Polyethyleneimine/activated carbon paper-based material for low-concentration hexavalent chromium removal

Activated carbon paper-based materials were prepared from softwood pulp, activated carbon powder, and polyester fiber through wet forming process. Then polyethyleneimine was loaded on the activated carbon paper-based materials using physical impregnation method to fabricate green, low cost, and degradable PEI/activated carbon composite paper-based adsorbent materials (PPCA) for the removal of Cr(VI) from drinking water. The surface characteristics of the adsorbent were analyzed by SEM, EDX, BET, FT-IR, and XPS. It was found that the maximum adsorption capacity of Cr(VI) could reach up to 1.58 mg g^?1 when the PEI immersion concentration is 1%, the contact time is 180 min, the temperature is 30 °C and pH?=?2. The adsorption of Cr(VI) on PPCA conformed to both the freundlich isotherm model and the quasi-second-order kinetic model, indicating that the adsorption was multi-molecular layer adsorption controlled by chemical reaction process. The adsorption mechanism of Cr(VI) on PPCA included electrostatic attraction, redox and chelation. Overall, this study provides a green, large-scalable production way for the preparation of biodegradable adsorption materials for the efficient removal of Cr(VI) from drinking water aiding the safe management of aqueous system.

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1-(2,3,4-Trihydroxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid as reagent for spectrophotometric determination of boron in plants

A highly sensitive and selective method has been developed for spectrophotometric determination of boron in plants, the method based on the color reaction of new reagent 1-(2,3,4-trihydroxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid (THBA) with boron (III). In an ammonium acetate solution of pH 8.0, boron(III) reacts with THBA to form a 1:2 yellow complex which has a maximum absorption peak at 430 nm. The reaction can complete within 90 min and the absorbance of the complex remains maximum and almost constant at least for 24 h under a temperature range from 0 to 35 °C. The apparent molar absorptivity and Sandell's sensitivity are 2.95 × 10⁴ l mol⁻¹ cm⁻¹ and 0.00036 ng cm⁻², respectively. The limit of quantification, limit of detection and relative standard deviations were found to be 5.1, 1.5 ng ml⁻¹ and 1.12%, respectively. Under the optimum conditions, the absorbency of the complex (λ_max = 430 nm) increases linearly with concentration up to 0.8 μg ml⁻¹ of boron(III). The influences of foreign ions on the determination of boron were investigated in detail. Most of foreign ions can be tolerated in considerable amounts. Experiments have indicated that THBA as chromogenic reagent for spectrophotometric determination of boron has excellent analytical characteristics. Its sensitivity is more than 4.2-fold that of azomethine-H, and stability is advantage over other derivatives of azomehine-H remarkably. Moreover, the synthesis of THBA and its physicochemical properties of THBA were also investigated in detail. Proposed method has been applied to the determination of boron in plants with satisfactory results.     

Regulation of Strong Metal-Support Interaction by Alkaline Earth Metal Salts

Classical strong metal-support interaction (SMSI) is of significant importance to heterogeneous catalysis, where electronic promotion and encapsulation of noble metal by reducible support are two main intrinsic properties of SMSI. However, the excessive encapsulation will inevitably hamper the contact between active sites and reactant, leading to reduced activity in catalysis. Herein, alkaline earth metal salts are employed to depress the encapsulation of Ru nanoparticles in Ru/TiO₂ catalyst in the present study. Thermodynamic calculation, transmission electron microscopy (TEM) and chemisorption results show that the alkaline earth metal salts could successfully prevent the migration of TiO_2-x overlayer to Ru nanoparticles in Ru/TiO₂ catalyst via in situ formation of titanates, resulting in high exposure of active metal. Meanwhile, X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H₂-TPR) results reveal that an even stronger electron donation from the reduced support to Ru nanoparticles is achieved. As a result, the alkaline earth metal salts-doped Ru/TiO₂ catalysts exhibit superior activity in catalytic hydrogenation of aromatics, which is in contrast to the pristine Ru/TiO₂ catalyst that shows negligible activity under the same conditions due to the excess encapsulation of Ru nanoparticles in Ru/TiO₂ catalyst.     

剪刀式尾桨涡流干扰机理和气动特性研究

采用非常规剪刀式尾桨对直升机整体性能有着重要影响,关于其复杂流动干扰机理的研究尚处在发展之中. 为了掌握剪刀式尾桨的流动干扰机理和参数影响规律,建立了适合于悬停状态下剪刀式尾桨干扰涡流场分析的计算流体力学(computational fluid dynamics, CFD) 数值模拟方法. 采用积分形式的Reynolds-averagedNavier-Stokes (RANS) 方程作为旋翼流场求解控制方程,围绕旋翼流场的结构网格采用嵌套网格方法生成. 在CFD 方法验证基础之上,对悬停状态下两种不同构型剪刀式尾桨桨尖涡的涡核位置和强度的演变规律进行了定量分析,并对流场中桨尖涡与桨叶的贴近干扰、碰撞、破碎运动,同时准确捕捉了不同尺度涡之间的相互干扰、融合的过程进行了分析. 进一步研究了剪刀角和轴间距参数对不同构型剪刀式尾桨气动特性的影响规律. 计算结果表明,剪刀式尾桨流场中存在复杂的桨-涡干扰和涡-涡干扰现象,剪刀角和轴间距对剪刀式尾桨的气动特性有重要影响,L 构型剪刀式尾桨气动性能整体优于U 构型剪刀式尾桨.      

离子交换树脂层析法分离木糖醇结晶母液

研究了001系列离子交换树脂抗衡阳离子型式、树脂交联度、树脂粒径等因素对木糖醇结晶母液分离为糖组分和糖醇组分的影响.筛选出了具有较好分离效果的 001×8(Ca)(0.15mm～0.30mm)树脂.对柱温、柱长径比、进料量、进料浓度、洗脱速度、洗脱液pH等操作因素进行了分离条件优化.在优化条件下,对未糖醇结晶母液进行分离,得到去除糖组分的糖醇组分回收率为92.3%,完成了木糖醇结晶母液的阶段性分离纯化任务.     

Plane problems in piezoelectric media with elliptic inclusion

I.IntroductionPiezoelectricmedia,asa"ex\'typeoffullctionalmaterial.arex'idel}'appliedtomanytechnologicalfieldsduetoitselectronlechallicalcouplillgeffect.Defects.likethatofothermaterials.arenotlimitedtocracks.x'oidsandinclusionsillpiezoelectricmaterialsorelements.Yet,stressconcentrationsornoll-ullitbrllldistl-ibutionsofelectricfieldillducedbythosedefectsareoneofthehe}l'filctorswllicllwouldleadpiezoelectricstructurestonon-normalfailure.Therel'ore.itisofgrealimportancetostudythepropertiesofthos…     

制备色谱分离糖醇中的超载状态表征

以蔗糖、葡萄糖为表征物,研究了在不同超载方式和超载程度时,糖醇在制备色谱(PLC)上的分离行为及各柱分离参数的变化规律。结果表明,单组分体积超载可用理论塔板数N、峰宽W进行描述,浓度超载用N、拖尾因子Tf进行描述;双组分超载方式用N、分离度Rs等柱分离参数进行描述。提出了一种以N作为超载的通用表征参数,Tf、W和Rs分别为比较好的表达单组分浓度超载、体积超载和双组分超载点表征参数的超载表征方法。通过上述参数分析得到蔗糖、葡萄糖的单组分浓度超载点分别为150,200 g/L ;双组分混合样品受彼此     

衬底温度对ZnO薄膜晶体结构和电学性质的影响研究

ZnO films were deposited on glass substrates by gas discharge reaction evaporation. The influences of substrate temperature on the surface morphology, crystal structure and electric properties of ZnO films were studied by scanning electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy and complex impedance spectroscopy. The results show that the films with dense and amorphous structure and lower grain boundary resistance were deposited at room temperature. When the substrate temperature is higher than 50 ℃, the films with certain c-axis orientation can be deposited. With the increase of the substrate temperature, the preferential orientation of ZnO films along c-axis is augmented, the tensile stress along c-axis orientation decreases and the grain boundary resistance increases in a marked degree. When the substrate temperature is higher than 100 ℃, the increasing trend of the preferential orientation of ZnO films along c-axis slows down. ZnO films possess high preferential c-axis orientation and best crystalline quality at 180-200 ℃. These possess a smooth surface, symmetrical grain dimension (i.e. 30-40 nm), inerratic crystal shape, less tensile stress and 0.965 epitaxial degree along the c-axis direction. Here the grain boundary effect increases and the grain boundary resistance is evidently more than that of the films deposited at room temperature. The mechanism by which substrate temperature affects crystal structure and grain boundary properties were also discussed.     

Theoretical studies on the structures and isomerization of the LiSiF_3 system

Various possible isomers of LiSiF_3 system and isomerization between them have been studied at G2(MP2) level using ab initio calculations. The relative energies of four minimum points on the potential energy surface are -128.6, -194.3, -12.7 and -122.8 kJ/mol (taking the sum of the energies of LiF and SiF_2 as zero) . The structural energy of the four-membered ring that contains three F-Si-F-Li four-membered rings with C_(3v) symmetry is the lowest. The highest potential barrier for the isomerization of the remaining three-or four-membered structure is 12.5 kJ/mol.     

制备色谱分离技术的现状和发展

本文介绍了近年来生物和化工领域在开发具有高吸脱附、低返混性能,能直接处理含颗粒料液、连续操作、易放大和建造等特性的色谱工艺技术,尤其是柱色谱工艺技术方面的发展情况,以及这些工艺技术在制备和工业规模上的应用,并对各类色谱新工艺技术在使用中的优缺点进行了讨论。