查看更多>>摘要：Hierarchical Beta zeolite (named ECNU-41) was directly synthesized with commercially available ionic liquid 1-butyl-1-methylpyrrolidinium hydroxide as organic structure-directing agent (OSDA) in the absence of any surfactants or polymers. The ECNU-41 crystals were composed of nanorods through a unique stacking manner, exhibiting a morphology resembling the Chinese traditional toy "burr puzzle". The orderly crisscrossed stacking ECNU-41 possesses high hydrothermal stability, abundant intercrystal mesoporosity, and enriched phase of polymorph B. In comparison to conventional nanosized Beta zeolites, ECNU-41 aluminosilicate and titanosilicate exhibited more remarkable and competitive catalytic performances in a variety of reactions, including benzene alkylation, methanol to propylene, and alkenes epoxidation. With improved diffusion rate and mass transfer due to the hierarchical structure, ECNU-41 is expected to serve as promising catalysts for those reactions involving bulky molecules.
查看更多>>摘要：The electrospinning method combined with high temperature thermal annealing was used to prepare TiO2 fibers modified with different concentrations of Co3O4. Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), desktop scanning electron microscope (TM3030)-energy spectrometer (SwiftED3000), thermal analyzer (TGA), X-ray diffractometer (XRD), X-ray photoelectron energy Spectral analyzer (XPS), Brunauer-Emmett-Teller (BET) (BET) were used to study the influence of different cobalt oxide concentrations on the morphology of mesoporous TiO2 fibers. Cyclic voltammetry (CV), linear sweep voltam-metry (LSV), electrochemical impedance spectroscopy (EIS) and continuous cycle method were used to evaluate the fiber's oxygen evolution reaction (OER) and oxygen reduction (ORR) reactivity. It was found that the fiber with a molar ratio of Co to Ti of 1:10 showed the best performance for both OER and ORR reactions in alkaline solution. The fiber showed an overpotential of 382 mV at a current density of 10 mA cm~(-2), a Tafel slope of 58 mV·dec~(-1), and a half-wave potential change of only 10 mV after 4000 CV cycles. It has an onset potential of 0.83 V (vs RHE) in the ORR reaction. The OER/ORR overpotential gap (E) of 0.85 V is significantly lower than commercial platinum/carbon and bulk TiO2 analogs. Obviously, this catalytic activity stems from the synergy between C03O4 and TiO2 fibers. In addition, the higher specific surface area and the presence of disordered mesopores provide a higher charge carrier density during the electrocatalytic process, which improves the reaction activity.
查看更多>>摘要：Preparation of high specific surface area activated carbon from rice husk for the removal of ofloxacin from medical wastewater. The optimum conditions for the preparation of activated carbon were a nitrogen doping ratio of 1:1:4 and an activation temperature of 800 °C (AC). The samples were characterised by N2 adsorption isotherms, BET, FT-IR, TGA, XPS and SEM. The data showed that the specific surface area of AC was up to 1818.20 m~2 g~(-1) with a total pore volume of 1.12 cm~3 g~(-1). AC formed N-containing functional groups on the surface and had good thermal stability. Scientific batch experiment studies were conducted to investigate the effect of pH, initial concentration, temperature and coexisting ions on the ofloxacin adsorption. The qe reached a maximum value of 780 ± 20 mg g~(-1) and maintained a removal efficiency of 51.1% after four regeneration cycles. The adsorption equilibrium data and the adsorption process were well represented by Langmuir model and general-order kinetic model, respectively. Thermodynamic studies of adsorption had shown that the adsorption process was autogenous and endothermic. Possible adsorption mechanisms for this material were also analysed. Finally, treatment of synthetic medical wastewater with AC resulted in a high removal rate of 98.3%. The superior adsorption properties combined with ease of preparation, ease of separation and excellent regeneration properties, make this material potentially effective for the removal ofloxacin from real medical wastewater.
查看更多>>摘要：Bronsted acid of zeolite Y plays an important role in catalytic cracking reaction. However the proportion of strong Bronsted acid in conventional zeolite Y is small which limits the efficiency of transformation. This work described a way to achieve the goal of significant increasing the density of strong Bronsted acid via introducing Zr~(4+) into the framework of zeolite Y. The density of strong Bronsted acidity increased from 0.085 (HY) to 0.208 mmol/g ([Zr,Al]-HY). Systematic characterization results showed that the introduction of Zr~(4+) could produce more Si(1Al) but less Si(3Al) and Si(2Al) species in zeolite which was responsible for the high density of Bronsted acid. And abundant mesopores were also formed during the Zr~(4+) implanting. For the catalytic cracking results of n-octane, the conversion on [Zr,Al]-HY was 1.67 times of that on conventional HY. The apparent activation energy of cracking n-octane on [Zr,Al]-HY was reduced to 73.3%, which indicated that the increase of strong Bronsted acid had significant effect on catalytic cracking. On the other hand, a large number of mesoporous structures of [Zr,Al]-HY provided a good foundation for the catalytic cracking of steric hindered 1.3.5-triisopro-pylbenzene (1,3,5-TIPB).
查看更多>>摘要：Polyester fabric membrane was firstly composited with (NH4)2HPO4 through solvent evaporation method, and then α-zirconium phosphate (a-ZrP) nanoparticles were in situ grown on the membrane via an interfacial growing process. Afterwards, the as-prepared membrane was modified by Octadecyltrichlorosilane (OTS). Morphology and chemical composition of the composited membrane were confirmed by Scanning Electron Microscope (SEM). All the composited membranes exhibited superhydrophobicity when they were modified by OTS, and N_(0.2)ZrP possessed the highest contact angle (CA = 156.3°). The hydrophobicities of the composited membranes were well conserved after treating with acid, alkaline and salinity (all CAs >150°). All the composited membranes exhibited excellent oil/water separation efficiency, while N_(0.2)ZrP demonstrated the highest efficiency of 99.7%, and still remained high efficiency of 99.6% even after 30 cycles of wetting-drying process. This work provided a facile approach for fabricating thermal stable and superhydrophobic composited membrane that lead to high separation efficiency for practical application in oil/water separation.
查看更多>>摘要：Clinoptilolite is a natural zeolite employed in Cs~+ removal, and its cesium form transforms, by heating, into a matrix composed mainly by CsAlSi5O_(12) (CAS) with smaller quantities of glass and CsAlSi2O6 (pollucite). Both crystalline compounds were proposed as host for ~(137)Cs, albeit pollucite is considered superior. This work shows how, by mixing Cs-clinoptilolite and amorphous hydrated aluminum hydroxide (L), it is possible to modify the solid-state transformation of the zeolite and favor the crystallization of pollucite over CAS. Cs-clinoptilolite, L and several mixtures of the two materials were preliminary subjected to thermal and XRD analyses. Muffle treatments of 32 h at 1200 °C and 8 h at 1300 °C, followed by Q-XRD analyses, were performed on some materials. Unlike CAS, pollucite always crystallized. The greater the quantity of L in the mixture, the lower the ratio between the quantities of CAS and pollucite formed. In the range 1200-1300 °C, the CAS/pollucite ratio decreases with temperature. Al2O3-polymorphs (mainly corundum) and glass were ubiquitous in the fired mixtures, whereas mullite was not. By varying the content of L in the mixture, the distribution of cesium among the Cs-bearing phases varied, and for some compositions most of the cesium was trapped inside pollucite.
查看更多>>摘要：Metal ions released through industrial and human activities are difficult to degrade in the environment, and copper (II) ingestion and accumulation in the body would cause harm to human health and even disease. The environmentally friendly materials for simultaneous detection and removal of toxic ions are urgently required to be developed. Herein, carbon dots (CDs) with excellent optical properties as crosslinking agent introduced into chitosan-based membranes with freeze casting technique. The as-synthesized fluorescent membranes (CS-CDs) could generate fluorescent response to copper (II) with adsorption capacity (12.48-49.97 mg/g). Based on the stable fluorescence signal of CS-CDs and fluorescence quenching with copper (II), a simple fluorescence spectrometry method for detection of copper (II) was established. The fluorescence intensity of CS-CD-4 decreased linearly with copper (II) concentrations ranging from 0 to 350 μmol/L. Moreover, the 3D regular honeycomb-like porous structure of CS-CDs facilitated the mass transfer and provided more effective sorption sites. The adsorption isotherm and kinetics were more suitable for the Langmuir model (R = 0.9927) and pseudo-second-order model (R = 0.9989), which indicated the adsorption were monolayer adsorption and chemisorption, respectively. As a result, the CS-CDs with dual-functionalities of detecting and adsorbing copper (II) were successfully fabricated, demonstrating the potential application prospect in environmental protection.
查看更多>>摘要：Biochar with hierarchical pores is one of candidates for Pb(II) removal. In this study, we proposed the Aspergillus tubingensis pretreatment coupling with NaOH activation method to prepare the biochar with micro-mesoporous structure, and the corresponding characteristics and mechanism of Pb(II) adsorption were explored in detail. The result revealed that A. tubingensis mainly decomposed the cellulose in biomass to enhance the activation effect of precursor, which was conducive to create the hierarchical pores and improved the specific surface area (Sbet) of biochar. The microbial pretreatment time was a key factor in the preparation of the ideal biochar, the ACEA-14 sample prepared by A. tubingensis pretreatment of 14 days had the highest S_(BET) of 2786 m~2 g~(-1) and the obvious hierarchical pores, and it also included the order crystal structure and the abundant functional groups. The Pb(II) adsorption experiment indicated that the ACEA-14 sample had prominent the adsorption performance (122.7 mg g~(-1)) under the certain conditions (initial pH of 6.0, adsorbent dosage of 0.4 g L~(-1) and contact time of 8.0 h). This adsorption process was well fitted with pseudo-second order model and Freundlich isotherm model, showing a typical multilayer adsorption The Pb(II) adsorption mechanism of the ACEA-14 sample included the ion exchange, surface complexation, cation-π bond interactions and physical diffusion, and such hierarchical pores were conducive to the Pb(II) transportation, which guaranteed the continuous adsorption. In addition, the regeneration experiment and ternary heavy metal adsorption proved that the ACEA-14 sample had the good application value.
查看更多>>摘要：In this work, mesoporous silica nanoparticles (MSN) hybridized with an organosilane are grafted with hyper-crosslinked poly(vinylbenzyl chloride) (PVBC), which is anchored into the mesopores and onto the external surface of MSN. The obtained nanoparticles are characterized by a MSN-templated hierarchical porosity composed of micropores, mesopores and macropores originated from the hyper-crosslinking of the PVBC phase, with a microporous fraction reaching up to 28% of the total pore volume. Tested for the adsorption of a model dye (Rhodamine 6G, Rh6G), these nanoparticles result much more efficient in Rh6G adsorption with respect to plain MSN, showing a Rh6G uptake of about 125 mg/g in highly concentrated solutions (1000 mg/L) and quite complete removal (about 98%) of the dye in more diluted conditions (30 mg/L) with comparable efficiency in repeated adsorption cycles. Overall results demonstrate the key role of the hierarchical porosity of the hyper-crosslinked PVBC-grafted MSN to tailor their adsorption properties.
查看更多>>摘要：Realizing the controllable adjustment on textural and acid properties of silicoaluminophosphates (SAPOs) is crucial for obtaining excellent-performance catalyst via acid-etching method. However, there are difficulties due to the lack of understanding of the mechanism of selective desilication for acid etching. In this paper, parent SAPO-34 were exposed to a series citric acid solutions aimed to investigate the influence of acid concentration on the physicochemical properties of the resulted SAPO-34 and elucidate the mechanism of selective desilication. The results showed that citric acid concentration plays a decisive role in efficiently manufacturing hierarchical pore structure and selectively extracting specific Si species. The diverse acid resistance of Si-O-Si and Si-O-Al bonds near or in different Si species (Si islands and isolated Si(4Al)) is responsible for the selective desilication of citric acid. The coupling effects of the differential distribution of Si species in parent SAPO-34 and the selective desilication influence the generation of the secondary pore and the strength and amount of acid sites of the resulted SAPO-34. Compared to the parent SAPO-34, the acid-treated SAPO-34 exhibited a longer lifetime and a higher selectivity for light olefins (ethylene and propylene) when used in methanol-to-olefins (MTO) reaction.
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