无机化学实验中离子定性分析考核方法的研究

本文提出了一种针对化工类一年级本科生的元素无机化学实验离子鉴定部分的考核方法,介绍了从未知样的选择、测试题编写、考核过程实施的全过程,分析了考核结果,并从教学效果、可操作性、难易程度等方面讨论了这种考核方法的特点。     

Arsenate removal by zero valent iron: Batch and column tests

This study investigates the efficiency of zero valent iron (ZVI) to remove arsenate from water. Batch experiments were carried out to study the removal kinetics of arsenate under different pH values and in the presence of low and high concentrations of various anions (chloride, carbonate, nitrate, phosphate, sulphate and borate), manganese and dissolved organic matter. Borate and organic matter, particularly at higher concentrations, inhibited the removal of arsenic. Column tests were carried out to investigate the removal of arsenate from tap water under dynamic conditions. The concentrations of arsenic and iron as well as the pH and Eh were measured in treated water. Efficient removal of arsenate was observed resulting at concentrations below the limit of 10 μg/L in treated waters.     

表面活性剂吸附引起的硅石润湿性改变

用两相滴定法测定了十六烷基三甲基溴化铵(CTAB)和十二烷基苯磺酸钠(SDDBS)在水湿和油湿硅石(SiO_2)上的吸附量,考察了电解质和pH值对吸附量的影响,用Amott/USBM法测定了这两种表面活性剂引起的砂岩岩样润湿性改变。测定结果表明,阳离子活性剂比阴离子活性剂更容易吸附在水湿硅石表面,导致硅石水湿性明显减弱甚至变为油湿。无机电解质使阴离子活性剂在硅石上的吸附量显著增加,Ca~(2+)与阴离子活性剂间的络合作用有可能使硅石表面从水湿向油湿转化。pH值对CTAB和SDDBS在硅石上的吸附量有相反的影响。     

用氮离子注入40Cr钢表层改善机械性能的探讨

本文应用正交试验法,对氮离子注入40Cr 钢的表层,使物理、机械性能改变的机理作了分析。结果表明:氮离子注入剂量是影响表面显微硬度、磨损量和摩擦力的首要参数;注入能量是影响表面残余应力的首要参数。本实验正交分析所得最佳注入参数为:4×10~(17) ions·cm~(-2)剂量和100keV 能量.     

Preparation,characterization and photocatalytic activities of holmium-doped titanium dioxide nanoparticles

Holmium-doped TiO₂ nanoparticles with high photocatalytic activities were prepared by sol–gel method and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and surface area measurement by nitrogen adsorption in this study. Experimental results indicated holmium doping could increase the surface area of TiO₂ nanoparticles, and inhibit the growth of crystalline size and the anatase-to-rutile phase transformation. The results of photodegrading methyl orange showed holmium doping improved the photocatalytic activity of TiO₂, and the reasons could be attributed to the synergetic effects of large surface areas, small crystallite size, lattice distortion and more charge imbalance of holmium-doped TiO₂. In our experiment, the optimal doped amount was 0.3 mol.% for the maximum photocatalytic degradation ratio when holmium-doped TiO₂ was calcined at 500 °C, and the optimal calcined temperature was 600 °C when the doped amount was 0.5 mol.%.     

One-step synthesis of methylmethacrylate from methacrolein over Keggin-type heteropoly compounds

One-step synthesis of methylmethacrylate (MMA) using heteropoly compounds (HPCs) as catalysts was demonstrated by feeding a mixture of methacrolein (MAL), air, water, nitrogen and MeOH (methanol). The HPCs with different counter-ions, such as H_1.7Cs_1.5Cu_0.25As_0.1PMo₁₁VO₄₀ (CsPMo₁₁VO₄₀), H_1.7La_0.7Cu_0.25As_0.1PMo₁₁VO₄₀ (LaPMo₁₁VO₄₀) and H_1.7K_1.5Cu_0.25As_0.1PMo₁₁VO₄₀ (KPMo₁₁VO₄₀), were studied in oxidation of MAL, esterification of methacrylic acid (MAA) and one-step synthesis of MMA from MAL, respectively. The selectivity of MAA was up to 45.7% and MMA was 44.6% with 93.3% MAL conversion over CsPMo₁₁VO₄₀.     

Chemical evaluation of cement-based sandcrete wall deterioration

Cement-based structure stability could be characterized not only by their mechanical strength, soil geophysics and loading condition, but also the resistance to various physical and chemical factors that could initiate its corrosion. The contribution of water and various water-based solutions in the environment, to cement-based structure durability could be either physical as in seasonal flooding of the structure or chemical often initiated by the presence in the solution of organic or inorganic compounds or gases. Irrespective of the corrosion type, its destructive effect could be attributed to the build up of internal stress and weakening of the structure matrix. This work is aimed at investigating the role of chemical changes in the sandcrete matrix in the formation and development of macrocracks in cement-based sandcrete walls. Collected sandcrete samples were analyzed using titrimetric and granulometeric methods. Results showed that the percentage composition between the top and bottom of SiO₂ was high in all the sandcrete blocks samples analyzed ranging from 76.72% to 80.30%. This indicates high permeability of ground level structure. The acidic nature of the soil in some area varying from pH = 5.89-6.11 could seriously undermine the structures strength. The percentage compositions of CaO were generally very low ranging from 3.83% at the ground to 4.44% at the top levels. For most points there were percentage compositional differential across cracked points horizontally and vertically. This is an indication of either poor cement quality or non-compliance to standards' requirements. There is a need to develop a model equation for the migration of minerals' hydrates in sandcrete wall.     

Fabrication of nanoporous Si electrocathode by high-energy argon ion irradiation for improved electrocatalytic hydrogen production

Developing a cost-effective material to replace Pt catalysts for hydrogen evolution reaction (HER) holds great promising for clean energy technologies. In this work, we developed a simple way to prepare nanoporous Si by argon ion irradiation at 90 keV to fluences of 0.5, 1, 2 × 10¹⁷ ions/cm². After post-irradiation annealing at 700 °C in vacuum (2 × 10^?4 pa) for 5 h, the nanoporous Si was formed which displays largely enhanced electrocatalytic water splitting compared with the unirradiated Si. We also investigated the influence of fluence on morphology and the HER performance of the electrocathodes. It was found that 1 × 10¹⁷ Ar⁺ ions/cm² irradiated Si showed the highest HER performance. The largely enhanced HER activity comes from the unique morphology which results by Ar⁺ ions irradiation and post-irradiation annealing. We further fabricated electrocathodes by coating Ni film on the nanoporous Si, significant improvement of the HER performance compared with Ni coated planar Si was found. Using the ion irradiation technology, we developed a new method to fabricate electrocathode with large specific surface area for largely enhanced hydrogen evolution reaction activities.     

影响锆冻胶成冻因素的研究

本文研究的锆冻胶是聚丙烯酰胺(PAM)由氧氯化锆(ZrOCl2)形成的锆的多核羟桥络离子交联而成的.研究了PAM溶液的pH值、ZrOCl2的质量分数、PAM的质量分数、温度、水解度、相对分子质量、矿化度等因素对锆冻胶的成冻时间和冻胶强度的影响.成冻时间和冻胶强度分别由转子旋转法和突破真空度法测定.研究结果表明在实验条件范围内,温度越高,PAM和ZrOCl2的质量分数越大,水解度越低,相对分子质量越高,则锆冻胶的成冻时间均越短;而对于pH值及矿化度,则存在最佳成冻范围,即pH值为4-6,矿化度为8×103-4×104mgL-1时成冻时间最短.研究还证实,锆冻胶的成冻时间与冻胶强度的关系符合一般冻胶所遵循的规律,即成冻时间越短,冻胶的强度越高.锆冻胶在调剖堵水、酸化压裂、防砂等方面有重要的应用.