查看更多>>摘要：In this work,naphthalimide derived functionalized silica material SiO2@NAPIA(2,2'((((propylazanediyl)bis(methylene))bis(2,l-phenylene))bis(oxy was constructed as a dual signaling and remediation material for ferric ions from a pool of 35 common ions(cations and anions)in the aqueous system.The material Cubic SiO2 shows a high surface area(1104 m~2/g,pore volume(1.510 cm~3/g),and pore diameter(6.3 nm)in the mesoporous range,which reduces further on functionalization to get the final material SiO2@NAPIA.The ferric ion selectivity through fluorescence quenching displays a Stern-Volmer quenching constant(K_(SV))of 7.8 × 10~8 M~(-1)with a LOD(Limit of detection)value of 0.11 μM for ferric-ion,which is 48 times lower than the USEPA(United States Environmental Protection Agency)maximum contaminant level(5.35 μM)in drinking water.This material also shows a very high adsorption capacity(664 mg/g)for ferric ions fitting the Langmuir model isotherm with R~2 = 0.99,which can be easily stripped out,and the material can be recycled.This material was also used as a sensory probe material for biosensing of ferric ions through fluorescence imaging in living organisms like Artemia salina and quantification in the real environmental sample.Furthermore,the antibacterial activity inspired by the ferric ion chelating affinity shows good potency against several Gram-negative and Gram-positive bacterial strains.The Minimum Inhibitory Concentration(MIC)& Minimal Bactericidal Concentration(MBC)of the material against these pathogens were found to be 100 & 200 |ig/mL respectively.This material signifies superior activity with respect to the ferric-ion selective materials known in the literature.
查看更多>>摘要：A long alkyl chain-containing organosilica layer obtained from 1,8-bis(triethoxysilyl)octane(BTESO)was used to modify silicalite-1 membranes via a sol-gel method to obtain bi-layered BTESO/silicalite-1 composite membranes on macroporous α-Al2O3 supports for the recovery of diluted ethanol by pervaporation.Silicalite-1 zeolite membranes were hydrothermally synthesized using two seeding methods: those prepared using wet-rubbing seeding method exhibited larger separation factors than those obtained using the dip-coating method in the pervaporation of ethanol/water due to the thinner seed layer in the former.After modified with BTESO,the surface became smoother and denser with higher hydrophobicity,and the thickness of BTESO layer was approximately 300 nm on both types of membranes.In pervaporation,two types of silicalite-1 membranes unexpectedly showed similar performances after BTESO modification.Ethanol flux increased or was maintained while water flux decreased greatly for silicalite-1 membranes after BTESO coating with increasing sol concentrations,and a higher separation factor was attained without sacrificing ethanol flux.The long alkyl chains in BTESO and silanols reacted with hydroxyl groups in silicalite-1 provided flexibility and hydrophobicity for ethanol transport with minor resistance.The optimized 2.0% BTESO/silicalite-1 membranes synthesized using wet-rubbing method showed a maximum flux of 6.84 kg m~(-2)h~(-1)and separation factor of 24.6 with overall pervaporation separation index of 161 in the pervaporation of 5.0 wt% ethanol/water mixture at 60 ℃.
查看更多>>摘要：Oil spill cleanup has aroused increasing concern in environmental protection,which makes the development of a low-cost absorbent with good hydrophobicity to be a task of high practical significance.In this work,a novel and highly hydrophobic absorbent based on natural clay minerals was prepared and used for oil removal from water.The originally hydrophilic sepiolite was modified by tetraethyl orthosilicate(TEOS)and hexadecyltrimethox-ysilane(HDTMS)through a one-pot direct modification.The pristine and modified sepiolite(MS)were characterized for hydrophobicity,morphology,and composition.The results showed that the modify agent was successfully grafted onto the sepiolite surface,improved the roughness and disaggregation of fibers.And MS exhibited higher contact angle compared to the pristine sample.The diesel oil removal efficiency of MS was significantly higher compared to pristine sepiolite.The surface roughness and high hydrophobic properties played important role in the retention of oil from water.This study presented a facile method to produce promising absorbent based on clay minerals with excellent properties for oil spill cleanup.
查看更多>>摘要：We encapsulated selenium(Se)into AFI and LTA zeolites via Se vapour adsorption at-450 ℃ and studied Raman and optical absorption spectra(RS and OAS,respectively)of zeolite single crystals with incorporated Se.At high Se loading density(D),Se8 rings are formed in the AFI channels along with Se chains.The rings are oriented by their 4-fold axis parallel to channels.Se8 is also formed in the LTA large cavities with its 4-fold axis oriented parallel to the 4-fold axis of LTA at any D up to ~8 Se atoms per cavity(at/c).However,at D > 0.5 at/c,nearly unexplored Se_(12)rings oriented by their 3-fold axis parallel to the LTA 3-fold axis are formed along with Se8 in neighboring cavities.We discriminate between Se8 and Se_(12)rings via 1)RS frequencies; 2)RS and OAS band intensities vs.D; 3)RS band intensities vs.excitation wavelength and light polarization configuration.With an increase in D,the number of Se_(12)rings grows faster than that of Se8.We extract OAS of Se8 and Se_(12)from the experimental AFI-Se and LTA-Se OAS and show that the 3.0-3.3 eV absorption of Se_(12)is enhanced compared to that of Se8.This absorption is responsible for the observed resonant Raman effect of Se_(12)at the 514.5 nm wavelength excitation.Both LTA-confmed Se8 and Se_(12)display rather high thermal stability.
查看更多>>摘要：NiOx/SiO2-Al2O3 catalysts with different pore structures(BET specific surface area: 303-709 m~2 g~(-1),average pore size: 2.2-5.1 nm),acid properties(total amount of acid sites: 0.99-1.66 mmol g~(-1)),and NiO particle sizes(4.6-14.7 nm)were prepared,and the structural factors influencing their catalytic activity for ethylene oligomerization were studied.SiO2-Al2O3 support was prepared by means of a homogeneous precipitation method,and supports with different physicochemical properties were obtained by changing the preparation conditions.Ni was loaded by means of an impregnation method.Catalytic reactions were performed in a fixed-bed down-flow reactor operated at 300 ℃ and 0.1 MPa.NiOx/SiO2-Al2O3 catalysts prepared with the homogenous precipitation method had a higher surface area,more uniform pore size,and a larger amount of acid sites,and they showed a higher activity not only compared with NiOx/SiO2-Al2O3 catalysts prepared by means of our previous coprecipitation method but also compared with Ni-A1SBA-15,the best heterogenous catalyst for ethylene oligomerization reported to data.The catalytic activities of the NiOx/SiO2-Al2O3 catalysts strongly depended on the BET specific surface area and the amounts of acid sites.The optimal amounts of weak,medium-strength,strong,and total acid sites were 0.5,0.3,0.4,and 1.2 mmol g~(-1),respectively.Examination of the structure-activity relationships of the catalysts suggested that their catalytic activity was promoted by close contact between the Ni and acid sites.
查看更多>>摘要：Various amine-impregnated mesoporous silica adsorbents were prepared for a comparative study of 400 ppm CO2 adsorption at room temperature(25 or 30 ℃)under dry and 60% relative humidity conditions.Five types of amines-polyethylenimine(PEI),tetraethylenepentamine(TEPA),triethylenetetramine(TETA),diethylenetri-amine(DETA),and ethylenediamine(EDA)-and three types of mesoporous silica with different pore structures(SBA-15,MCM-41,and MCM-48)were used.The amine loading amount was also optimized according to the CO2 adsorption results obtained using a thermogravimetric analyzer under dry conditions.SBA-15 samples with 50-60 wt% loadings of TEPA and TETA showed a relatively high adsorption capacity of approximately 2 mmol g~(-1).The adsorption capacities of EDA and DETA loaded samples were less than 0.5 mmol g~(-1).The PEI impregnated SBA-15 exhibited relatively high CO2 adsorption rate(0.058 mmol g~(-1)min~(-1)).X-ray diffraction,Fourier transform infrared spectroscopy,N2 adsorption/desorption,and scanning electron microscopy revealed that the amines filled the mesopores of the sample.The amines also covered the outer surface of the mesoporous silica with narrow pore sizes(MCM-41 and MCM48).In humid conditions,SBA-15 with 50 wt% loading of PEI,TEPA,and TETA showed an adsorption capacity of 2.16 mmol g~(-1),2.12 mmol g~(-1),and 1.80 mmol g~(-1),respectively.An enhanced capacity was observed under humid conditions,especially for the PEI-loaded samples.During the cyclic adsorption test,PEI-and TEPA-impregnated SBA-15 exhibited superior cycling stability compared to the sample with TETA,where the material retained a capacity of approximately 2 mmol g~(-1)over 10 cycles.
查看更多>>摘要：H-SSZ-13 and H-SAPO-34 are chabazite(CHA)zeolites and successful methanol-to-olefins(MTO)catalysts.In order to understand their intrinsic origin of catalytic activity and compare their properties,the electronic structure of H-SSZ-13 and H-SAPO-34 referencing to neutral SiO2-CHA and A1PO4-CHA was studied in this work exhaustively.Based on the results,the following conclusions can be made.(1)The catalytic activity of acidic zeolites stems from that the electronic distribution of the valence band maximum(VBM)is highly localized in the acid catalytic center.(2)The acidity of H-SAPO-34 is weaker than that of H-SSZ-13 because the strength of H-0 bond in H-SAPO-34 is stronger than that in H-SSZ-13.@From the Bader Charge analysis,the acidic center of H-SAPO-34 possesses stronger polarization ability than peripheral framework,while in H-SSZ-13 the polarization ability of the acidic center is almost equal with the outer framework.Thus,small gas molecules are easy to reach active centers and so H-SAPO-34 are more efficient for MTO process.
查看更多>>摘要：The development of TiO2-based composites with a broad light response and outstanding photocatalytic performance is very important for the removal of antibiotics.In this work,we prepared a series of new porous graphene(PG)/TiO2 nanocomposites formed the different highly reactive interface within confined space via a partial combustion strategy using TiCl4 as the Ti source.The as-prepared PG/TiO2 exhibited the simultaneous effect of incredible adsorptivity and photodegradation performance toward tetracycline(TC)antibiotic under UV and visible light in contrast to conventional PG/TiO2,pure TiO2(P25)and PG.Optimization experiments showed that PG/TiO2-4% had the optimal removal performance among all the nanocomposites.The removal rate of TC reached up to 95.5%,which was 15% higher than that of I-PG/TiO2 and 25% higher than that of P25 within 90 min.The results were credited to(1)the high specific surface area and porous structure of PG,(2)the broad light response range and rapid separation of h~+ and e~-of PG/TiO2,and@the highly reactive interface between PG and TiO2 nanoparticles.In addition,active radical trapping experiments indicated that·O_2~-was crucial to the elimination of TC.This work showed the new potential of PG/TiO2 nanocomposites for the enhanced photocatalytic performance.
查看更多>>摘要：A series of heteroatom doped ordered mesoporous carbons(HOMCs)such as ordered mesoporous carbon(OMC),nitrogen doped ordered mesoporous carbons(NOMC),phosphorus doped ordered mesoporous carbons(POMCs),and nitrogen and phosphorus co-doped ordered mesoporous carbon(NPOMC)were synthesized via a chemical vapor deposition nanocasting(CVD nanocasting)route using SBA-15 as the template at 800 ℃ for high-performance supercapacitor.The formation of the template and HOMCs were confirmed by various physicochemical characterization techniques such as XRD,RAMAN,BET,SEM-EDAX,HR-TEM and XPS.The magnetic properties of prepared HOMCs were measured.Also,the electrochemical properties of HOMCs were evaluated using electrochemical analyses such as CV,EIS and GCD in 1 M H2SO4 medium.Among the various prepared HOMCs,sample NPOMC showed a high specific capacitance of 355 Fg~(-1)at a current density of 0.5 Ag~(-1)due to the heteroatoms.Moreover,the symmetric device fabricated using NPOMC exhibited 98% columbic efficiency with 98% capacitance retention after 1000 cycles at 2 Ag~(-1)current density.
查看更多>>摘要：~(13)C pulsed field gradient(PFG)NMR was used to quantify self-diffusion of a p-xylene/o-xylene mixture inside zeolitic imidazolate framework-71(ZIF-71)crystals dispersed in a Torlon polymer to form a ZIF-71/Torlon mixed-matrix membrane(MMM).The corresponding reference PFG NMR measurements with a bed of a loosely packed bed of ZIF-71 crystals were also performed.This study is motivated by a demonstrated potential of ZIF-based MMMs for liquid separations.Selective ~(13)C isotopic labelling of each xylene isomer was used to ensure that the self-diffusivity of each isomer in the mixture is measured independently and correctly.The diffusion measurements were performed at different diffusion times at 296 K.The observed dependencies of intra-ZIF self-diffusivities in ZIF-71/Torlon MMMs and the corresponding ZIF-71 crystal beds on diffusion time were explained by an influence of the external crystal surface on the studied diffusion process.Analysis of the time dependencies of the self-diffusivities measured for each xylene isomer allowed obtaining intra-ZIF self-diffusivities not perturbed by crystal surface effects as well as the corresponding diffusion selectivity for the studied sorbate mixture.The reported selectivity of around 4 demonstrates promising separation behavior of the considered membrane type.
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