Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma

A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe²⁺ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH ₄ ⁺ , NO ₃ ⁻ and CO₂. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.     

Numerical analysis of amplification characteristic of erbium-doped waveguide amplifiers by FD-BPM

An efficient analysis method for erbium-doped optical waveguide amplifiers (EDWA) is presented. By solving the rate equation, the propagation in EDWA is stimulated using the finite difference beam propagation method (FD-BPM). The dependence of the gain of EDWA is investigated on the waveguide length, erbium concentration, and signal and pump power. The analysis shows that considerable gain levels, 3.35 dB/cm can be achieved in 10 cm-long EDWA with an erbium concentration of 2.0 × 10²⁶ ions/m³, signal power 1 W and pump power 100 mW at 980 nm.     

镁铝层状超分子化合物去除废水中的六价铬

实验比较了Na_2CO_3/Na OH、Na OH和NH4OH沉淀法制备的镁铝层状化合物对模拟废水中Cr(Ⅵ)的去除效果,并通过X射线衍射和Brunauer-Emmett-Teller(BET)方法分析了材料的结构特征。结果表明,以Na_2CO_3/Na OH为沉淀剂制备的镁铝层状化合物结晶度高、层状结构完整、比表面积较大、孔径适宜、吸附Cr(Ⅵ)的效果最佳,其优化吸附工艺为:固液比为1 g/500 m L,体系pH值为7~9,室温下震荡9 h。在最佳吸附条件下,镁铝层状化合物对Cr(Ⅵ)的饱和吸附量达到199.4 mg/g。镁铝层状化合物通过与含铬阴离子形成层状超分子化合物的方式实现了废水中铬的去除,对含Cr(Ⅵ)226.1 mg/L的实验室废水经6次工艺处理后,残余量小于0.5 mg/L,低于国家污水综合排放标准(GB8978-1996)指标。镁铝层状化合物是一种处理实验室废水中Cr(Ⅵ)的优良吸附剂。     

电子技术实验教学要注重学生综合能力的培养

电子技术实验是电子技术教学中的重要环节，因此如何开展电子技术实验以及在实验教学中怎样突出对学生综合能力的培养，一直是从事该学科教学的教师十分关心的问题。本文就这个问题进行了讨论。     

Octahedral tilting in MM'X4 metal-oxide organic layer structures

Three metal-oxide organic frameworks have been synthesized and characterized: vanadium 1,4-benzenedicarboxylate, V2O2F0.6(OH)1.4(BDC).0.4H 2O (1); indium 1,4-benzenedicarboxylate, In 2F2.2(OH)1.8(BDC).1.6H2O (2); and aluminum 1,4-benzenedicarboxylate Al2F3(OH)(BDC) (3). The three-dimensional structures of 1, 2, and 3 have the same framework topology as the previously reported vanadium (III) 1,4-benzenedicarboxylate, VIII2(OH)2F2(BDC). The frameworks consist of inorganic layers constructed from corner sharing ML 6 octahedra (M=V, In, Al and L=OH, F) linked by BDC ligands. The structures are related to a general class of perovskite-related layer structures with composition MM'X4. The layers show characteristic distortions that can be related to tilting of the ML 6 octahedra. In particular the structure of 1 consists of O-V distances that strongly alternate along the b axis. The electronic consequences of this distortion then create a tilting of the 1,4-benzenedicarboxylate ligand about the a axis. Crystal data: 1, orthorhombic, space group Pmna, a=7.101(2) A, b=3.8416(11) A, c=20.570(6) A; 2, orthorhombic, space group Cmcm, a=7.490(4) A, b=21.803(1) A, c=8.154(4) A; 3, monoclinic, space group P2(1)/m, a=10.7569(8) A, b=6.7615(3) A, c=7.1291(3) A, beta=76.02(1) degrees.     

Breathing and twisting: an investigation of framework deformation and guest packing in single crystals of a microporous vanadium benzenedicarboxylate

The structural details of the compounds vanadium benzenedicarboxylate VO(bdc)·Guest, where the Guests are the absorbed six-ring molecules: benzene, 1,4-cyclohexadiene, 1,3-cyclohexadiene, cyclohexene and cyclohexane, have been determined from single crystal X-ray data. All of the six-ring guest molecules show a high degree of ordering inside the channels of VO(bdc). The interactions between the guests and the host framework are dominated by van der Waals bonding. The six-ring molecules are all packed in two columns in the channels, either in herringbone or close to parallel patterns. The packing changes the space group symmetry of VO(bdc) from Pnma to the noncentrosymmetric space group P2(1)2(1)2(1). The VO(bdc) framework deforms to closely adapt to the shape and thickness changes of the double columns of the guest molecules. In addition to the well studied breathing deformation, a twisting deformation mechanism that involves a cooperative rotation of the octahedral chains accompanied by bending of the bdc ligand is apparent in the detailed structural data. More quantitative information on the remarkable flexibility of the VO(bdc) framework was obtained from ab initio calculations.