射流微泡曝气器溶氧性能测试与工程应用

射流微泡曝气器是一种基于新型微泡生成机理的曝气设备,具有广泛的工程应用价值。射流微泡曝气器溶氧性能测试分析的结果表明:当新设计的射流微泡曝气器进气量从0.2m3/h增至2.0m3/h时,其氧总转移系数从0.052L/min增加到0.338L/min,理论动力效率从0.659kg/kW·h增加到4.284kg/kW·h。与其他类型曝气器相比,该型射流微泡曝气器的氧总转移系数和理论动力效率均有显著提高。此外,射流微泡曝气器应用于实际工程中,废水出水水质中化学需氧量的平均去除率可达到76.6%。

基于CFD技术的机械搅拌通风发酵罐溶氧性能预测

以25℃的清水及空气为介质,应用两相流模型模拟发酵罐内流场的气、液两相流动。对模拟出的内流场,重点分析了气相含量、气相速度的分布情况。用取样实验进行气相含量验证,证明了应用CFD技术对机械通风发酵罐进行性能评价的有效性,为此类发酵罐性能预测评价提供了一种有效的技术手段。

Preparation of three-dimensional braided carbon fiber reinforced mullite composites from a sol with high solid content

To prepare the three-dimensional braided carbon fiber reinforced mullite （3D C/mullite） composites, an Al2O3-SiO2 solwith a solid content of 20% （mass fraction） and an Al2O3/SiO2 mass ratio of 2：1 was selected as the raw material. Characteristics andmullitization of the sol were analyzed throughly. It is found that the formation of mullite is basically completed at 1300℃ and thegel powders exhibit favorable sintering shrinkage. The 3D C/mullite composites without interfacial coating were fabricated throughthe route of vacuum impregnation-drying-heat treatment. Satisfied mechanical properties with a flexural strength of 241.2 MPa anda fracture toughness of 10.9 MPa·m1/2are obtained although the total porosity reaches 26.0%. Oxidation resistances of the compositesat 1200, 1400 and 1600 ℃ were investigated. Due to the further densification of matrix, the 3D C/mullite composites show tiny massloss and their mechanical properties are well retained after oxidation at 1600 ℃ for 30 min.

Study on Absorption and Regeneration Performance of Novel Hybrid Solutions for CO_2 Capture

Recently, a kind of hybrid solution MEA-methanol shows a better CO_2 capture performance over aqueous MEA solution. However, the vaporization of methanol is the biggest disadvantage that hinders its application, so it is necessary to minimize the vaporization of methanol during both the absorption and regeneration processes. In this work, two kinds of hybrid solutions were studied and compared with aqueous MEA solution and MEA-methanol solution, including MEA/TEA/methanol solution and MEA/glycerol/methanol solution. The absorption property of MEA/glycerol/methanol solution is better than aqueous MEA solution within a certain period of time and the absorption property of MEA/TEA/methanol solution is too poor to be used in CO_2 capture. By increasing the concentration of TEA and decreasing the concentration of MEA, the absorption rate, CO_2 capture efficiency and absorption capacity all decreased. Upon adding glycerol, the cyclic capacity decreased and the generation temperature increased, and moreover, the density and viscosity also increased considerably. So after adding TEA and glycerol, the CO_2 capture performance of MEAmethanol solvent cannot be improved.

Effect of sol size on nanofiltration performance of a sol-gel derived microporous zirconia membrane

This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off(MWCO) and salt retention of zirconia membranes derived from zirconia sols with different sizes were characterized. Thermal evolution, phase composition, microstructure and chemical stability of unsupported zirconia membranes(powder) were determined by thermogravimetric and differential thermal analysis, X-ray diffraction, nitrogen adsorption–desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly dependent on sol size. The sol with an average size of 3.8 nm, which is smaller than the pore size of the γ-Al2O3support(pore size: 5–6 nm), forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconia membrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconia membrane with a MWCO value of 1195 Da(pore size: 1.75 nm) and relative high retention rates towards Mg Cl2(76%) and Ca Cl2(64%) was successfully fabricated by dip-coating the sol with an appropriate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da(pore size: 2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide p H range of 1–12.

Selective oxidation of methanol to dimethoxymethane over V_2O_5/Ti O_2–Al_2O_3 catalysts

This paper describes the effect of the prepara- tion method of binary oxide supports （TiO2-Al2O3） on catalytic performance of V2O5/TiO2-Al2O3 catalysts for methanol selective oxidation to dimethoxymethane （DMM）. The TiO2-A1203 supports are synthesized by a number of methods including mechanical mixing, ball milling, precipitation, co-precipitation, and sol-gel method, which is followed by incipient wetness impregnation to produce V2O5/TiO2-Al2O3 catalysts. Among these samples, the V2O5/TiO2-Al2O3 catalyst prepared by the sol-gel method has the best catalytic performance with a maximum methanol conversion of 48.9 % and a high DMM selectivity of 89.9 % at 393 K, showing superior performance than V2O5/TiO2 and V2O5/Al2O3. The excellent catalytic performance of V2O5/TiO2-Al2O3 is attributed to the effective interaction between the active component and the mixed support. Such interaction changes the chemical states of supported active V components, produces an increased amount of V^4＋ species, and facilitates the electron transfer between support and active component. Additionally, the incorporation of titanium cation into the alumina structure could also help produce an appropriate amount of acidic sites, which increases the DMM selectivity. The coordinated environment of the dispersed vanadia on TiO2-Al2O3 mixed support improves the catalytic efficiency on methanol oxidation to DMM.

Improving the performance of inverted organic solar cells by adjusting the concentration of precursor solution of Al-doped ZnO

Al-doped ZnO(AZO) has been used as an electron transport and hole blocking buffer layer in inverted organic solar cells(IOSCs). In this paper, the AZO morphology, optical and structural properties and IOSCs performance are investigated as a function of precursor solution concentration from 0.1 mol/L to 1.0 mol/L. We demonstrate that the device with 0.1 mol/L precursor concentration of AZO buffer layers enhances the short-circuit current and the fill factor of IOSCs simultaneously. The resulting device shows that the power conversion efficiency is improved by 35.6% relative to that of the 1.0 mol/L device, due to the improved surface morphology and transmittance(300–400 nm) of AZO buffer layer.

Arbuscular mycorrhizal fungi protect a subtropical tree species exposed to simulated acid rain by accelerating photosynthetic ability,antioxidant enzymes and osmolyte accumulation

Acid rain(AR),which occurs frequently in southern China,negatively affects the growth of subtropical tree species.Arbuscular mycorrhizal fungi(AMF)mitigate the detrimental effects induced by AR.However,the mechanisms by which AMF protect Zelkova serrata,an economically important tree species in southern China,from AR stress remain unclear.We conducted a greenhouse experiment in which Z.serrata plants were inoculated with AMF species Rhizophagus intraradices and Diversispora versiformis,either alone or as a mixed culture,or with a sterilized inoculum(negative control).The plants were subjected to three levels of simulated sulfuric AR and nitric AR(pH 2.5,4.0 and 5.6)to examine any interactive effects on growth,photosynthetic capabilities,antioxidant enzymes,osmotic adjustment and soil enzymes.AR significantly decreased dry weight,chlorophyll content,net photosynthetic rate and soluble protein(SP)of non-mycorrhizal plants.Mycorrhizal inoculation,especially a combination of R.intraradices and D.versiformis,notably improved dry weight,photosynthetic capabilities,catalase,peroxidase,superoxide dismutase,SP and root acid phosphatase activity of Z.serrata under harsh AR stress.Moreover,the benefits from AMF symbionts depended on the identity of AM fungal species and the gradient of AR stress.Our results indicate that AM fungi protect z.serrata against AR stress by synchronously activating photosynthetic ability,antioxidant enzymes and osmolyte accumulation.These findings suggest that a combination of R.intraradices and D.versiformis may be a preferable choice for culturing Z.serratain southern China.

Secondary aerosol formation and oxidation capacity in photooxidation in the presence of Al_2O_3 seed particles and SO_2

To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NOx in homogeneous and heterogeneous reactions, a series of irradiated toluene/NOx/air and ?-pinene/NOx/air experiments were conducted in smog chambers in the absence or presence of Al2O3 seed particles. Various concentrations of NOx and volatile organic compounds(VOCs) were designed to simulate secondary aerosol formation under different scenarios for NOx. Under "VOC-limited" conditions, the increasing NOx concentration suppressed secondary aerosol formation, while the increasing toluene concentration not only contributed to the increase in secondary aerosol formation, but also led to the elevated oxidation degree for the organic aerosol. Sulfate formation was suppressed with the increasing NOx due to a decreased oxidation capacity of the photooxidation system. Secondary organic aerosol(SOA) formation also decreased with the presence of high concentration of NOx, because organo-peroxy radicals(RO2) react with NOx instead of with peroxy radicals(RO2 or HO2), resulting in the formation of volatile organic products. The increasing concentration of NOx enhanced the formation of sulfate, nitrate and SOA under "NOx-limited" conditions, in which the heterogeneous reactions played an important role. In the presence of Al2O3 seed particles, a synergetic promoting effect of mineral dust and NOx on secondary aerosol formation in heterogeneous reactions was observed in the photooxidation. This synergetic effect strengthened the positive relationship between NOx and secondary aerosol formation under "NOx-limited" conditions but weakened or even overturned the negative relationship between NOx and secondary aerosol formation under "VOC-limited" conditions. Sensitivity of secondary aerosol formation to NOx seemed different in homogeneous and heterogeneous reactions, and should be both taken into account in the sensitivity study. The sensitivity of secondary aerosol formation to NOx was further investigated under "winter-like" and NH3-rich conditions. No obvious difference for the sensitivity of secondary aerosol formation except nitrate to NOx was observed.

Facile synthesis of nickel cobalt selenide hollow nanospheres as efficient bifunctional electrocatalyst for rechargeable Zn-air battery

Designing high active,low cost and bifunctional electrocatalysts is urgent for developing clean energy storage and conversion systems.Transition metal selenides exhibit optimal electronic conductivity and tunable physicochemical properties,which endow them with potential for efficient electrocatalysts to facilitate the oxygen reduction and oxygen evolution reactions(ORR and OER).Herein,hollow NixCo0.85-xSe nanospheres were synthesized using a facile polyol based solution chemical method.The NixCo0.85-xSe exhibits an onset overpotential of 0.89 V for ORR,and an overpotential of 305 mV to achieve 10 mA cm^-2 for OER.Moreover,the NixCo0.85-xSe based Zn-air battery displays remarkable specific capacity and durability.Such superior catalytic performances can be attributed to the synergistic effect,large specific surface area and enhanced electron transfer rate.This approach provides a new way to design highly efficient bifunctional electrocatalysts for electrochemical energy storage and utilization.