Chemical Relaxation of Surface Reactions

The study of the rate of self-adjustment of a homogeneous, chemically reacting system that has been perturbed from its thermostatic equilibrium has received much attention recently, and has been very fruitful in unraveling the details of the molecular encounters underlying chemical changes. Of singular interest has been the study     

Theory of Ion Exchange and Development of Charge in Kaolinite-Water Systems

Crystal-chemical concepts applied to cation adsorption on kaolinite crystals in a water medium permit the calculation of bond energies. These values place the cations in the proper sequence of replacing power. Comparison of bond energies with thermal energy makes possible the calculation of charge on the particle and explains much of the observed behavior of kaolin-water systems.     

离子交换玻璃表面性质研究

针对离子交换增强玻璃稳定性问题,详细研究了由钾离子作为增强离子的玻璃表面性质.利用光学显微镜观察玻璃表面在加速风化条件下表面被侵蚀的情况,并用原子吸收光谱(AAS)研究玻璃在该加速风化条件下,表面K+偏析的情况.通过场发射扫描电子显微镜(FEGSEM)测试K+离子交换深度,用X射线光电子能谱(XPS)研究玻璃在离子交换前后表面元素含量的变化.研究表明,在加速风化条件下,离子交换增强玻璃表面较普通玻璃更容易受到侵蚀,K+离子向表面偏析明显.研究发现造成此种现象的原因是:在交换过程中,处于KNO3电解质中的玻璃表面吸附一层K+离子,形成Sterm紧密层,由于Stern层的距离只有几纳米,玻璃表面对K+的吸附力非常大,离开溶液后,表面层的活性大量K+离子依旧存在玻璃表面,致使离子交换玻璃表面稳定性降低.     

Ion Beam Induced Charge characterization of epitaxial single crystal CVD diamond

IBIC (Ion Beam Induced Charge) technique has been used in order to characterize single crystal epitaxial CVD diamond film with respect to homogeneity and stability of the response (in terms of charge collection efficiency, cce) as a function both of counting rate and of the number of counts per unit surface area. The maximum shift of cce peak, under a 1.2 MeV proton microbeam, is 1.5% for counting rates from 43 to 4330 Hz, while the homogeneity, evaluated as the standard deviation with respect to the average value of cce over strip-like regions 60–100 μm wide and 800–1200 μm long, is 0.5%. Counting rates per unit surface area were between 30 and about 15,000 Hz/mm². A total number of counts per unit area up to 9 10⁶ counts/mm² was reached without noticing any polarization effect due to trapped charge. Moreover, the functionality of a new kind of bulk electrode, realized by a boron doped buffer layer laterally contacted with Ag paste, has been checked by measuring cce at different proton ranges.     

化学沉淀法处理离子交换含盐废水试验

在原有的离子交换系统中增加一个回收系统,分步沉淀处理后去除废水中大部分的钙镁离子,清液作为再生剂回用的同时得到钙盐镁盐2种副产品。低含盐废水可静置澄清后回用作清水,试验了各种工艺条件的影响。结果表明,以NaOH为主剂的沉淀剂A进行第1步沉淀,沉淀分离后再投加以Na2CO3为主剂的沉淀剂B进行第2步沉淀,对硬度离子的去除效果更好;使用回用的再生剂处理树脂后生产的软化水在一定时间内没有检测出硬度离子;所得CaCO3的质量分数为97-2％纯度较高,可作为化工原料出售;浓盐废水作为再生剂回用前先要补充氯化钠,并用盐酸中和处理。     

离子交换树脂对铜离子吸附交换行为的研究

采用335弱碱性阴离子交换树脂交换吸附酞菁绿废水中高含量的铜离子。研究结果表明,335OH型树脂的交换吸附和脱附性能均优于701Cl,701OH及335Cl树脂,其干树脂的静态吸附交换容量大于120mg/g,工作交换吸附容量43.68mg/g,单柱20BV时铜的去除率可达93%以上,双柱串联处理60BV的去除率在99.91%以上,可确保出水中铜含量达到国家二级排放标准。选用8%HCl溶液为脱附剂,脱附率大于95%,从脱附液中可回收氧化铜,从而实现资源化的目的。树脂经再生后可重复使用,性能稳定,具有良好的应用前景。     

PPE的化学改性及在离子交换膜中的应用

介绍了聚苯醚(PPE)在化学改性方面的研究进展,简述了各种封端剂对低分子量PPE进行封端改性,重点描述了使用溴化、磺化等对PPE功能化改性,指出了目前将PPE由热塑性树脂向热固性树脂改性的发展方向,并对改性的PPE在阴离子交换膜中的应用进行了总结,得出了控制好吸水率、离子交换能力与力学性能的平衡是制备阴离子膜的关键.分...     

离子交换对磷酸盐玻璃表面裂纹扩展的影响

采用LiNO3和NaNO3混合熔盐在250℃对N31型磷酸盐玻璃表面进行离子交换处理,研究了小离子交换大离子对玻璃表面和亚表面裂纹的扩张作用.利用偏光显微镜、扫描电子显微镜、能谱仪对离子交换前后玻璃表面形貌和成分进行了测试,根据有限源扩散动力学和离子交换表面应力分布理论,分析了离子交换时间和H2O对裂纹扩张的影响.结果...     

Longxing Chemical Profit Decreased Due to Economic Situation

Recently, Zhongding Holding successfully acquired Germany KACO company engaged in producing high-end seals, with the total investment of 180 million BRL （about USD 80 million）.     

Novel Bifunctional Resins in Metal Ion Separations: Ion Exchange/Coordination Resins and Ion Exchange/Precipitation Resins

Abstract

Dual mechanism bifunctional polymers (DMBP's) as metal ion extractants are described within the context of two new examples. The carboxylic acid/pseudocrown resin is a new example of the DMBP class of resins described as ion exchange/ coordination resins. The polyethylene glycol ligand within the resin functions as a coordinating site for metal ions which are brought into the resin via ion exchange with the acid ligand. Initial studies with alkali metal ions are presented. The third general class of DMBP's is also presented. In this case, precipitation is the reaction occurring along with ion exchange thus yielding the ion exchange/precipitation resins. Barium recovery from aqueous solution via barium sulfate precipitation is described.     

离子交换树脂复苏技术在化肥厂脱盐系统的应用

大庆石化分公司化肥厂脱盐水装置共有3列浮动床,每列均有阳浮床、阴浮床和混床,所用原水为石灰软化水.2002年经过技术改造将合成工艺冷凝液和尿素水解水投入脱盐系统部分代替石灰软化水,提高了浮床的周期制水量,2003年4月又将尿素蒸汽冷凝液投入脱盐系统,进一步提高了浮床的周期制水量.     

The Effect of Surface Composition and Structure on Elementary Chemical Reactions on Metallic Substrates

Studies of chemical reactions on well-defined surfaces have considerable potential for providing fundamental knowledge of surface reactivity and guidelines for the understanding of catalytic materials. with the use of low energy election deffraction (LEED)[1,2] surface structures can be diferentiated and the effect of these structures on surface reactivity determined. In addition, the relative case of obtaining surfaces of known composition utilizing Auger electron spectroscopy (AES)[3-5] makes it possible to study metal surfaces with less than 1% impurity and, moreover, to prepare surfaces with known coverages of adatoms such as carbon, oxygen, and sulfur in order to study the effects of these spacies on the activity and selectivity of the surface for given reactants. In some cases, as illustrated of the surface adatoms.     

Ion Exchange Resin Applied to Obtain Clarified Cashew Juice

The condensed tannins present in cashew apple juice provide high astringency, which is undesirable for this product. This study aimed to remove the cashew apple juice tannins by ion exchange for obtaining the clarified cashew apple juice (cajuína). Two strong base resins were used (macroporous and gel type). The effect of the process variables: temperature, resin:juice ratio, and stirring speed were determined. The macroporous resin presented better results with condensed tannins removal up to 80% in optimal conditions (30°C, ratio 1:6, 122 rpm). The cajuína obtained was clear and translucent, with low astringency, acidity, and °Brix according to Brazilian legislation.     

Strengthening of Alumina by Reactions with Silicon Film on the Surface and Effects of Ion Irradiation

Deposition of Si film on sintered alumina, followed by annealing at 1673 K in air, increased the flexural strength by ∼28%. Mullite formation on the surface was confirmed by X–ray diffraction analysis. Ion irradiation of the Si/alumina interface, followed by annealing, produced anorthite but not mullite, and the flexural strength also increased by ∼35%. Thermal expansion mismatch between surface compounds and the alumina body may be responsible for the strengthening.     

Hijacking Chemical Reactions of P450 Enzymes for Altered Chemical Reactions and Asymmetric Synthesis

Cytochrome P450s are heme-containing enzymes capable of the oxidative transformation of a wide range of organic substrates. A protein scaffold that coordinates the heme iron, and the catalytic pocket residues, together, determine the reaction selectivity and regio- and stereo-selectivity of the P450 enzymes. Different substrates also affect the properties of P450s by binding to its catalytic pocket. Modulating the redox potential of the heme by substituting iron-coordinating residues changes the chemical reaction, the type of cofactor requirement, and the stereoselectivity of P450s. Around hundreds of P450s are experimentally characterized, therefore, a mechanistic understanding of the factors affecting their catalysis is increasingly vital in the age of synthetic biology and biotechnology. Engineering P450s can enable them to catalyze a variety of chemical reactions viz. oxygenation, peroxygenation, cyclopropanation, epoxidation, nitration, etc., to synthesize high-value chiral organic molecules with exceptionally high stereo- and regioselectivity and catalytic efficiency. This review will focus on recent studies of the mechanistic understandings of the modulation of heme redox potential in the engineered P450 variants, and the effect of small decoy molecules, dual function small molecules, and substrate mimetics on the type of chemical reaction and the catalytic cycle of the P450 enzymes.     

Enrichment Factor,Height of Separation Unit,and Separation Efficiency by Ion Exchange with Chemical Reaction

Abstract

The enrichment factor (?_u) in the separation unit of ion-exchange and chemical reactions is a function of the enrichment factor of the chemical reaction (?_r,s) and the “equilibrium coefficients” (ζ) which are determined only by the distribution of the ions in both the solution and ion-exchange phases. The factor can be simply expressed as ?_u = ζ?_r,s. The height of the separation unit is the sum of heights due to ion exchange, chemical reaction, and flow pattern. The height is also due to the “kinetics coefficient” (ζ), which is a function of the distribution as well as the “equilibrium coefficient.” The separation efficiency is proportional to ζ/√υ, both of which depend on the concentration of ions in the unit. Several schemes for the separation units are also discussed.