A new solvent sublation (SS) system for chiral separation is introduced by using phenylsuccinic acid (H2A) as the model enantiomers. The experiments were carried out in a traditional SS apparatus but with collaborative chiral selectors: dibenzoyl-L-tartaric acid (L-DBTA) in the organic phase and hydroxypropyl-β-cyclodextrin (HP-β-CD) in the aqueous phase. The chiral recognition abilities of the two selectors are opposite for the H2A enantiomers. Several important parameters were investigated. The results demonstrate that enantioselective sublation and partitioning behavior are mainly dependent on the pH of the solution, the concentrations of chiral selectors and H2A. Furthermore, the flow rate of air and flotation time also have some effects on the enantioseparation. Under the optimized conditions, the enantioselectivity expressed by the separation factor (β) and enantiomer excess (e.e.%) are 2.47 and 29.50%, and the yields of R-H2A and S-H2A are 0.23 and 0.13 g·L−1, respectively. Compared with the SS system with the single selector HP-β-CD in the aqueous phase (or L-DBTA in the organic phase), the increased values of β and e.e.% in the new SS system with collaborative selectors are 1.31 (or 1.38) and 5.90% (or 13.82%), respectively.

A series of multi-walled carbon nanotubes (MWCNTs)-loaded Bi2S3 nanomaterials composites (MWCNTs/Bi2S3) were prepared by hydrothermal method. The crystallization, morphology and other properties of the obtained MWCNTs/Bi2S3 composites were completely characterized by powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FT-IR), Thermal gravimetric analysis and differential thermal analysis (DTA-TG), N2 adsorption-desorption isotherm, and UV–vis diffuse reflectance spectroscopy (DRS). In this work, the photocatalytic activity of the as-prepared materials was evaluated for methylene blue (MB) degradation under visible light irradiation. Comparing with others work, the composites showed excellent photocatalytic performance and maintained a good stability during the constant cycling experiment. Finally, a possible photocatalytic reaction mechanism on the MWCNTs/Bi2S3 composites was proposed.

A new composite catalyst was constructed by immobilizing active site N,N-dihydroxypyromellitimide (NDHPI) on the co-catalyst Co-doped mesoporous sieve SBA-15 through the chemical bond with the 3-(glycidoxypropyl) trimethoxysilicane used as the silylation agent. The catalyst was characterized by various means. The new catalyst showed significantly higher activity in toluene aerobic oxidation at 90 °C with acetonitrile as a solvent or under solvent-free condition compared with the NDHPI and co-catalyst independent system. The effects of the reaction conditions such as temperature, oxygen pressure, catalyst amount on the toluene oxidation over the immobilized catalyst were also investigated. After reuse for three times, the composite catalyst kept the activity without loss of Co from SBA-15.A new composite catalyst was constructed by immobilizing active site N,N-dihydroxypyromellitimide (NDHPI) on the co-catalyst Co-doped mesoporous sieve SBA-15 through the chemical bond with the 3-(glycidoxypropyl) trimethoxysilicane used as the silylation agent. The catalyst was characterized by various means. The catalytic performance of the composite was evaluated in toluene aerobic oxidation and the reuseability of the catalyst was also investigated.

The assembly of layered double hydroxides (LDHs) and multi-walled carbon nanotubes (MWCNTs) nanohybrids was prepared as MWCNTs/LDHs by co-precipitation. The synthesized nanoparticles were characterized by using XRD, FT-IR, SEM/EDX, TGA and BET. XRD and SEM studies proved that MWCNTs phases did not enter into the interlayers of LDHs, they dispersed over the LDHs surface homogeneously. BET results showed that MWCNTs/LDHs possessed hierarchically porous nanostructure with large surface area (124.974 m2/g) and great pore volume (0.604 cm3/g). Batch experiments were conducted to study the adsorption efficiency of Congo red (CR). It was worthy to note that MWCNTs/LDHs exhibited excellent adsorption performance with the maximum CR adsorption capacity of 595.8 mg/g in weak acidic environment. The adsorption kinetics and isotherm parameters can be well described by the pseudo-second-order and the Langmuir isotherm models, respectively. The thermodynamic studies indicated that the adsorption process was spontaneous and endothermic.

•Cu2O/ZnAl-CLDH composite has been prepared by a facile method.•The Cu2O/ZnAl-CLDH photocatalysts improve the utilization of visible light.•The Cu2O/ZnAl-CLDH catalysts exhibit better photocatalytic activity and stability for the photodegradation of Methyl Orange (MO).The Cu2O/ZnAl calcined layered double hydroxides (Cu2O/ZnAl-CLDH) composites had been successfully synthesized by a facile method. The prepared photocatalysts were characterized by X-ray diffraction, Scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectra to show the structure of the as-synthesized materials. The results revealed that the Cu2O nanoparticles were evenly distributed on the surface or the internal frame of ZnAl-CLDH to form the heterostructure of ZnO-Cu2O. The photocatalytic performance of Cu2O/ZnAl-CLDH was evaluated by the photodegradation of Methyl Orange (MO) under visible light irradiation. The effects of the Cu/CLDH molar ratio, calcination temperature and MO concentration were investigated. The photocatalyst shows a high photocatalytic activity (90.18%) at the optimum of Cu/CLDH molar ratio of 1:1, calcination temperature of 500 °C and initial MO concentration of 20 mg/L. In addition, after three cycles the removal efficiency of MO is still higher than 80% for reused Cu2O/ZnAl-CLDH, demonstrating its great potential application in the field of photocatalysis. From the experimental results, a possible photocatalytic mechanism of the Cu2O/ZnAl-CLDH composite was proposed.

Adsorption of 2, 4, 6-trichlorophenol (TCP) onto the calcined Mg/Al-CO3 layered double hydroxide (CLDH) was investigated. The prepared Mg/Al-CO3 layered double hydroxide (LDH) and CLDH were characterized by powder X-ray diffraction (XRD) and thermo gravimetric analyzer-differential scanning calorimeters (TG-DSC). Moreover, 2,4,6-trichlorophenol (TCP) was removed effectively (94.7% of removal percentage in 9 h) under the optimized experimental conditions. The adsorption kinetics data fitted the pseudo-second-order model well. The Freundlich, Langmuir, and Tempkin adsorption models were applied to the experimental equilibrium adsorption data at different temperatures of solution. The adsorption data fitted the Freundlieh adsorption isotherm with good values of the correlation coefficient. A mechanism of the adsorption process is proposed according to the intraparticle diffusion model, which indicates that the overall rate of adsorption can be described as three steps.

High-purity NiCo2S4 mesoporous nanosheets prepared through utilizing CS2 as novel sulfur source were fabricated as advanced electrode for electrochemical supercapacitors. Well-defined X-ray diffraction pattern, high specific surface areas and suitable pore size distribution (2∼6 nm) were observed for the as-obtained NiCo2S4 sample, demonstrating remarkable electrochemical performances resulting from the porous feature of NiCo2S4 nanosheets that increase the amount of electroactive sites and facilitate the electrolyte penetration. The as-assembled asymmetric supercapacitor (ASC) exhibits a high energy density of 25.5 Wh kg−1 at a power density of 334 W kg−1 and still remains an impressive energy density of 10.8 Wh kg−1 at a high power density of 8 kW kg−1. The outstanding performance of this ASC device will undoubtedly make the mesoporous NiCo2S4 nanosheets attractive for high-performance electrode materials.

In the study herein we focused on enantioseparation of phenylsuccinic acid (PSA) enantiomers using an aqueous two-phase system (ATPS) composed of ethanol and ammonium sulfate. Based on phase-forming points and salting-out points, a modified phase diagram of ethanol/ammonium sulfate system with three distinct phase areas, including homogeneous area, ATPS area and salting-out area, has been constructed experimentally. The ATPS optimization and evaluation of chiral separation efficiency for PSA enantiomers have been investigated thoroughly. A hydrophilic chiral selector, hydroxypropyl-β-cyclodextrin (HP-β-CD), which has good chiral recognition ability for R-PSA, was added into bottom phase. The chiral separation efficiencies, namely distribution coefficients and separation factor, were affected by various process variables, including phase compositions of ATPS, concentrations of HP-β-CD and PSA enantiomers, pH value and operational temperature. Under the optimum conditions, separation factor could reach 1.42 after just one step extraction. This environmentally benign chiral separation technique opens up new possibilities for preparative separation of other racemic compounds at a large-scale.

Aqueous two-phase flotation (ATPF) is especially applicable to bioseparation. However, there is no previous work reporting on its application in enantioseparation. Using phenylsuccinic acid (H2A) as the model enantiomers, ATPF was first introduced into the field of chiral separation. The contributions of a series of ATPF systems to the enantioseparation were investigated. The results indicated that an appropriate increase in the amount of phase-forming components and a decrease in pH values (from 5.5 to 2) are both beneficial for the enantioseparation. Enantioselective flotation and partitioning behavior are mainly dependent on pH values of the solutions, types, and concentrations of chiral selectors. Furthermore, salt, PEG, flow rates of air, and flotation time also have some effects on the enantioseparation. Under the optimal conditions, the enantioselectivity was calculated in terms of the separation factor (α) and enantiomer excess (e.e. %) as 1.99 and 23.49 %, respectively. Finally, the most reasonable mechanisms for H2A enantioseparation in ATPF system have been proposed. An ATPF system composed of PEG2000/(NH4)2SO4 was proved to have the best ability for the separation of H2A enantiomers. The explorations in our study will further enrich the enantioseparation methods and pave the way for the application of ATPF in the enantioseparation field.

•Intercalated NAA into the Mg/Al–NO3–LDH by ion-exchange method.•Thin films were made by the LBL method with polymers and Mg/Al–NAA–LDH.•The films were put into various solutions, and discuss the release mechanism.•The mechanism accorded with first-order kinetics.An active agent a-naphthaleneacetate (NAA), a plant growth regulator was intercalated into the layered double hydroxides Mg/Al–LDH by ion-exchange method. And we prepared the films by the method of layer-by-layer self-assembly with Cationic Polyacrylamide, Polyacrylic acid sodium and LDH. The obtained compounds were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) and Scanning Electron Microscopy (SEM) techniques. The XRD datas demonstrated the guest size and the orientation of anions between the layers was determined. After intercalation, it was proposed that the NAA anions were accommodated in the interlayer region as a bilayer of species with the carboxyl attaching to the upper and lower layers. The FT-IR of the powder from film shows that Mg/Al–NAA–LDH was absorbed on the quartz glass. The film was putted into various solutions, and the release of NAA from the film showed obvious release effect. The release mechanism may be based on the dissolution and ion-exchange process according to first-order kinetics.The data obtained from the NAA released into the aqueous solution at different temperature and pH solutions fitted to the first-order kinetic. The kinetic indicated that the release process was controlled by the course of dissolution and ion-exchange process.Download high-res image (69KB)Download full-size image

ZnO/Al2O3/Bi2O3 mixed-metal oxide (ZnAlBi-MMO) has been successfully prepared by the coprecipitation method and controllable calcination. Powder X-ray diffraction, high-resolution transmission electron microscopy and UV–Vis diffuse reflectance spectra confirmed the structure of as-synthesized solids. The results reveal that the synthetic methods can provide the heterostructure of MMO. The photocatalytic activity of ZnAlBi-MMO was evaluated by the photodegradation of methylene blue (MB) under visible light irradiation. Factors that may affect the photodegradation behavior were studied such as calcination temperature, catalyst dose and pH. Furthermore, the stability of synthesized photocatalysts was investigated by studying the photocatalytic ability of reclaimed ZnAlBi-MMO. The results showed the removal efficiency of MB was higher than 83 % even after four successive photoreactions, demonstrating the great potential of layered double hydroxides as catalyst supports. The possible mechanism underlying the enhanced photocatalytic activity of Bi2O3 was also discussed.

A monolithic molecularly imprinted polymer (monolithic MIP) for dibenzoyl-D-tartaric acid (D-DBTA) was prepared in a stainless-steel chromatographic column tube (50 mm × 4.6 mm I.D.) as HPLC stationary phase through in situ polymerization. By optimizing polymeric and chromatographic conditions, the chiral separation of DBTA enantiomers was successfully achieved in the obtained MIP in less than 25 min with a resolution Rs = 1.25, whereas no enantioseparation effect was found on the monolithic non-imprinted polymer (NIP). Thermodynamic data of the enantioseparation were calculated. The results revealed that two different thermodynamic processes existed within the temperature range investigated, moreover, just at the transition temperature (50 °C) of the two processes, separation factor α reached its maximum. Scathcard analysis indicated that only one class of binding sites existed in the obtained MIP, with its Kd and Qmax estimated to be 5.457 × 10−4 mol L−1 and 229.6 μmol g−1, respectively. Nitrogen adsorption experiment proved that the prepared MIP had a large specific surface area of 105 m2 g−1. Scanning electron microscopy showed that large flow-through pores were present in the prepared monolith. As a consequence, the column backpressure was only 1.2 MPa with acetonitrile as mobile phase at a flow rate of 1.0 mL min−1.

Herein we focused on using a novel separation technology, solvent sublation, for the enantioseparation of α-cyclohexylmandelic acid (CHMA). The experiment was carried out in a conventional bubble column using d-iso-butyl tartrate (d-IBTA) and sodium dodecyl sulfate (SDS) as a chiral selector and surfactant, respectively (Fig. 7). Several important parameters influencing the separation performance, such as the type of organic phase, the pH in the aqueous phase, and the concentrations of CHMA, d-IBTA, and SDS were investigated. Under the optimal operating conditions, the enantiomeric excess and separation factor were 54.85% and 4.5, respectively. The yields of d-enantiomer and l-enantiomer were 82.20% and 38.94%, respectively. Finally, the thermodynamic properties of the separation were investigated, which indicated an enthalpy-controlled process. This technique is an efficient chiral separation method, with many advantages, such as low amounts of organic solvent and chiral selector required and easier realization of the multi-stage operation.