The layer-by-layer (LbL) assembled multilayer has been widely used as good barrier film or capsule due to the advantages of its flexible tailoring of film permeability and compactness. Although many specific systems have been proposed for film design, developing a versatile strategy to control film compactness remains a challenge. We introduced the simple mechanical energy of a high gravity field to the LbL assembly process to tailor the multilayer permeability through adjusting film compactness. By taking poly(diallyldimethylammonium chloride) (PDDA) and poly{1–4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAzo) as a model system, we investigated the LbL assembly process under a high gravity field. The results showed that the high gravity field introduced effectively accelerated the multilayer deposition process by 20-fold compared with conventional dipping assembly; the adsorption rate was positively dependent on the rotating speed of the high gravity equipment and the concentration of the building block solutions. More interestingly, the film compactness of the PDDA/PAzo multilayer prepared under the high gravity field increased remarkably with the growing rotational speed of the high gravity equipment, as demonstrated through comparisons of surface morphology, cyclic voltammetry curves, and photoisomerization kinetics of PDDA/PAzo multilayers fabricated through the conventional dipping method and through LbL assembly under a high gravity field, respectively. In this way, we have introduced a simple and versatile external form of mechanical energy into the LbL assembling process to improve film compactness, which should be useful for further applications in controlled ion permeability, anticorrosion, and drug loading.Keywords: acceleration of diffusion process; high gravity field; improvement of film compactness; layer-by-layer assembly; photoisomerization of Azo group; reduction of ion permeability;

CdTe-based quantum dots (QDs) with high photoluminescence quantum yields (PL QYs) were synthesized in a short time (less than 45 minutes). Mercaptosuccinic acid (MSA) was employed as a stabilizer and N2H4 as a growth promoter to accelerate the growth of CdTe and CdSexTe1−x QDs. Red-emitting CdTe QDs with a PL QY of 25% were obtained and the highest PL QY reached 55%. CdSexTe1−x QDs with emission peak positions of 518 nm to 750 nm were obtained. The rapid growth of QDs depends on the interaction between MSA and Cd2+, and N2H4 plays a key role in accelerating the growth to a certain level. Thus, the QD particle size can be controlled by manipulating N2H4 concentration in solution. A low N2H4 concentration seems feasible to obtain high-quality QDs.

•A rotor–stator reactor (RSR) was used for nano-support preparation.•CeO2 nano-support was prepared by microemulsion-gas method in the RSR.•The CeO2 nano-support had a narrow size distribution and a high specific surface area.•Au/CeO2 catalyst was prepared by using the CeO2 nano-support.•Full CO conversion was achieved at 115 °C by using the Au/CeO2 catalyst.CeO2 nano-support was prepared by the reaction of water-in-oil microemulsion with NH3 gas in a rotor–stator reactor (RSR). The influences of different parameters including reaction temperature, rotation speed and final pH of the suspension on the properties of the CeO2 nano-support were investigated by BET and XRD. CeO2 nano-support with a diameter of about 5 nm, size distribution of 4–6 nm and specific surface area of 104 m2/g was obtained under the optimum operating conditions of reaction temperature of 40 °C, rotation speed of 800 rpm and final pH of the suspension of 11 and was deposited with Au for CO oxidation reaction. The results demonstrated that CeO2 nano-support prepared by the microemulsion-gas method in the RSR had a small particle size and narrow size distribution and showed high catalytic activity after it was deposited with Au. Full CO conversion was achieved at 115 °C by using the as-prepared Au/CeO2 catalyst.

In this study, simulated coking wastewater was treated by the O3/Fenton process in a rotating packed bed (RPB) and the results were compared with those by the O3 process. Contrast experiments indicated that the degradation rates of phenol, aniline, quinoline and NH3–N in the wastewater reached 100%, 100%, 95.68% and 100% respectively under the optimum operating conditions in the O3/Fenton process and were much higher than those in the O3 process. The BOD5/COD value of the simulated coking wastewater treated in the O3/Fenton process reached 0.46 and was 135% higher than that in the O3 process. The degradation pathways of phenol, aniline, quinoline and NH3–N in the simulated coking wastewater were also discussed. The results indicated that a combination of the advanced oxidation processes and the RPB can enhance the treatment efficiency of coking wastewater.

This study was conducted to investigate the effect of inorganic salts on the mass-transfer coefficient of O3 and decolorization of azo dye (Acid Red 14, AR14) solution through ozonation in a microporous tube-in-tube microchannel reactor (MTMCR). The overall volumetric mass-transfer coefficient (KGa) of O3 in the MTMCR was deduced by material balance. The effects of different salts on the KGa of O3 and decolorization efficiency of the AR14 solution were studied, and results show that both were significantly affected by the inorganic salts. Although the KGa of O3 and the decolorization efficiency of AR14 increased with increasing salt concentration and pH, the effect of NaNO3 was much weaker than that of NaCl, Na2SO4, Na2CO3, and NaHCO3. The enhanced KGa of O3 and decolorization could be due to the generation of species with high oxidizing ability in the presence of the salts.

The effects of erythorbic acid (EA) and ethanol on the aqueous formation of cadmium telluride (CdTe) quantum dots (QDs) were explored in this work. Without N2 protection, CdTe QDs were synthesized with cadmium chloride and sodium hydrogen telluride as the Cd source and Te source, respectively, together with EA and with 3-mercaptopropionic acid (MPA) as the co-passivating ligand. The experimental results indicated that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdTe QDs with reasonably good optical properties. Including ethanol during the synthesis improved the photoluminescence intensity. To attain good optical properties, it is also important to tune experimental parameters such as pH, temperature, reaction time, molar ratio of MPA/Cd, and sodium borohydride dosage. The very reason that EA promoted formation of CdTe QDs is because of its reducibility and passivation on the QD surface. The present study suggests that the use of EA and ethanol could be a practical means to promote the photoluminescence of CdTe.

•Erythorbic acid (EA) was employed in aqueous synthesis of CdS quantum dots (QDs).•EA acted as an oxygen scavenger and passivating ligand in the synthesis.•EA enhanced the optical properties of CdS QDs and the mechanism was discussed.•This route offers an easy and green pathway for producing QDs with good dispersion.The effect of erythorbic acid (EA) on the aqueous formation of CdS quantum dots (QDs) at room temperature was explored in this work. Without N2 protection, CdS QDs were synthesized in water by a one-pot non-hot-injection approach at room temperature. The Cd and S sources were CdCl2 and Na2S, respectively, together with 3-mercapto-propionic acid (MPA) as the passivating ligand. The experimental results indicate that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdS QDs with reasonably good optical properties, and it is also important to tune experimental parameters such as MPA-to-Cd molar ratios, pH, and reactant concentrations. The mechanism about the EA promoted formation of CdS QDs was discussed in terms of NMR, IR, in situ absorption, and photoemission studies. The very reason for the EA promoted formation of CdS QDs is due to its reducibility and passivation on the QD surface (particularly in alkaline environment). The present study suggests that the use of EA could be a practical means to enable the room-temperature formation of QDs in water.

The treatment of acidic phenolic wastewater by ferrous-catalyzed ozonation (O3/Fe(II)) process in a rotating packed bed (RPB) was studied, and the O3/Fe(II) process was compared with the O3 process. It was observed that the phenol degradation rate in the O3/Fe(II) process was roughly 10% higher than that of O3 process in acidic environment in the RPB. It is also found that the degradation efficiency of phenol was significantly affected by the rotation speed and inlet ozone concentration. Phenol degradation efficiency increased with increasing initial pH of the phenolic solution, rotation speed, and concentrations of the inlet ozone gas, as well as a decreasing liquid flow rate and initial concentrations of phenol. Phenol degradation efficiency reached maximum at a temperature of 25 °C and an initial Fe(II) concentration of 0.4 mM. The result of the contrast experiment showed that the biological oxygen demand/chemical oxygen demand (BOD/COD) of the phenol solution increased from 0.2 to 0.59 after the solution was treated by O3/Fe(II) process. The intermediates of the ferrous-catalyzed ozonation process were identified by gas chromatography/mass spectroscopy (GC/MS), and it is deduced that the pathway of phenol degradation in ferrous-catalyzed ozonation is different from that in ozonation. Hydroquinone and 1,4-benzoquinone were the main intermediates, and a small amount of polymeric intermediates was found in the O3/Fe(II) process.

An approach to fabricate Cu@SiO2 nanostructured materials was presented by using Cu nanoparticles (NPs) produced in a tube-in-tube microchannel reactor (TMR) as the core. Due to the excellent micromixing efficiency of the TMR, monodisperse Cu NPs of sub-5 nm were easily obtained. A combination of the direct silica-coating technique with the remarkable ability of the TMR for mass production of nanoparticles may open an economic pathway for producing core-shell nanomaterials.

This article presents the modeling and experimental investigation of the simultaneous absorption of CO2 and NH3 into water in a rotating packed bed (RPB). A model was established to predict the overall volumetric mass-transfer coefficients (KGa) of CO2 and NH3 with reactions in the RPB at gravity levels of about 70−250g. Experiments involving the simultaneous absorption of CO2 and NH3 into water in an RPB were carried out under different conditions, and it was found that KGa increased with increasing rotation speed, liquid volumetric flow rate, gas volumetric flow rate, and NH3/CO2 molar ratio. It was observed that the model was in good agreement with the experimental data, with deviations within 10% compared to the experimental values.

The relatively low gas–liquid mass transfer efficiency and the low activity of ozone in acidic solution limit the application of ozonation. In this work, ferrous-catalyzed homogeneous ozonation (FCHO) was adopted to treat acidic phenol wastewater in a rotating packed bed (RPB), and the operating conditions in this process were optimized by using a response surface method (RSM). The variables investigated included the rotation speed (300–1500 rpm), liquid flow rate (10–30 L/h), ferrous ion concentration (0–0.8 mM) and inlet ozone concentration (30–70 mg/L). Experiments were carried out on the basis of a central composite design approach. It was found that ferrous ion could effectively enhance the ozonation of phenol and the rotation speed affected both phenol degradation degree and ozonation efficiency greatly. Quadratic models were developed with phenol degradation degree and ozonation efficiency as the responses, and the model predictions were confirmed to fit well with the experimental data with a deviation less than 11%. The BOD/COD values increased from 0.2 to 0.56 at the maximum phenol removal rate in the validation experiment. It is concluded that the quadratic model is an effective tool to optimize the FCHO process of phenol in the RPB.Highlights► Fe(II) as the catalyst to improve ozonation efficiency of phenol. ► A rotating packed bed as the liquid–gas contactor. ► A response surface method (RSM) was used to optimize ozone concentration. ► Model predictions fit well with the experimental data with a deviation less than 11%. ► A phenol removal rate of 70% and a BOD/COD value of 0.56 was reached.