n-Hexadecane and pyrene biodegradation and metabolization by Rhodococcus sp. T1 isolated from oil contaminated soil

The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. T1 was isolated from oil contaminated soil. Strain T1 could remove 90.81% n-hexadecane(2 vol%) and 42.79% pyrene(200 mg·L~(-1)) as a single carbon within 5 days, respectively. Comparatively, the degradation of pyrene increased to 60.63%, but the degradation of n-hexadecane decreased to 87.55% when these compounds were mixed. Additionally, identification and analysis of degradation metabolites of Rhodococcus sp. T1 in the above experiments showed that there were significant changes in alanine, methylamine, citric acid and heptadecanoic acid between sole and dual substrate degradation. The optimal conditions for degradation were then determined based on analysis of the pH, salinity, additional nutrient sources and liquid surface activity.Under the optimal conditions of pH 7.0, 35 °C, 0.5% NaCl, 5 mg·L~(-1) of yeast extract and 90 mg·L~(-1) of surfactant,the degradation increased in single or dual carbon sources. To our knowledge, this is the first study to discuss metabolite changes in Rhodococcus sp. T1 using sole substrate and dual substrate to enhance the long-chain alkanes and PAHs degradation potential.     

A review of internally heat integrated distillation column

The energy consumption of distillation operation determines the amount of energy consumption throughout the chemical separation process. A heat integrated distillation column(HIDiC) could greatly reduce the irreversibility of the distillation process, so it gradually becomes a research hotspot. There are two major techniques for heat integration in HIDiC: internally and externally. This review paper describes the major research aspects of an internally heat integrated distillation column(IHIDiC), including the heat transfer models, various design structures(including the two-column HIDiC, Concentric HIDiC, Shell and tube HIDiC, Plate-fin HIDiC and the Super HIDiC, etc.), experimental research, simulation and optimization, process control research, as well as industrial plants and potential industrial applications. Among them, the heat transfer performance of various structures was analyzed of the various design structures based on experimental research, the effects of different factors(including relative volatility, reflux ratio, compression ratio, etc.) on HIDiC energy consumption or TAC is summarized in the simulation part. The calculation methods of the overall heat transfer coefficient and heat transfer models are summarized. The various optimization algorithms and optimization results of simplified HIDiC are summarized in the optimization part. The research status and the key technical issues in various aspects of HIDiC are summarized in this paper. In order to meet the requirements of industrial energy efficiency,the selection of multi-component separation distillation configurations needs to be considered more diversified,and internal complex coupling relationship of HIDiC needs to be further studied.     

Applications of high-gravity technologies in gas purifications: A review

The traditional gas purification techniques such as wet gas desulfurization, with their advantages of large-scale implementation and maturity, have still been widely used. However, the main drawback of these techniques is the low transfer efficiency, which normally needs towers as tall as tens of meters to remove the pollutants. Therefore, new technologies which could enhance the mass transfer efficiency and are less energy-intensive are highly desirable. As a process intensification technology, high-gravity technology, which is carried out in a rotating packed bed(RPB), has recently demonstrated great potential for industrial applications due to its high mass transfer efficiency, energy-saving, and smaller volume. This consequently provides higher efficiency in toxic gas removal, and can significantly reduce the investment and operation costs. In this review, the mechanism,characteristics, recent developments, and the industry applications of high-gravity technologies in gas purifications, such as hydrogen sulfide, nitrogen oxide, carbon dioxide, sulfur dioxide, volatile organic compounds and nanoparticle removal are discussed, most of the demonstration projects and practical application examples in gas purification come from China. The perspective and prospective of this technology in gas purification and other fields are also briefly discussed.     

Hot corrosion behavior of TiO2 doped,Yb2O3 stabilized zirconia exposed to V2O5 + Na2SO4 molten salt at 700–1000 °C

3.5 mol% Yb₂O₃ stabilized zirconia (YbSZ) doped with 10 mol% TiO₂ (Ti-YbSZ) was produced, and its hot corrosion behavior exposed to Na₂SO₄ + V₂O₅ molten salt was investigated. The as-fabricated ceramic mainly consists of metastable tetragonal (t′) phase. When exposed to the molten salt at 700 °C, 800 °C, 900 °C and 1000 °C for 2 h and 10 h, YbVO₄ and m-ZrO₂ formed as corrosion products due to chemical reactions between the ceramics and the salt. Ti⁴⁺ in Ti-YbSZ solid solution keeps stable during the hot corrosion tests, which acts as a stabilizer for ZrO₂, preventing total decomposition of the t′ phase. After the hot corrosion tests, Ti-YbSZ has an apparently lower m phase content than Y₂O₃ doped Zirconia and YbSZ, indicative of better corrosion resistance. The hot corrosion mechanism of Ti-YbSZ is proposed based on Lewis acid-base rule, phase diagrams and thermodynamics.     

Support surface pore structures matter: Effects of support surface pore structures on the TFC gas separation membrane performance over a wide pressure range

In this work, the effects of support surface pore structures(including surface pore size, surface pore density and surface porosity) on the performance of thin film composite(TFC) gas separation membrane over a wide pressure range(from 0.3 to 2.0 MPa) were studied. To fulfill it, the polysulfone(PSf) supports with different surface pore structures were prepared. Two kinds of wide-accepted polymeric membrane materials, i.e., polyvinylamine(PVAm) and Pebax 1657 copolymer, were used as skin layer materials. We pointed out for the first time that the support surface average pore size and pore density could affect the chain mobility of polymer of skin layer at the support surface pore entrance, then, can affect the TFC membrane performance. Besides, we also discussed the effects of support on the TFC membrane performance when the feed pressure changes for the first time. This work can provide guidance for choosing a suitable support for TFC gas separation membrane.     

Increased sedimentation of a Pseudomonas–Saccharomyces microbial consortium producing medium chain length polyhydroxyalkanoates

Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs) production,which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia.Here,a medium chain length PHAs(mcl-PHAs) producing Pseudomonas-Saccharomyces consortium with xylose as the main substrate was studied.Mcl-PHAs accumulation increased from 12.69 mg·L~(-1) to 152.3 mg·L~(-1) without any optimization method.The presence of Saccharomyces cerevisiae,though in a relatively low concentration,improved the sedimentation of cell mass of the mixed culture by 60%.Reasons for better sedimentation of the consortium were complex:first,the length of Pseudomonas putida increased two to three times in the consortium;second,the positive surface charge of P.putida was neutralized by S.cerevisiae;third,the adhesion proteins on the surface of S.cerevisiae interacted with the P.putida.     

Hot corrosion behavior of Y4Al2O9 ceramics for thermal barrier coatings exposed to calcium-magnesium-alumina-silicate at 1250 °C

The degradation of thermal barrier coatings (TBCs) by calcium-magnesium-alumina-silicate (CMAS) attack has become increasingly dramatic. Y₄Al₂O₉ ceramic, a new potential TBC candidate, has received an increasing attention. In this study, porous Y₄Al₂O₉ ceramic pellets, instead of actual TBCs, are used to investigate the CMAS corrosion resistance at 1250 °C. Results indicate that Y₄Al₂O₉ reacts with CMAS melt to form an impervious sealing layer mainly containing Ca-Y-Si apatite, which could mitigate CMAS further penetration. Once the sealing layer formed, further reaction would occur above the layer accompanying by the recession of sealing layer. This process is probably related to a solid state diffusion.     

Improvement of Al3+ ion conductivity by F doping of (Al0.2Zr0.8)4/3.8NbP3O12 solid electrolyte for mixed potential NH3 sensors

New Al³⁺ ion conducting solid electrolytes (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x(0?≤x?≤?0.4) with Nasicon-structure are successfully prepared by solid state reaction method. The influences of the doped F^- content on the properties of the (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x samples are investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The results show that F^- doping can effectively improve the sinterability and the total conductivity of the (Al_0.2Zr_0.8)_4/3.8NbP₃O_12-xF_2x samples. Among the solids series, (Al_0.2Zr_0.8)_4/3.8NbP₃O_11.7F_0.6 shows the highest conductivity of 1.53?×?10^?3 S?cm^?1at 500?°C, which is approximately 7.9 times higher than that of the undoped (Al_0.2Zr_0.8)_4/3.8NbP₃O₁₂. The ion transference number of the samples is higher than 0.99 at 300–700?°C. On the basis of the promising properties, a mixed-potential type NH₃ sensor based on (Al_0.2Zr_0.8)_4/3.8NbP₃O_11.7F_0.6 electrolyte and In₂O₃ sensing electrode has been developed. The sensing performance of the sensor is evaluated. The mixed-potential type sensor can work at relatively low temperatures of 200–350?°C and an excellent sensitivity of 99.71?mV/decade at 250?°C is obtained. The sensor also displays excellent stability and reproducibility, accompanied by low cross-sensitivities to CO₂, CH₄ and H_2.     

Engineering an ultrathin amorphous TiO2 layer for boosting the weatherability of TiO2 pigment with high lightening power

TiO₂ pigments are typically coated with inert layers to suppress the photocatalytic activity and improve the weatherability. However, the traditional inert layers have a lower refractive index compared to TiO₂, and therefore reduce the lightening power of TiO₂. In the present work, a uniform, amorphous, 2.9-nm-thick TiO₂ protective layer was deposited onto the surface of anatase TiO₂ pigments according to pulsed chemical vapor deposition at room temperature, with TiCl₄ as titanium precursor. Amorphous TiO₂ coating layers exhibited poor photocatalytic activity, leading to a boosted weatherability. Similarly, this coating method is also effective for TiO₂ coating with amorphous SiO₂ and SnO₂ layers. However, the lightening power of amorphous TiO₂ layer is higher than those of amorphous SiO₂ and SnO₂ layers. According to the measurements of photoluminescence lifetime, surface photocurrent density, charge-transfer resistance, and electron spin resonance spectroscopy, it is revealed that the amorphous layer can prevent the migration of photogenerated electrons and holes onto the surface, decreasing the densities of surface electron and hole, and thereby suppress the photocatalytic activity.     

Catalytic depolymerization of calcium lignosulfonate by NiMgFeO_x derived from sub-micron sized NiMgFe hydrotalcite prepared by introducing hydroxyl compounds

A new method for regulating the synthesis of Ni Mg Fe hydrotalcites(NMF LDHs) with the addition of hydroxyl compounds was proposed. A series of NMF LDHs were prepared by the above method, and then were calcined to obtain the Ni Mg Fe Ox(NMFOx) samples. The NMFOxsamples were characterized by XRD,SEM, TG-DTG, XPS and CO2-TPD, respectively. The catalytic performance of NMFOxfor depolymerizing calcium lignosulfonate(CLS) was evaluated by hydrothermal reaction. The results showed that the addition of hydroxyl compounds favored reducing the particle sizes of NMF LDHs. For the depolymerization of CSL, the yield of liquid product increased from 45% to 75.8% with the addition of NMFOx-ethanol(NMFOxET). The liquid products were mainly phenolics, aromatics, ketones and esters. The total selectivity of oxy-containing compounds was over 90.6%, among them, the phenolics were approximately 35.2%. The valence of Ni and Fe, crystalline phase and basicity almost remained unchanged. The NMFOx-ET samples were recycled for the depolymerization of CLS, moreover, the NMFOx-ET samples had high activity and stability after 4 cycles.     

Aminolysis of ethyl acetate in continuous flow and its reaction kinetics

The aminolysis of ethyl acetate was promoted significantly via continuous reaction in a tubular reactor. N-propylacetamide was thus synthesized without presence of solvent and catalyst. The optimum conditions were obtained as follows:the reaction temperature is 218℃, the reaction pressure is 3.5 MPa, the molar ratio (ethyl acetate:N-propylamine) is 1:1, and the residence time is 350 min. Accordingly, the conversion of ethyl acetate is up to 94.8%. Furthermore, the kinetics of the rapid reaction stage (when the conversion of ethyl acetate is 20%-80%) can be expressed as lnk--4629:44 1/T + 2:1366, and the apparent activation energy is E_a=38489 J·mol^-1.     

Wind field reconstruction for the dispersion modeling of accidental chemical spills on complex geometry

Chemical spills on complex geometry are difficult to model due to the uneven concentration distribution caused by air flow over ground obstacles. Computational fluid dynamics (CFD) is one of the powerful tools to estimate the building-resolving wind flow as well as pollutant dispersion. However, it takes too much time and requires enormous computational power in emergency situations. As a time demanding task, the estimation of the chemical spill consequence for emergency response requires abundant wind field information. In this paper, a comprehensive wind field reconstruction framework is proposed, providing the ability of parameter tuning for best reconstruction accuracy. The core of the framework is a data regression model built on principal component analysis (PCA) and extreme learning machine (ELM). To improve the accuracy, the wind field estimation from the regression model is further revised from local wind observations. The optimal placement of anemometers is provided based on the maximum projection on minimum eigenspace (MPME) algorithm. The fire dynamic simulator (FDS) generates high-resolution data of wind flow over complex geometries for the framework to be implemented. The reconstructed wind field is evaluated against simulation data and an overall reconstruction error of 9% is achieved. When used in real case, the error increases to around 12% since no convergence check is available. With parameter tuning abilities, the proposed framework provides an efficient way of reconstructing the wind flow in congested areas.     

Temperature stable 0.35Ag2MoO4-0.65Ag0.5Bi0.5MoO4 microwave dielectric ceramics with ultra-low sintering temperatures

In this study, the novel temperature-stable (1-x)Ag₂MoO₄-xAg_0.5Bi_0.5MoO₄ microwave dielectric ceramics were prepared by a modified solid-state reaction method. The phase composition, microstructures and microwave dielectric properties of the (1-x)Ag₂MoO₄-xAg_0.5Bi_0.5MoO₄ ceramics were investigated. All the compounds can be sintered well at ultra-low temperatures (<540 °C). The XRD and SEM analysis indicate that the Ag₂MoO₄ and the Ag_0.5Bi_0.5MoO₄ can coexist with each other. When x = 0.65, the ceramics exhibit the best microwave dielectric properties with a relative permittivity of 23.9, a Q × f value of 16,200 GHz (at 7.3 GHz) and a near-zero TCF value of -2.4 ppm/°C at 520 °C. The results indicate that temperature-stable (1-x)Ag₂MoO₄-xAg_0.5Bi_0.5MoO₄ ceramics are promising candidates for low temperature co-fired ceramics (LTCC) applications.     

Methodology for dependence-based integrated constitutive modelling: An illustrative application to SiCp/Al composites

In industrial forming and machining process, the large plastic deformation of material takes place in wide loading ranges of strain-rate and forming temperature. A satisfactory modelling of quasi-static and dynamic material behaviors is of great importance for understanding physical process and processes optimization. A dependence-based integrated methodology, together with an improved weighted multi-objective parameter identification strategy is presented for the development of phenomenological constitutive model and the parameter identification using experimental data from quasi-static and dynamic tests with instantaneous strain rate variations and plastic strain-related temperature changes. The improved multi-objective parameter identification model is reformulated by introducing three weighting factors for valuing different measure errors and fit standard errors in individual objective function corresponding to each test, considering the sampling point number and active material parameter number under different loading conditions, and balancing optimization opportunity of quasi-static and dynamic sub-objective functions. The methodology is verified for feasibility through illustrative constitutive identification for SiC_p/Al composites. This may provide a methodology of constitutive modelling for predicting material behaviors in quasi-static and dynamic modes equally well.     

Improved H2-generation performance of Pt/CdS photocatalyst by a dual-function TiO2 mediator for effective electron transfer and hole blocking

Surface modification with noble metal cocatalysts was proved to be a useful route for boosting photocatalytic efficiency of various photocatalysts. Nevertheless, considering the random dispersion of metallic cocatalysts on the photocatalyst surface, the noble metal-loaded photocatalyst generally shows a limited enhancement of its activity because the noble metals can also work as the recombination sites of photoinduced charges. In this paper, TiO₂ as a dual-function mediator (for effective electron transport and hole block) is successfully introduced into the interface of Pt and CdS to form PtTiO₂/CdS photocatalyst, with an aim of suppressing the high recombination rate of electron-hole pairs on the Pt active sites. Under visible light, all the prepared PtTiO₂/CdS displayed distinctly enhanced photocatalytic hydrogen-generation performance and the PtTiO₂/CdS(8%) attains the highest photocatalytic H₂-production rate (294.2?μmol/h), a value significantly higher than that of Pt/CdS about 3.2 time. A dual-function TiO₂-mediated mechanism was put forward to account for the superior hydrogen production of PtTiO₂/CdS photocatalyst, namely, the TiO₂ layer in the PtTiO₂/CdS not only works as electron-transport layers to effectively transfer photogenerated electrons to promote the H₂-production reaction on Pt cocatalysts, but also acts as hole-block layer to prevent the possible recombination of photogenerated charges on the Pt active sites, resulting in a distinct improvement of final H₂-generation activity.     

A novel ultra-high-temperature oxidation protective MoSi2-TaSi2 ceramic coating for tantalum substrate

To protect refractory metal against oxidation at ultra-high temperatures, a MoSi₂-TaSi₂ ceramic coating was prepared on a pure tantalum (Ta) substrate using a novel three-step process, which included dip-coating with a molybdenum slurry, vacuum sintering, and halide-activated pack cementation (HAPC). The original coating had a MoSi₂-TaSi₂ double-layer structure from the surface to the substrate. After oxidation at 1700°C for 8 h in air, the coating exhibited a complex multi-layer structure composed of SiO₂-Mo₅Si₃-MoSi₂-(Mo,Ta)₅Si₃-TaSi₂-Ta₅Si₃ from the outer layer to the inner layer, due to the high-temperature phase transition and diffusion of Si and O. The coating effectively protected the Ta substrate at 1700°C for 12 h without failure, thereby demonstrating great improvement to its service life in an ultra-high-temperature aerobic environment. The protective effect was attributed to the integrity of the ceramic coating and the formation of a dense, uniform SiO₂ film that effectively lowered the inward oxygen diffusion rate.     

Effect of SiC nanowires on the high-temperature microwave absorption properties of SiCf/SiC composites

SiC-nanowire-reinforced SiC_f/SiC composites were successfully fabricated through an in situ growth of SiC nanowires on SiC fibres via chemical vapour infiltration. The dielectric and microwave absorption properties of the composites were investigated within the frequency range of 8.2–12.4 GHz at 25–600 °C. The electric conductivity and complex permittivity of the composites displayed evident temperature-dependent behaviour and were enhanced with increasing temperature. The composites exhibited superior microwave absorption abilities with a minimum reflection loss value of ?47.5 dB at 11.4 GHz and an effective bandwidth of 2.8 GHz at 600 °C. Apart from the contribution of the interconnected SiC nanowire network and multiple reflections, the excellent microwave absorption performance was attributed to dielectric loss that originated from SiC nanowires with abundant stacking faults and heterostructure interfaces. Results suggested that the composites are promising candidates for high-temperature microwave absorbing materials.     

High-Q (Na1-xAgx)2WO4 (x = 0.1, 0.2) ceramics with ultra-low sintering temperature

The solid solution (Na_1-xAg_x)₂WO₄ (x = 0.1, 0.2) ceramics with ultra-low sintering temperatures were prepared by a modified solid-state reaction method. Through introducing Ag⁺ substitution at the Na⁺-site, the sintering temperature of the (Na_1-xAg_x)₂WO₄ ceramics have been lowered from 565℃ to 510–520℃, while their dielectric lose is still keeping low. The (Na_0.9Ag_0.1)₂WO₄ ceramic can be sintered well at 520℃ with a permittivity of 5.8, a Q × f value of 97 600 GHz and a temperature coefficient of ?70 ppm/℃ at 12.6 GHz. After being sintered at 510℃, the (Na_0.8Ag_0.2)₂WO₄ ceramic possesses the best properties with a permittivity of 6.1, a Q × f value of 70 600 GHz and a temperature coefficient of ?72 ppm/℃ at a frequency of 12.5 GHz. Due to the excellent dielectric properties, the (Na_1-xAg_x)₂WO₄ (x = 0.1, 0.2) ceramics are potential candidate for Low-Temperature Co-fired Ceramics (LTCC) applications.     

2-Ethyl-9,10-anthraquinone assisted sol–gel synthesis of Pd/γ-Al_2O_3 nanorods with enhanced catalytic performance in 2-ethyl-9,10-anthraquinone hydrogenation

A series of nanorod-like porous Pd/γ-Al_2 O_3 catalysts with controllable textural properties and enhanced catalytic performance in 2-ethyl-9,10-anthraquinone(eAQ) hydrogenation for H_2 O_2 preparation were successfully prepared via a facile sol-gel method using aluminum isopropoxide as aluminum precursor and eAQ as structure directing agent,sequential calcination and impregnation process with Na_2 PdCl_4 solution.The physicochemical properties of the catalysts obtained with different addition amounts of eAQ.were comparatively characterized by XRD,TG-DSC,BET,TEM,CO-TPR,H_2-TPR and H_2-O_2 titration.The results show that addition of eAQ can not only effectively control the textural properties(surface area,pore volume and average pore size) of the catalysts,but also lower their reduction temperature of active metal.Importantly,the catalyst obtained with an addition amount of 4 wt% eAQ shows the highest hydrogenation efficiency of 10.28 g·L~(-1),which is 37.3% higher than 7.49 g·L~(-1) of the catalyst obtained without eAQ.     

The potential of pervaporation for biofuel recovery from fermentation:An energy consumption point of view

Recovering alcohols from dilute fermentation broth is an emergent task in bio-fuel production process. Since they are primary planned for fuels, energy required to separate these alcohols should be considered in evaluating the potential of a separation technology. A membrane-based process, pervaporation, is of special interest because of its environmental friendliness and easy integrating character. This review probes into the fundamentals of pervaporation especially in terms of the heat required for evaporation. Meanwhile, the separation data of the most representative alcohol-selective pervaporation membranes reported in the literatures are collected and compared with the vapor–liquid equilibrium curve, which represents the distillation selectivity. They include:inorganic membranes, silicon rubber based membranes, Mixed Matrix Membranes and some other special materials. By doing so, the status of alcohol recovery via pervaporation would be more clear for researchers.For ethanol recovery, it is selectivity rather than flux that is in urgent need of solution. While for butanol recovery,membranes with satisfactory selectivity have been developed, increasing the separation capacity would be more pressing.