微乳凝胶固定化酶催化长链脂肪酸酯的合成

研究了以AOT(二 (2 乙基已基 )琥珀酸酯磺酸钠 ) /正庚烷 /水 /明胶组成的反相微乳凝胶固定化脂肪酶 ,在有机溶剂中催化棕榈酸和十六醇的酯化反应 .反应在 2 5℃下进行 ,固定化脂肪酶重复使用 16次后 ,平衡转化率仍可达 90 % .反应既可用釜式反应器又适用柱式反应器 .产物通过冷却的反应液后沉淀析出 ,回收率可达 6 5% ,产品纯度高 .     

Improve redox activity and cycling stability of the lithium-sulfur batteries via in situ formation of a sponge-like separator modification layer

The electronic nonconductivity of S and shuttle effect of soluble polysulfides are two fundamental issues that limit the application of lithium-sulfur (Li-S) batteries. Regarding these issues, herein, a sponge-like Ketjen black (KB)-triphenylphosphine sulfide (TPS) multifunctional modification layer was proposed to coat the separator of the advanced Li-S batteries. The layer was formed by an in situ spontaneous reaction between triphenylphosphine (TPP) of the conventional KB-TPP layer and Li₂S₆ solution. This functional layer can ensure a high e⁻ and Li⁺ conductivity while inhibiting the diffusion of soluble polysulfides. As a result, the redox activity, rate capability, and cycling stability of the batteries are significantly enhanced. Comparing with the discharge capacities at 2C for the PE separator, introducing the KB-TPS functional layer was beneficial for the capacity retentions of the cells, since the capacity increased from 16.1% to 66.6% at the same C-rate. A capacity degeneration rate of 0.045% per cycle was obtained for the cell with an S area density of 3.6 mg cm⁻². This work is a step forward in the exploration of advanced Li-S batteries, being a valuable reference for the study of related systems.     

Optimized formulation of an oxidative curing system for liquid polysulfide sealants used in fuel tanks by D‐optimal design method

In this work, the effective parameters in liquid polysulfide curing system were optimized by D ‐optimal design method. Five main components in the formulation, carbon black, vulcanizing agents (MnO₂, Na₂Cr₂O₇, and PbO₂), CaCO₃, fumed silica, and chlorinated paraffin, were selected. Mechanical and chemical properties of the samples were investigated. The results showed that tensile strength, hardness, viscosity, and optimum cure time (t₉₀) presented a suitable coordination with reduced quadratic model. For elongation at break and swelling tests, reduced two‐factor interaction (2FI), and for peel strength, a linear model showed the best correlation. To achieve the desirable properties for liquid polysulfide sealants used in fuel tanks, an optimized amount of the above components in the formulation were used. Finally, MnO₂ curing system, compared with Na₂Cr₂O₇ and PbO₂, was selected as the best choice. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

柱撑膨润土对染料酸性红B的吸附行为

在 [OH- ] /[Al3 ] =2 .4的反应条件下 ,利用Al3 与碱液反应制备出Keggin离子 ,并由此制备出了无机、无机 -有机柱撑膨润土 ;XRD -衍射数据表明 ,经柱撑后的膨润土层间距明显增大 ,达 1.9nm以上。研究了废水中染料酸性红B在 4种改性膨润土上的吸附行为 :经柱撑处理后的膨润土吸附能力明显大于钠基土 ,对酸性红B溶液有很高的脱色率和CODCr去除率 ,其吸附动力学行为遵循Bangham方程和Langmuir方程所述规律 ,平衡吸附量 qe 与平衡浓度Ce 间的关系符合Freundlich和Langmuir等温吸附方程 ,吸附表现为放热的物理吸附和有机质的分配作用。     

Electrochemical characterization of chemical species formed during the electrochemical treatment of chalcopyrite in sulfuric acid

The dissolution mechanism of chalcopyrite, and the potential range in which its passivation phenomenon takes place, were studied on carbon paste electrodes with chalcopyrite (99.46% purity, +300 mesh, 53 μm size) (CPE-CP) in 1.7 mol/dm³ H₂SO₄. A sequence of anodic potential pulses was applied to the CPE-CP to characterize its electrochemical behavior. Copper ions, dissolved by the potential pulses, were determined using a mercury film electrode (MFE) and the anodic stripping voltammetry (ASV) on a vitreous carbon disk. In addition, the modified surface of CPE-CP was characterized, before and after the potential pulses, by cyclic voltammetry (CV). The characterization of the final surface state of each electrochemically modified CPE-CP and the amount of dissolved copper showed five potential regions where the chalcopyrite dissolution mechanism changed. The initial dissolution occurs at 0.615 V ≤ E_anod < 1.015 V versus SHE forming a non-stoichiometric polysulfide (Cu_1−rFe_1−sS_2−t). The absence of copper ions in the solution indicates a passive sulfide. However, at 1.015 V ≤ E_anod < 1.085 V versus SHE, the passive product decomposes forming porous layers of non-stoichiometric polysulfide (Cu_1−xFe_1−yS_2−z) that allow the diffusional transport of charged species and the dissolution of the mineral. In the region of 1.085 V ≤ E_anod < 1.165 V versus SHE, formation covellite (CuS) was identified. At E > 1.165 V versus SHE, CuS is unstable and gives rise to complete dissolution of the chalcopyrite. Due to the experimental conditions, the mineral dissolution is inhibited by possible jarosite precipitation.     

有机膨润土制备及其对铬酸根离子吸附性能研究

用CTAB对膨润土进行改性,考察了有机土对铬酸根吸附的最佳条件,并对吸附铬酸根后膨润土的再生进行了研究。结果表明,在pH值为4～10的范围内,CTAB的用量为0.05∶1,改性时间1h,振荡吸附时间0.5h的条件下,对Cr(Ⅵ)的去除率可达74%;再生后的有机土基本恢复了对铬酸根离子的去除能力。     

水淬对金精矿焙砂中磁黄铁矿性质的影响

回转窑焙砂中的硫主要以磁黄铁矿形式存在，在高温及酸性气氛下直接水淬冷却时，磁黄铁矿的结构和性质发生了变化。ＤＴＡ－ＴＧ显示水淬焙砂在２３０℃有一明显的放热峰和失重，ＸＲＤ表明水淬焙砂中出现α－Ｓ的衍射峰，但经过３００℃焙烧后则消失。经２５０－３００℃二次焙烧后金的浸出率显著提高。初步研究结果认为磁黄铁矿受酸作用后表层形成了类似于多硫化物（如Ｓ＾２－２，Ｓ＾ｎ－ｎ，Ｓ＾（ｎ－１）ｎ＾－等）的缺铁性硫     

Selective Sorption of Mercury(II) from Aqueous Solution with an Organically Modified Clay and its Electroanalytical Application

Abstract

The organo‐clay used in this work was prepared from a Na‐montmorillonite (Wyoming‐USA deposit) by treatment with water solution of hexadecyltrimethylammonium cations. As organo‐clays exhibit strong sorptive capabilities for organic molecules, 2‐mercapto‐5‐amino‐1,3,4‐thiadiazole organofunctional groups, with potential usefulness in chemical analysis, were incorporated on its solid surface. The physically adsorbed reagent did not present any restrictions in coordinating with several metal ions on the surface. The resultant organo‐clay complex exhibited strong sorptive capability for removing mercury ions from water in which other metals and ions were also present. The purpose of this work is to study the selective separation of mercury(II) from aqueous solution using the organo‐clay complex, measured by batch and chromatographic column techniques, and its application as preconcentration agent in a chemically modified carbon paste electrode for determination of mercury(II) in aqueous solution.     

Tribological properties and tribochemical mechanism of lanthanum and boron compounds in oil

Lanthanum dialkyldithiophosphate (LaDDP) was synthesised. The tribological properties of a combination additive of LaDDP and an organo‐borate (OB) in oil were evaluated with a four‐ball test machine. The results show that the combination of LaDDP and OB gives better load‐carrying capacity and anti‐wear and friction‐reducing properties than the individual components. Rubbed surfaces after the friction tests were investigated using X‐ray photoelectron spectroscopy, Auger electron spectroscopy, and microhardness testing. The results indicate that a boundary film is composed of deposit films (including La₂O₃ and B₂O₃), chemical reaction films (including FeSO₄, FePO₄, and FeS), and a tribodiffusion layer (including La and B). Lanthanum can promote the decomposition of OB and the tribodiffusion of boron. From a mass spectroscopy analysis a tribochemical mechanism is suggested.