal-free graphitic carbon nitride composites based on biomass carbon for efficiency enhanced tetracycline degradation activity
Abstracts:In this paper, a new metal-free photocatalyst (g-C3N4/C) coupled by graphitic carbon nitride (g-C3N4) and biomass carbon (waste paper used as carbon source) has been successfully synthesized. The g-C3N4/C exhibits obviously improved photocatalytic activity for degrading tetracycline, the degradation rate is more than 80%. It is more than four times than that of pure g-C3N4. Based on the structure and morphology characterization, the as-prepared g-C3N4/C represents a porous structure, which can provide a large surface area, increase the transmission route of photo-generated carriers and suppress the charge recombination. In addition, the capture experiments and ESR exploration show that both the h+, ·OH and ˙O2 −play the important roles in this metal-free photocatalytic reaction. More importantly, our work not only designs a better photocatalytic material, but also provides a new thinking for, waste recycling which coincides with the concept of sustainable development