环境工程中的化学反应技术及其应用

在环境工程中,水处理是其中至关重要的一项内容,水资源短缺已经成为制约我国经济与社会发展的一项主要因素,为此开展污水深度处理,合理分配水资源等工作已经成了我国当前的一项重要任务,但当前很多的水源处理措施,都忽略了处理过程中对于水资源的节约,而化学反应技术中超滤膜技术则可以有效解决这一问题,为水源处理工作提供帮助。因此在文中我们在文中以超滤膜技术在环境工程污水处理中的应用进行了简单的分析与探讨。

超临界化学反应技术及其应用

采用环境友好的溶剂在超临界状态下进行的化学反应,能加快化学反应速率,提高反应的产率和选择性,方便地实现反应分离过程的一体化。笔者就其在聚合反应、羰基化反应、长链烷烃脱氢、废水处理、聚合物解聚、酶催化等方面的应用作了简要的阐述。

我国通用智能化学反应控制技术获重大突破

由中国科学院理化研究所开发研制的通用智能化学反应控制技术获得重大突破,并已具备整机制造条件。目前已有60台整机应用于科研、实验领域,4台整机应用于工业化生产领域,各项运行指标均达到设计要求,流量控制精度可达0.5％,经有关专家认定达到国际先进水平。 该装置是在感光乳剂制备实验装置基础上研制出来的。它集化工工艺、化工机械、自动控制、通讯。

我国通用智能化学反应控制技术获重大突破

由中国科学院理化研究所开发研制的通用智能化学反应控制技术获得重大突破，并巳具备整机制造条件。目前已有60台整机应用于科研、实验领域，4台整机应用于工业化生产领域，各项运行指标均达到设计要求，流量控制精度可达众0．5％，经有关专家认定达到国际先进水平。

碳化硅衬底磨抛加工技术的研究进展与发展趋势

碳化硅衬底难加工的材料特性叠加其大尺寸化、超薄化的放大效应,给现有的加工技术带来了巨大的挑战,高效率、高质量的碳化硅衬底加工技术成了当下的研究热点.本文综述了碳化硅衬底机械磨抛加工技术和化学反应磨抛加工技术的研究进展,对比各类磨抛技术的特点,指出碳化硅衬底磨抛加工技术面临的挑战和发展趋势,以期为大尺寸碳化硅衬底的高质量、高效率、低成本加工提供新的思路和方法.

令人瞩目的生物反应技术

生物反应技术是当今世界上新兴的高技术领域的重要组成部分,近年来在这方面的研究与进展愈来愈为世人所瞩目。特别在化学工业上的逐步推广和应用,给传统的化学工业注入了新的活力。目前,西方各国及日本的许多大型企业,如英国的 ICI、美国的杜邦、道化学、德国的拜耳及日本油脂公司等重视利用生物反应技术改造传统的化学反应过程,从而制得的丙烯酰氨、癸二酸。

Gas-Liquid Microreaction Technology： Recent Developments and Future Challenges

Gas-liquid microreaction technology has shown great potential in a variety of industrial relevant mass transfer operations and reactions. This paper outlines the current research status of this technology with emphasis on reactor design, hydrodynamics and mass transfer phenomena as well as reaction applications. The future challenges of this important technology are also summarized.

C-type natriuretic-peptide-potentiated relaxation response of gastric smooth muscle in streptozotocin-induced diabetic rats

AIM: To study the sensitivity of gastric smooth muscle to C-type natriuretic peptide (CNP) in streptozotocin (STZ)-induced diabetic rats. METHODS: The spontaneous contraction of a gastric smooth muscle strip was recorded by using physiological methods in rats. The expressions of CNP and natriuretic peptide receptor-B (NPR-B) in gastric tissue were examined by using immunohistochemistry techniques in the diabetic rat. RESULTS: At 4 wk after injection of STZ and vehicle, the frequency of spontaneous contraction of gastric smooth muscle was significantly reduced in diabetic rats, and the frequency was decreased from 3.10 ± 0.14 cycle/min in controls to 2.23 ± 0.13 cycle/min (n = 8, P < 0.01). However, the amplitude of spontaneous contraction was not significant different from the normal rat. CNP significantly inhibited spontaneous contraction of gastric smooth muscle in normal and diabetic rats, but the inhibitory effect was significantly potentiated in the diabetic rats. The amplitudes of spontaneous contraction were suppressed by 75.15% ± 0.71% and 58.92% ± 1.32% while the frequencies were decreased by 53.33% ± 2.03% and 26.95% ± 2.82% in diabetic and normal rats, respectively (n = 8, P < 0.01). The expression of CNP in gastric tissue was not changed in diabetic rats, however the expression of NPR-B was significantly increased in diabetic rats, and the staining indexes of NPR-B were 30.67 ± 1.59 and 17.63 ± 1.49 in diabetic and normal rat, respectively (n = 8, P < 0.01).CONCLUSION: The results suggest that CNP induced an inhibitory effect on spontaneous contraction of gastric smooth muscle, potentiated in diabetic rat via up-regulation of the natriuretic peptides-NPR-B-particulate guanylyl cyclase-cyclic GMP signal pathway.

A new two-dimensional experimental apparatus for electrochemical remediation processes

Electrochemical extraction of contaminants from soils is a promising soil decontamination technology. Various experiments have been conducted to study electrochemical reactions and geochemical processes in the electrochemical extraction using different experimental apparatuses. This paper presents the development of a new closed two-dimensional(2D) apparatus that can better simulate the field application of the technology and accurately monitor the most important electrochemical parameters to understand the process. The innovative features of the new apparatus include the outer and inner electrodes designed to apply a non-uniform electrical field across the specimen as in the field electrochemical remediation process, the probes installed to measure the 2D distribution of electrical voltage, and the gas and fluid volume measurement devices used to accurately monitor the gas generation and electroosmotic flow rates at both electrodes as a function of time. The components of this new apparatus and the features of each component are described. The operating procedure and some typical results from three experiments with the apparatus are demonstrated. The results show that the variation of the gas generation rate is in good agreement with the electric current. Their relation provides a valid evaluation for electrochemical behavior of the system and Faraday's laws of electrolysis. The 2D profiles of cadmium concentration and voltage distribution at the end of the experiment reveal the great effects of a non-uniform electrical field on the contaminant mobilization.

Experimental Study on Local Mass Transfer of Structured Packing with the Method of Flow Visualization

A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method （AAM） that yields the surface distribution of transferred mass by analyzing the color distribution on a filter paper with the results of the color chemical reaction. A digital image processing technology is applied for data visualiza-tion. The three-dimensional plot of the local mass transfer coefficients shows that there exist three peak values on different positions of a unit cell of structured packing. In order to improve mass transfer efficiency of the structured packing, one piece of baffle is added between packing sheets. As a result, the average mass transfer coefficient increases by （10 20）% and the pressure drop decreases by （15-55）%.

Thermal Analysis of Composite Cements

The hydration of cement compounds gives hydrated compounds, which allow linking together, the different particles and aggregate of cement, and gives the concrete the required qualities. The dynamics of hydration reactions will depend on many factors, such as the fineness of cement, the ratio w/c during hydration, temperature, mixing technique, and the presence of additives in blended cement, as pozzolan, tuff and slag from blast furnaces. We studied the thermal and kinetic reactions of Portland cement hydration, and its variants with different additions using a differential scanning calorimetric analysis. The parameters from these models of curves allow us to evaluate the enthalpies, and the degree of progression of this blended cement, and finally determine their activation energies. We can say that the hydration of Portland cement is due to a series of reactions as （ C3S,C2S,C3A and C4AF reactions with water） and each of them, has its own kinetic, the experimental measurement of the heat of hydration, allows us to represent the overall kinetics of these reactions values of activation energy, they are therefore apparent and global energy. In our experiments, significant differences in these physicochemical parameters were observed, depending on the additive used.

角膜胶原交联技术的应用与进展

角膜胶原交联技术是用于治疗角膜扩张性疾病的一项新方法。核黄素／紫外线角膜胶原交联技术可延缓或阻止角膜扩张疾病的进展，并其改善视力、散光和角膜地形图参数。但该技术仍存在应用局限，现已有各种改进的技术方案。激光光化学交联技术作为一项新的安全有效的交联技术正逐渐成为研究热点。本文综述以上两种胶原交联技术的原理、交联效能，临床应用及并发症和应用局限。

Electrochemical behavior and electrowinning of palladium in nitric acid media

In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of electrochemical reactions associated with palladium were recognized,indicating that Pd(II)undergoes a single step two-electrons irreversible process.Electroreduction reaction of Pd(II)and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid,respectively.Stirring could facilitate the reduction of Pd(II)in relatively low nitric acid concentration(3 mol/L).The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K.The diffusion coefficient of Pd(II)increased from 1.89×10 8cm2/s at 288 K to 4.23×10 8cm2/s at 318 K,and the activation energy was calculated to be 21.5 kJ/mol.In electrowinning experiments,SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases,which is uniform all over the entire surface of Pt electrode.The recovery ratios of Pd at different nitric acid concentrations are high,and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration.When stirring was introduced during electrolysis,the electrodeposition rate of Pd increased substantially.

A comparative electrochemical investigation of silicon nanowires formation via metal-catalyzed electroless etching

In this study, the electrochemical behavior of monocrystalline bare Si and Ag-coated Si in hydrofluoric acid （HF） solutions with and without hydrogen peroxide （H202） was systematically tested with an electrochemical technique. By analyzing the po- larization curves, the corrosion processes were quantified and the etchants which govern the formation of silicon nanowires （SiNWs） were determined. It was discovered that both H202 and Ag enhanced the reduction reactions, irrespective of the con- ductivity type and doping concentration of Si. It is believed that the formation of SiNWs via Metal-Catalyzed Electroless Etching is a process controlled by cathodic reduction reactions.

Cryo-EM for nanomaterials:Progress and perspective

Cryogenic electron microscopy(cryo-EM)has extensively boosted structural biology research since the“resolution revolution”in the year of 2013 which was soon awarded the Nobel Prize in Chemistry in 2017.The advances in camera techniques and software algorithms enabled cryoEM to routinely characterize the three-dimensional structures of biomolecules at near-atomic resolution.Biomolecules are basically sensitive to electron irradiation damage,which can be minimized at cryo-temperature.This principle has inspired material scientists to characterize electron beam-or air-sensitive materials by cryo-EM,such as the electrodes in the lithium-ion battery,metal-organic frameworks(MOFs),covalent-organic frameworks(COFs)and zeolites.In addition,the reaction systems can be fast-frozen at vitreous ice in cryoEM,which correspondingly preserves the materials at the close-to-native state.Herein,we summarized the development and applications of both the cryo-EM technique and other emerging cryo-techniques in materials science,and energy storage and conversion.Cryo-EM techniques,capable of the direct observation of sensitive materials and electrochemical reaction processes,will greatly renew our understanding of materials science and related mechanisms.