锗烟尘中锗浸出过程动力学研究

本文对锗烟尘中锗浸出过程的动力学和反应机制进行了研究.结果表明,锗烟尘浸出符合不生成固体产物层的"未反应核缩减型"模型,动力学方程遵从1-2a/3-(1-a)1/3=kt.锗烟尘中锗浸出的表观活化能12.603kJ/mol,这表明锗烟尘中锗的浸出过程为边界层扩散所控制.在浸出时间3小时内,锗的浸出反应为2级反应.提高酸的浓度、温度、搅拌强度均可加速锌浸出速度,提高浸出率.     

氯离子对硫化矿发电浸出过程影响的机理研究

采用双电池体系综合考虑了Cl-对硫化矿的FeCl3浸出过程的影响.研究结果表明,Cl-对所研究各硫化矿发电浸出的影响效果类似:阳极电解液中Cl-直接参与硫化矿发电浸出过程.发电输出功率随着Cl-浓度的增加而增加,但是浓度增大到一定程度时,其影响作用减弱.本研究对各矿物提出了相应的反应机理,建立了各体系发电浸出速率与[Cl-]的动力学关系,对镍精矿、铜精矿、闪锌矿及方铅矿体系分别为:模型与实验结果吻合.     

铁离子对硫化矿发电浸出过程影响的机理研究

本研究采用双电池体系考察了铁离子对硫化矿的FeCl3浸出过程的影响.研究结果表明,Fe3 对所研究各硫化矿发电浸出的影响效果类似:阴极电解液中Fe3*仅在较低的FeCl3浓度范围内(<0.1～0.2 mol L1)对发电浸出速率有显著影响.对各矿物提出了相应的反应机理,建立了各体系发电浸出速率与[Fe3 ]的动力学关系,对镍精矿、铜精矿、闪锌矿及方铅矿体系分别为:模型与实验结果吻合.     

富镧稀土镍储氢合金催化甲苯液相加氢反应的动力学研究

研究了由富镧稀土镍储氢合金与甲苯组成浆液储氢体系 ,储氢合金催化甲苯液相加氢反应的动力学特性。考察了反应温度、液相氢浓度等因素对浆液体系内部传质 反应过程的影响。结果表明 ,在实验条件下富镧稀土镍 甲苯浆液体系中甲苯的液相加氢反应速率随反应温度的升高而升高 ,并在 4 90K左右达到最大 ,当温度超过 5 10K后反应速率迅速下降。富镧稀土镍 甲苯浆液体系中甲苯的液相加氢反应为反应控制过程 ,体系中气 液界面和液相主体到催化剂表面的传质阻力完全可以忽略。表现反应速率对甲苯表现为零级 ,对液相氢浓度为一级 ,得到反应动力学模型 ,该模型与实验结果有很好的一致性 ,富镧稀土镍催化的甲苯加氢反应的活化能为 4 1 0 1kJ·mol- 1。     

常压盐酸浸出红土镍矿的工艺条件优化

为有效提取红土镍矿中镍资源,为工业化生产提供依据,本文作者经过一系列的实验研究,在250r/min搅拌转速下,采用粒度为0.105mm的矿粉,得出如下最佳实验室常压盐酸浸出工艺条件:盐酸初始浓度9.0mol/L,固液比1∶2.00(矿粉用量不少于250g),保温条件下反应时间30min,在该最佳实验条件下镍的平均浸出率为97.68%.     

还原焙烧红土矿的硫酸浸出动力学

研究了选择性还原焙烧红土矿的硫酸浸出动力学.实验考察了浸出温度(30 ℃～70 ℃)和硫酸浓度(0.01～0.5 mol·l-1)对Ni、Fe浸出率的影响.结果表明:红土矿的选择性还原焙烧可增快Ni的浸出而抑止Fe的溶解.Ni的浸出动力学可用Avrami方程描述,其浸出反应的表观活化能为(15.40±0.18) kJ·moL-1.Fe的浸出受内扩散过程控制,浸出的表观活化能为(55.16±1.37) kJ·moL-1.     

加氢精制催化剂的状态对吡啶加氢脱氮活性的影响

发现在同样反应条件下,各种不同类型的加氢精制催化剂还原态比硫化态的吡啶加氢脱氮活性要高得多,某些催化剂的吡啶脱氮率甚至要高出一个数量级以上。通过研究Ni/Ni+W原子比与硫化态和还原态NiO-WO_3/Al_2O_3催化剂吡啶加氢脱氮活性的关系,可以清楚地看出:在硫化态催化剂中钨的硫化物是主要活性组份,而镍的硫化物是助剂;另一方面,在还原态催化剂中主要活性物质是镍。通过对吡啶加氢脱氮反应机理的分析,认识到金属Ni和金属Co不仅具有很高的加氢功能,对氮己环中的C-N键断裂也具有很高的氢解功能。用热重法对NiO-WO_3/Al_2O_3催化剂体系进行还原动力学研究的结果表明:催化剂的还原度和初始还原活化能与吡啶加氢脱氮活性之间有很好的对应关系。对催化剂还原过程的动力学数据分别用Elovich方程和核增长模型进行数据处理,结果表明,Elovich方程能更好地反映催化剂还原的动力学特征。     

两步酸浸法提高铈和铽浸出率的工艺研究

为了提高废弃荧光粉中Ce~(4+)和Tb~(3+)的浸出率,采用两步酸浸法。研究了助浸剂对蓝粉和绿粉的镁铝尖晶石结构的破坏作用,不同酸浸工艺参数对Ce和Tb浸出率的影响;对添加助浸剂后的酸浸反应动力学进行研究,并采用阿伦尼乌斯方程计算酸浸反应活化能。结果表明:不同助浸剂对尖晶石结构破坏作用不同,质量比为1∶0.8的柠檬酸钠作为助浸剂效果最优。酸浸工艺参数对Ce~(4+)和Tb~(3+)的浸出率具有重要的影响,最优工艺:HNO_3的浓度为2 mol·L~(-1),浸出温度60℃,浸出时间为2 h,反应转速300 r·min~(-1)。在最优工艺和质量比为1∶0.8的柠檬酸钠作为助浸剂的条件下,Ce~(4+)和Tb~(3+)浸出率分别达到了98.88%和97.12%。通过建立酸浸反应动力学模型和计算酸浸反应活化能,得到了加入助浸剂的浸出过程受扩散控制。     

CO2矿化反应基础研究 I.镁橄榄石和蛇纹石盐酸浸出动力学研究

对盐酸浸取镁橄榄石和蛇纹石的过程进行了研究,考察了酸浓度、浸取温度对镁浸出率的影响。结果表明,提高酸浓度和浸取反应温度能够提高镁橄榄石和蛇纹石中镁的浸出率。采用单粒级矿物原料浸出实验获得的动力学数据,利用收缩核模型分析了橄榄石和蛇纹石的镁浸出过程动力学,镁橄榄石浸出动力学属表面化学反应控制,而蛇纹石浸出反应为产物层扩散控制。两种矿物结构的差异影响镁浸出的难易程度,也决定了不同的浸出动力学行为。     

生物浸出回收废弃镍-镉电池研究

在中国,只有不到1%的废弃干电池被回收,因此有必要寻找一种既经济、快速,又利于环保的处理废弃干电池方法.生物浸出是回收废弃干电池有毒金属效果最好的方法之一.本研究应用本地下水道废水经驯化培养后产生的酸性废水作浸出菌种,考察pH值、生化反应器污水停留时间(RTB)、浸取时间、生化反应液是否添加Fe粉等实验条件对废弃镍-镉电池镍、镉浸出率的影响.结果表明,在pH值1.8~2.1、RTB 5 d、浸取时间50 d、生化反应液添加Fe粉条件下,可使镍-镉电池中镍、镉浸出率分别达到87.6%和86.4%,从而为工业生产提供了科学依据.     

国内光催化研究进展简述

分1975~1985, 1985~1995和1995~2012三个时期简要介绍了国内光催化研究进展, 主要侧重于光催化材料及其改性、应用和反应机理方面的研究进展, 并指出了当前光催化领域存在的一些重要问题和未来的发展趋势, 涉及到光解水、CO₂还原、环境净化和选择性有机合成等方面.     

青蒿素研究进展

青蒿素是目前治疗疟疾的特效药。本文对自青蒿素发现以来的最新研究进展进行了比较详尽的综述。内容包括: 青蒿素的发现及历史, 青蒿素的来源, 青蒿素的全合成,青蒿素的生物合成, 青蒿素衍生物以及植物组织培养生产青蒿素。     

Reactions in droplets in microfluidic channels

Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights.     

Recent Advances in Analytical Methodology for in vivo Electrochemistry in Mammals

Electrochemistry is one of the most advanced techniques for monitoring neurochemical activities in the living brain because electrochemical approaches bear the advantageous features of high spatial and temporal resolutions, which facilitate its tremendous potential in investigating the highly spatially heterogeneous brain system and the fast dynamics of neurochemical activities. On the other hand, since brain is the most complicated organ in the sense of its numerous kinds of neurochemical species, high selectivity is always required for any analytical methods that approach the brain. In this review, we will discuss various electrochemical methodologies to achieve selective detection of neurochemicals in mammalian brain and the strategies developed mainly by our group towards selective monitoring of both electrochemically active and inactive neurochemicals. At the end, we will discuss possible solutions towards brain mapping of neurochemical species and combination of neurochemical detection strategy with electrophysiology as the direction of future development of electroanalysis in living brain.     

Interpretation of inorganic arsenic metabolism in humans in the light of observations made in vitro and in vivo in the rat

The toxicity of inorganic trivalent arsenic for living organisms is reduced by in vivo methylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (As_i). In order to document the methylation process in humans, the kinetics of As_i, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of As_i. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As₂O₃) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterized in vitro and in vivo in rats as follows: (1) production of As_i metabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S-adenosylmethionine), lead to the production of mono- and di-methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of As_i uptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic systems.     

乙基香兰素研究前景

报导了近几十年来国内外关于乙基香兰素的研究进展与动态,并简单介绍了本文作者在该方面所取得的研究成果,参考文献33篇。     

Gemini表面活性剂合成进展

系统总结了近百种Gemini表面活性剂的合成路线和方法,并且按照其结构特点分门别类地进行比较和归纳,对今后Gemini表面活性剂的合成发展方向提出了一些看法,这对促进此类新颖表面活性剂的工业化进程将具有指导意义。     

Trends in education in analytical chemistry

Summary At the session of the WPAC of Fechem on education in analytical chemistry it was concluded that it is now essential to include chemometrics and basic knowledge of computers in all courses on analytical chemistry.

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Tendenzen in der analytisch-chemischen Ausbildung

Zusammenfassung Bei einer Tagung der WPAC über die Lehre auf dem Gebiet der analytischen Chemie wurde bei der Betrachtung neuer Aspekte festgestellt, daß vor allem Chemometrie und Grundkenntnisse in Computertechnik in die Ausbildung aufgenommen werden sollten.

     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

AGET ATRP in the Presence of Air in Miniemulsion and in Bulk

Summary: The recently developed initiation system, activators generated by electron transfer (AGET), is used in atom transfer radical polymerization (ATRP) in the presence of a limited amount of air. Ascorbic acid and tin(II ) 2‐ethylhexanoate are used as reducing agents in miniemulsion and bulk, respectively. An excess of reducing agent consumes the oxygen present in the system and, therefore, provides a deoxygenated environment for ATRP. ATRP of butyl acrylate is successfully carried out in miniemulsion and in the presence of air. During polymerization the radical concentration remains constant. The polymerization reaches over 60% monomer conversion after 6 h, which results in polymers with a predetermined molecular weight = 14 000 g · mol⁻¹ and a low polydispersity ( = 1.23). AGET ATRP of styrene is also successful in bulk in the presence of air, as evidenced by linear semi‐logarithmic kinetics, which leads to polystyrene with an of 13 400 g · mol⁻¹ and a low polydispersity index ( = 1.14).

Appearance of miniemulsion before and after the reducing agent ascorbic acid was added (left); and GPC traces representing molecular weights during the AGET ATRP of BA in miniemulsion in the presence of air (right).