Temperature Of Reaction System Research Articles

CFD Simulation of Thermal Runaway Scenario in Styrene Polymerization Reaction

Polymerization reaction is a strong exothermic reaction that is prone to thermal runaway accidents. To prevent thermal runaway accidents, a styrene thermal polymerization reaction model is established by using computational fluid dynamics (CFD). The failure of stirring speed, cooling temperature of cooling jacket and cooling flow rate during the reaction process are simulated to explore the impact of runaway scenarios on reaction temperature rise and hot spot distribution. The results show that under the conditions of stirring speed of 160 r/min, cooling temperature of 155 ℃ and cooling flow rate of 3.2 m/s, the average temperature of the reaction system is lower and there are fewer hot spot areas, which reduces the possibility of thermal runaway accidents. The monitoring point position that best represents the average temperature of the entire reaction system is located at or above the top one-third of the liquid level.

Noble metal-free Mn0.2Cd0.8S/NiSe2 nanocomposites for efficient photothermal-assisted photocatalytic H2 evolution

Photothermal-assisted photocatalytic H2 evolution has attracted increasing attention in solar energy-hydrogen energy conversion. Herein, a novel Mn0.2Cd0.8S/NiSe2 (MCS/NiSe2) nanocomposite heterojunction with photothermal and co-catalyst dual effects was constructed to boost visible-near-infrared (Vis-NIR) light-driven H2 evolution activity. MCS/NiSe2 nanocomposite could obtain increased light absorption intensity, affluent active reaction sites and enhanced charge separation efficiency because of the decoration of NiSe2 co-catalyst. Meanwhile, the photothermal effect of NiSe2 could raise reaction system temperature, thus further accelerating carriers transfer and surface reaction rate. Consequently, MCS/NiSe2 nanocomposite could obtain the highest H2 evolution rate of 22.5 mmol g−1 h−1 under Vis-NIR light irradiation, reaching 3.2 times of MCS. This work provides a novel idea for the rational design of efficient photocatalysts by making full utilization of the synergetic effects of co-catalyst modification and photothermal effect without external heating source.

NOx formation mechanism of plasma assisted ammonia combustion: A reactive molecular dynamics study

The effects of ionization ratio (α) on the reaction rate of NH3 combustion and the formation characteristics of NOx are studied by ReaxFF MD, and the formation mechanism of NOX in plasma assisted NH3 combustion are analyzed from the molecular level. It is found that the maximum growth rate of NOX gradually slows down with increasing reaction system temperature. The plasma promotes NOX formation at the initial stage of NH3 combustion, and when the nitrogen-containing radicals are consumed, the non-nitrogen-containing components will inhibit NO formation. When the α is 25%, the NH3 reaction rate reduces slightly. This is attributed that the proportion of NH2/H is the larger at this lower α. The plasma effect at lower α = 25% enhances the N2 formation path from NH3 by the primary reaction pathway of NH3→NH2→NH→NNH→N2, and the intermediate NH consumes some of the NO to form N2 by NH + NO↔HN2O and HN2O↔N2+OH. As α increases to 50%, the plasma leads to the direct generation of NO from NH by NH + OH↔H2NO and H2NO + O↔H2O + NO, which makes the maximum of NO increase.

Enhanced tribocatalytic pollutant degradation through tuning oxygen vacancy in BaTiO3 nanoparticles

Effective control of pathogen contamination is crucial for maintaining water security. This study investigated the impact of oxygen vacancys (OVs) content on the tribocatalytic performance of ferroelectric barium titanate (BTO) and its suitability as a tribocatalyst for water disinfection. The degradation efficiency of Rhodamine B (RhB) was increased by nearly 4-folds due to the appropriate OVs on the surface of BTO. In addition, experimental variables including the concentration of dissolved oxygen in the reaction solution, the temperature of reaction system, friction frequency, and charge transfer capacity were identified as important factors for tribocatalysis. Atom force microscope (AFM) imaging and density functional theory (DFT) calculations indicated that OVs couldn’t improve the electron transfer ability during BTO tribocatalysis. The excellent tribocatalytic performance of BTO-VO2 is due to the effective separation of electron and hole and the reduction of band gap. It is proposed that the tribocatalytic performance of BTO is determined by the electron transfer on the surface and the electron transition inside the catalyst. The simple stirring of BTO-VO2 tribocatalysts can effectively degrade organic molecules and inactivate model bacteria, which provides insights into the feasibility of wastewater treatment under dark conditions.

Preparation of CuFe2O4 composite metal oxides and selective oxidation of benzyl alcohol

Using iron nitrate and copper nitrate as raw materials, mesoporous material SBA-15 as template agent and n-hexane as solvent, CuFe2O4 samples of mesoporous loaded composite metal oxide catalysts were successfully prepared by calcination at 600 °C. The samples were characterized by X-ray diffraction (XRD), thermogravimetric-differential scanning analysis (TG-DSC), and scanning electron microscopy (SEM). The selective oxidation of benzyl alcohol by CuFe2O4 under different catalytic conditions was investigated using benzyl alcohol as a model compound, and the oxidation products were analyzed by high performance liquid chromatography (HPLC). The results showed that the CuFe2O4 catalyst prepared by calcination at 600°Cwas the best. The best selective oxidation conditions were achieved at a reaction system temperature of 90 °C, a catalyst dosage of 4 g/L, a molar ratio 1:1 of H2O2 dosage to benzyl alcohol, and a reaction time of 4 h. The conversion of benzyl alcohol under this condition was 66.95%, and the selective conversion of benzaldehyde was 96.07%. This indicates that CuFe2O4 is a composite metal oxide with high selective oxidation of benzyl alcohol and has wide application prospects.

Preparation of Mesoporous Supported CuCo2O4 Catalyst and Selective Oxidation of Benzyl Alcohol

Using poly (ethylene oxide)-poly (propylene oxide)- poly (ethylene oxide) (P123), tetraethyl silicon (TEOS), HCl, n-butanol as raw materials, SBA-15 template was prepared by liquid phase reaction method. Using SBA-15 as template, Cu(NO3)2·3H2O and Co(NO3)2·6H2O as raw materials and n-hexane as solvent, mesoporous CuCo2O4 composite metal oxide was prepared by hard template nano-casting. The composite metal oxides were characterized by thermo gravimetric differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Taking benzyl alcohol as the target, the effects of reaction temperature, different catalyst dosage, reaction time and molar ratio of benzyl alcohol to hydrogen peroxide on selective oxidation of benzyl alcohol by CuCo2O4 were studied, and the oxidation products were analyzed by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). The results show that the sample of CuCo2O4 metal composite calcined at 700 °C has the highest purity, and the average particle size is about 500 nm. The optimum conditions for selective oxidation of benzyl alcohol by CuCo2O4 are reaction system temperature of 80 °C, catalyst dosage of 8 g/L, reaction time 3h, the molar ratio 1:1 of hydrogen peroxide to benzyl alcohol. Under the optimum condition, the conversion rate of benzyl alcohol is 78.13% and the recovery rate of benzaldehyde is 56%. Mesoporous CuCo2O4 is a composite metal oxide with good selective oxidation of benzyl alcohol, which has a wide application prospect.

In situ construction of oxygen deficient MoO3-x nanosheets/porous graphitic carbon nitride for enhanced photothermal-photocatalytic hydrogen evolution

In this work, the photocatalysts containing oxygen-deficient molybdenum oxide and macroscopic three-dimensional porous graphitic carbon nitride phase composite (MoO3-x/PCN) were prepared by in situ self-assembly method. The crystal phase and structure were characterized by XRD, XPS, FT-IR, SEM, and TEM measurements. Hydrogen production results showed that introducing of MoO3-x resulted in a higher hydrogen production rate of MoO3-x/PCN composite catalyst than that of PCN. Among them, the highest hydrogen production rate of 2336.15 μmol g−1 h−1 was achieved for MoO3-x-10/PCN, which was 2.23 times higher than PCN (1048.00 μmol g−1 h−1). When the reaction system temperature was 100 °C, the photothermal hydrogen production rate of MoO3-x-10/PCN was 8902.00 μmol g−1 h−1, which was 3.81 times higher than that at room temperature. PL spectra, UV–vis spectra and photoelectrochemical measurements showed that the localized surface plasmon resonance (LSPR) effect of MoO3-x effectively enhanced the photo response range and increased the temperature of the reaction system. ESR measurements showed that he composites should follow the Z-scheme charge transfer mechanism, the electrons in the CB of MoO3-x further migrate to the VB of PCN, which hinders the charge complexation in MoO3-x and PCN, improving the hydrogen production activity. This study provides a new idea for constructing a plasma-based photothermal synergistic catalytic hydrogen production strategy.

Preparation of a biobased polyelectrolyte complex from chitosan and sodium carboxymethyl cellulose and its antibacterial characteristics

Using chitosan (CTS) and sodium carboxymethyl cellulose (CMCNa) as raw biobased materials, polyelectrolyte complex (PEC), which is the product of strong electrostatic interaction between two bio-based polyelectrolytes with opposite charges, was attempted to prepare. To enlarge the reactive contact area between CTS and CMCNa, the crosslinked vacuolar structure of PEC was prepared without addition of cross-linked agent. The preparation conditions had a significant impact on the yield of PEC and the bibulous rate of PEC. When pH, mass ratio of CMC-Na-to-CTS, stirring speed and reaction system temperature were 5, 1:2 [(1 wt% CMCNa, 2 wt% CTS), CMC-Na:CTS = 1:1 (v/v)], 800 rpm, 2 min and 25 °C, the yield of PEC reached 71.2 %. The prepared PEC was characterized by XRD and FT-IR. Afterwards, the antibacterial performance of PEC was examined. The prepared PEC had certain bacteriostatic effect on gram-positive and gram-negative bacteria. The bacteriostasis ratios of PEC against Escherichia coli and Staphylococcus aureus were 18.7 % and 31.3 %, respectively. By controlling the combination parameters of the preparation system, an effective strategy was successfully developed for preparation of biobased PEC with bacteriostatic and crosslinked vacuolar structure through simple physical blending without the application of additional crosslinker.

An improved Hummers method to synthesize graphene oxide using much less concentrated sulfuric acid

The production of graphene oxide with less acid is beneficial to reduce the costs and lower the impact on the environment, but it is still a great challenge. In this work, a relatively simple, safe method for synthesizing graphene oxide with much less acid (decrease ∼40%) is proposed. With assistance of the heat absorbed from environment and reaction system, the temperature of reaction system of low acid can be well controlled. More interestingly, the graphite can be completely oxidized into graphite oxide by using much less acid, with lowering the production of high-concentration aqueous waste acid (> 1 mol/L, decrease ∼40%). A series of characterizations show that the prepared graphene oxide has similar yield and functional groups compared with that of using the conventional method. This work provides a safe and environmentally friendly choice for the large-scale production of graphene oxide and its derivative materials. Graphene oxide was synthesized by using much less concentrated sulfuric acid. The graphite can be completely oxidized into graphite oxide, with lowering the production of high-concentration aqueous waste acid (> 1 mol/L, decrease ∼40%).

Fe3O4 nanoparticles-mediated solar-driven enzymatic PET degradation with PET hydrolase

Cost-effective and eco-friendly treatment or recycled use of poly (ethylene terephthalate) (PET) is highly desired. Enzymatic PET degradation is considered a promising approach, but currently available PET hydrolases (PETases) have low activity at ambient temperature. Thus, elevating the reaction system temperature in a cost-effective way becomes a key to the economical enzymatic PET degradation. Herein, we proposed solar-driven enzymatic PET degradation with DuraPETase, a stable mutant of PETase, by using Fe3O4 nanoparticles (NPs) as the solar-to-thermal agent. Simulated solar irradiation could elevate the suspension of Fe3O4 NPs from 25 °C to 46 °C for the effective PET degradation. The enzyme immobilized onto Fe3O4 NPs, DuraPETase@Fe3O4, had higher stability than free DuraPETase, but a 10-d PET degradation experiments under simulated solar irradiation revealed that free DuraPETase in the presence of Fe3O4 NPs was approximately three times more effective than the DuraPETase@Fe3O4 system because of the superiority of free DuraPETase in degrading PET. This implies that enzyme immobilization is unnecessary in such a single-use system. By contrast, the DuraPETase-only system showed only 15.5% efficiency of the Fe3O4-mediated solar-driven system with free DuraPETase. The research demonstrated the potential of the Fe3O4-mediated solar-driven enzymatic PET degradation strategy for further development in different practical scenarios

Chemical looping gasification with a CuFe2O4-enhanced phosphogypsum oxygen carrier during reduction in a fluidized bed reactor

Aiming to solve the H2S releasing and reduce the temperature of reaction system from a Phosphogypsum (PG) Oxygen carrier (OC) during Chemical looping gasification (CLG), a new CuFe2O4-enhanced PG-CuFe2O4 OC for reducing lignite in the CLG process was explored. In this study, using lignite as a fuel, X-ray fluorescence spectrometer (XRF), Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) were used to characterize the reduction process of PG-CuFe2O4. Thermodynamics and kinetics analyses of CuFe2O4-enhanced PG OC in a fluidized bed during reduction with lignite were conducted to better understand H2S capture and syngas production. The experimental results and mechanism analysis were as follows. In the fluidized bed reactor, to produce syngas with the highest possible proportions of CO and H2, the optimum reaction conditions were: reaction temperature should not exceed 1123 K, but 1073 K is recommended; the water vapor content R = 0.2; and PG-CuFe2O4 OC and lignite oxygen carbon ratio X = 0.6. During the reduction reaction, S6+ was reduced to S2− and Cu2+ was reduced to Cu1+ and Cu0. In addition, Fe3+ was reduced to Fe3/8+ and a small amount of Fe3/8+ was reduced to Fe2+. The mechanisms of oxygen release by OC during the reduction process followed the priority order: CaSO4 ˃ CuO ˃ Cu2O ˃ Fe2O3 ˃ Fe3O4 ˃ FeO. The PG-CuFe2O4 had an excellent H2S capture ability and the reduction intermediate products of Fe3O4, Cu, and FeS played important roles in the capture of H2S during the reaction. Using Kissinger and Flynn-Wall-Ozaw methods, the mechanism model of PG-CuFe2O4 OC during reduction process was confirmed, and the reaction kinetics model was dXdt=1.98×1018exp-215.02×103RT×32⊢X1/3-1-1.

Mild steel corrosion inhibition by synthesized 7-(Ethylthiobenzimidazolyl) Theophylline

The corrosion inhibition of mild steel by 7-(ethylthiobenzimidazolyl) theophylline (7-ETBT) in 1 M HCl medium was investigated through weight loss and Tafel polarization techniques within a temperature range of 298 to 318 K. The inhibition efficiency depends on the concen­tration of 7-ETBT and reaction system temperature. The maximum inhibition efficiency values of 90.73 and 87.06 %, respectively, were estimated using both weight loss and Tafel polarization techniques at 298 K. The results suggest spontaneous and predominant physical adsorption of 7-ETBT on the metal surface which obeys Langmuir isotherm model. Furthermore, Tafel polarization method revealed that 7-ETBT is a mixed-type inhibitor. Po­tentiodynamic polarization results are in accordance with weight loss data to a good extent.

Phosphoric Acid: A Key Role in Control of Structure and Properties of Vanadium Phosphorus Oxide Catalysts During Synthesis

AbstractThe catalytic performance of vanadium phosphorus oxide (VPO) catalysts is closely related to the synthetic conditions of precursors. Herein, the role of phosphoric acid during VPO precursors synthesis process was thoroughly studied by investigating the morphology, crystal phase composition, and surface chemical property of VPO catalysts and their precursors. The H3PO4 concentration, the temperature of reaction system at the time of H3PO4 adding, and H3PO4 adding speed were optimized to prepared efficient VPO catalysts which applied in selective oxidation of n‐butane to produce maleic anhydride (MA). The obtained VPO catalyst by adding 85 % H3PO4 at or above 110 °C with the speed of approximate 1.1 mL/min could exhibit promising catalytic performances, which are 93.8 % of n‐butane conversion and 62.4 % of MA yield at 420 °C. Thus, this study emphasized the role of H3PO4 adding during VPO synthesis process, which is favorable to understand and fabricate the compositional, structural, and morphological properties of VPO catalysts.

Direct generation of poly(ionic liquids) on mesoporous carbon via Diels–Alder and multicomponent reactions for ultrafast adsorptive removal anionic organic dye with high efficiency

The porous materials have been extensively explored for various applications especially for the environmental treatment. In this work, we reported a novel strategy for the surface modification of mesoporous carbon (MC) that relied on an efficient and green Diels–Alder [4 + 2] cycloaddition and the multicomponent Radziszewski reactions for the first time to in-situ generate poly (ionic liquids) (PIL) on the surface of MC. The resulting MC@PIL composites have been characterized using a series of instrumental techniques to elucidate their morphology, chemical compositions and other properties. Batch experiments towards adsorbing Congo red (CR) with contact time, initial concentration, variable pH and reaction system temperature were conducted to evaluate the adsorption behaviors. Furthermore, thermodynamic analysis of adsorption process is also discussed. The results demonstrated that CR could be rapidly adsorbed on MC-PIL composites within 10 min and displayed obvious enhancement adsorption capacity (331.49 mg/g) towards CR as compared with pristine MC. In addition, the adsorption/desorption cycle of the MC@PIL composites was also tested. The results show that the adsorption capacity of the third adsorption-desorption cycle can reach 199.0223 mg/g and desorption yield above 80%. Considered the good designability of molecules involved in Radziszewski reaction, many functionalized MC could thus be fabricated and these PIL functionalized composites should be efficient and promising candidates for removal of different pollutants from wastewater.

Metolazone compound as corrosion inhibitor for API 5L X-52 steel in hydrochloric acid solution

The aim of this research is to evaluate the inhibitive effect of metolazone on API 5L X-52 steel in 2 M HCl solution using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization techniques within a temperature range of 303 to 323 K. Scanning electron microscopy (SEM) was also employed to study the morphology of the corroded coupons in 2 M HCl solution and in the presence of the inhibitor. The efficiency of the inhibition depends on the concentration of metolazone and reaction system temperature. The maximum inhibition efficiency values were 92.7 and 90.7%, respectively, for both EIS and polarization techniques at the temperature of 303 K. The electrochemical impedance spectra (EIS) studies reveal that the process of inhibition is through charge transfer. Potentiodynamic polarization (PDP) studies showed that metolazone is mixed-type inhibitor. The metolazone adsorption characteristics on API 5L X-52 steel surface was found to be spontaneous and obeyed Langmuir adsorption isotherm and the mechanism of adsorption suggest chemisorptions. The inhibition efficiency of metolazone drug obtained by electrochemical methods was in good relationship with each other.
 
 KEY WORDS: Metolazone drug, API 5L X-52 Steel, SEM, Electrochemical, Corrosion inhibition
 
 Bull. Chem. Soc. Ethiop. 2020, 34(2), 407-418
 DOI: https://dx.doi.org/10.4314/bcse.v34i2.16

Issues in Preparation of Metal-Lignin Nanocomposites by Coprecipitation Method

Chemical coprecipitation technique is proven to be a beneficial method to prepare uniformly mixed catalyst metal and Kraft lignin precursors. Coprecipitation is a simple, yet very complex process which is highly sensitive to the reaction conditions, particularly temperature. In an exothermic coprecipitation process, the reaction rate can become uncontrollable over certain temperatures which could lead to a thermal runaway reaction. In this work, metal-lignin nanocomposites were synthesized by coprecipitation of metal (M) salts and Kraft lignin. Kraft lignin and metal salts were dissolved in organic solvents and DI water, respectively, to make lignin solution/suspension and metal salt aqueous solution. The aqueous solutions of metal salts were then added to the lignin solutions/suspensions and mixed well, resulting in chelation of transition metal ions to the functional groups of lignin chains and co-precipitation of metal-lignin composites from the solvents. To develop a safe process for producing M-lignin composites in a large volume, potential reactions, exothermic or endothermic processes, hazards gases, and volatiles were evaluated during the coprecipitation process. The effects of transition metal type, solvent selection, concentration of metal salts, and initial solution temperature on the interactions between metal ions and Kraft lignin, metal uniformity in the lignin matrix, and morphology of the metal-lignin composites were investigated during the coprecipitation process. Cu, Mo, Ni, and Fe were investigated as the transition metals for the metal-lignin composites. Fenton or Fenton-like reactions were discovered to occur during the Fe- and Cu-lignin coprecipitation process and tremendous heat evolved, which lead to the overshoot of the reaction system temperature in a very short time (i.e. a few seconds). Significant amounts of CO2 and toxic NO2 gasses were released during the coprecipitation process when Fenton or Fenton-like reactions occurred. No interaction or a very weak interaction occurred between lignin and Mo(VI) ions when mixing both solutions. Ni ions were coordinated strongly to oxygen-containing functional groups in lignin, but no Fenton or Fenton-like reaction was detected during Ni-lignin coprecipitation. Fenton reaction or Fenton-like reaction occurred when tetrahydrofuran (THF) and acetone were used to dissolve Kraft lignin, and the reaction became highly fierce and unmanageable with increasing of iron content in the composite. The reaction initialization time was shortened with increase of initial solution temperature and thermal runaway reaction might occur if the initial mixing temperature reached 60 °C or above.

Efficient photothermocatalytic hydrogen production performance over a graphene-titanium dioxide hybrid nanomaterial

Here, Graphene@TiO2 nanomaterials were prepared for photothermocatalytic H2 production to make full-use of solar spectrum. The H2 evolution rate (HER) was 17.6 μmol/h and 89.8 μmol/h at room temperature and 90 °C, respectively. Interestingly, it could sharply increase to 436.5 μmol/h when the temperature reached 110 °C, which was about 24.8 times that of under room temperature. The introduction of graphene effectively promoted the specific surface area and pore volume of the composite, thus, contributing to the quick diffusion of reactants. Meanwhile, graphene absorbed and converted the energy of long wavelength photons into heat via photothermal effect, thus, enhancing the temperature of reaction system. The enhanced HER might be attributed to the existence of gas-liquid two-phase flow in micro-boiling state, the strengthened migration/diffusion rate of sacrificial reagent molecules, and as well as the excitation of adsorbed reactant molecules stemming from the elevated temperature. Our work should be valuable for the design of novel and efficient photothermocatalytic hydrogen production system driven by full-spectrum of sun light.

КАВІТАЦІЯ У КОМБІНОВАНИХ ТЕХНОЛОГІЯХ ОЧИЩЕННЯ СТІЧНИХ ВОД ВІД ТОЛУЕНУ

The use of acoustic and hydrodynamic cavitation and their combinations with other methods (reagent treatment – hydrogen peroxide, Fenton reagent, ozone, etc.) for wastewater treatment from dispersed solids and organic compounds is analyzed. The feasibility of combining cavitation with rea-gent treatment to increase the degree of pollutant degradation has been demonstrated. A characteristics of the spectroscopy method in ultraviolet and visible spectral ranges is given to determine the concentration of toluene in wastewater imitation. The dependences of toluene concentration and the reaction system temperature on the duration of cavitation treatment at different values of the specific power of ultrasonic radiation, the pressure at the entrance to hydrodynamic cavitator, different reagent modes are presented. The degree of toluene degradation and the rate constant of this process for different parameters of cavitation processing are calculated. It is found that an increase in the specific power of ultrasonic radiation from 53.3 to 83.3 W/dm3 has caused a decrease in the degree of toluene degradation by 11.2 % (from 82.5 to 71.3 %), and the rate constant by 2.5 times (from 5.6·10-4 to 2.2·10-4 s-1), which is explained by two factors: the formation of Babstones and the change in the structure of the fluid according to Frenkel's kinetic theory. It is established that the use of combined technology (acoustic cavitation + hydrogen peroxide) allows to increase the rate of toluene degradation from 82.5 to 84 % and the rate constant by 26.8 % (from 5.6·10-4 to 7.1·10-4 s-1). It is determined that the combination of hydrodynamic cavitation and reagent treatment (hydrogen peroxide) allows to increase the rate of toluene degradation by 2.5 % (from 95.8 to 98.3 %). By comparing the rate constants of toluene degradation and the degradation rates for combined technologies (acoustic cavitation + H2O2; hydrodynamic cavitation + H2O2), it is found that hydrodynamic cavitation is much more efficient than acoustic one.

Gold nanoparticles supported by amino groups on the surface of magnetite microspheres for the catalytic reduction of 4-nitrophenol

Fe3O4/P(GMA-DVB)/PAMAM/Au microspheres are fabricated to research the catalytic performances to 4-nitrophenol. In the preparation process, Fe3O4 microspheres act as magnetic cores, PAMAM dendrimers growing up on the surface of P(GMA-DVB) polymer work as carriers, and Au nanoparticles serve as catalytic materials. The stability of the prepared microspheres is evaluated by successively catalytic experiments to measure the conversion of 4-nitrophenol, and catalytic efficiency can still maintain up to 78.7% after ten cycles. Moreover, the effects of major factors including the concentration of the prepared microspheres and the temperature of reaction system on the conversion of 4-nitrophenol are also investigated in detail. The manuscript reveals that 4-nitrophenol can be almost converted to 4-aminophenol within 7 min at 45 °C in the case of using 1.0 g/L Fe3O4/P(GMA-DVB)/PAMAM/Au microspheres. Such excellent catalytic properties are ascribed to the optimum structure of the prepared microspheres, which favors the sufficient contact between Au nanoparticles and 4-nitrophenol. The results and strategies exhibited here provide insight into the preparation of sophisticated structures of catalysts to treat wastewater.

Visible light responsive CdS sensitized TiO2 nanorod array films for efficient photocatalytic reduction of gas phase CO2

Abstracts In this letter, an effective photocatalytic reduction of CO2 by using CdS-Cu2+/TiO2 nanorod array films photocatalyst under visible light was studied. TiO2 nanorod array films were prepared by the hydrothermal method, after which Cu2+ ions and CdS quantum dots (QDs) were deposited on the TiO2 nanorod arrays using the ultrasonic-assisted sequential cation adsorption method and successive ionic layer adsorption and reaction (SILAR) method respectively. The composition, morphology and optical property of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectric spectroscopy (XPS) and UV–vis diffuse reflectance spectra (DRS). The loading amount of CdS QDs was regulated by controlling the deposition cycles which demonstrates correspondingly optical behaviors. Their photocatalytic activities were evaluated by reduction of gas-phase CO2 to estimate the ethanol yield under various operating parameters, including the CdS QDs concentration, CO2 flow rate and reaction temperature. The experiment results showed that when the SILAR method cycle deposition was two, the reaction product yield reached the maximum, and the ethanol yield was 109.12 μmol/g-cat h at a flow rate of 4 mL/min and under the reaction system temperature of 80 °C. The highly efficient photocatalytic activities of CdS-Cu2+/TiO2 nanorod array films in the reduction process of CO2 were attributed to the combination of one-dimensional (1D) nanostructure with decorating Cu2+ ions and CdS QDs, which restrain recombination of the electron hole pairs and broaden the visible-light response. In addition, the photocatalytic mechanism was discussed to understand the experimental results over the CdS-Cu2+/TiO2 nanorod array films.