发酵液中乳酸的电渗析法分离

采用电渗法分离发酵液中低浓度乳酸,考察了电渗析器的操作条件对极限电流密度和乳酸电年速率的影响,并分别用修正的Ｗｉｌｓｏｎ公式和乳酸电渗析速率方程描述了它们之间的关系。     

Effect of Process Parameters on Separation Performance of Nitrate by Electrodialysis

Abstract

The electrodialytic separation of nitrate from water was investigated as a function of feed characteristics such as applied voltage, feed flow rate, and nitrate concentration in the solution. The separation performance was evaluated in terms of percent removal of nitrate, process time, and energy consumptions. TS‐1‐10 electrodialysis equipment (Tokuyama) was used in experimental studies. During the unsteady state run of the ED system, both inlet and outlet concentrations of nitrate and conductivities of streams were measured at certain time intervals until the current drops to 0.01 A. It was obtained that the percent removal of nitrate from the solution increased when the concentration of nitrate in the feed solution increased. The operation time became shorter when a high potential was applied.     

Separation of Nickel and Cobalt by Electrodialysis Using Ion-Exchange Membranes in the Presence of EDTA

Abstract

Electrodialytic separation of Ni²⁺ and Co²⁺ cations has been realized by using ion-exchange membranes in the presence of EDTA by preferentially complexing Ni²⁺(Ni²⁺ concentration = EDTA concentration). The degree of complexation is calculated as a function of the pH and of the concentration by using data taken from the literature. Due to a systematic study of the influence of the different separation parameters (nature of the membranes, flow rate, electric current intensity, pH), the conditions_of_separation have been optimized on a computer, and then pure solutions of nickel and cobalt ions have been obtained experimentally. The decomplexation of Ni²⁺ is accomplished in acidic medium by cooling.     

Effect of Operating Parameters on the Condensation of Ammonium Sulfate by Electrodialysis

The separation of ammonium sulfate from dilute solution by electrodialysis was investigated. From the results obtained, it is suggested that it is feasible to separate ammonium sulfate from aqueous solution by electrodialysis. The removal performance of ammonium sulfate obtained was very satisfactory. The optimal cation and anion membranes were found. The removal efficiencies were influenced by voltage, initial concentration, flow rate and temperature. High voltage and high temperature are beneficial to this separation process, but high fluid flow rate and concentrated initial concentration prolong the operation time required to achieve the target value. It was found that the optimal outlet concentration is 1 g/L, since the operation time is prolonged almost two‐fold if the outlet concentration is decreased from 1 g/L to 0.5 g/L.     

Transfer of Monovalent and Divalent Cations in Salt Solutions by Electrodialysis

Abstract

The selectivity mechanism of transport of Na⁺, Ca²⁺ and Mg²⁺ through commercial monovalent‐cation permselective membranes is investigated in batch electrodialysis experiments with synthetic salt solutions containing monovalent and divalent cations. The role of hydration energy, steric effect, kinetic effect as well as effects of permselectivity of cation exchange membrane has been elucidated with electrodialysis of single solutions (NaCl, CaCl₂, MgCl₂). The mechanism of interferences is investigated in (Na⁺/Ca²⁺, Na⁺/Mg²⁺, Ca²⁺/Mg²⁺ and Na⁺/Ca²⁺/Mg²⁺) mixtures.     

Removal of Fluoride from Geothermal Water by Electrodialysis (ED)

Abstract

Removal of fluoride from geothermal water by electrodialysis (ED) was studied. ED operation was performed according to two methods. In the first method, before the ED operation, the pH of geothermal waters was adjusted to 7?7.5 by the addition of the HCl solution to prevent the precipitation of divalent salts in the concentrate compartment. In the second method, geothermal water was pretreated to precipitate the calcium ions. It was obtained that fluoride was effectively removed from geothermal water by electrodialysis using both of these pretreatment methods. However, it is preferable to use the first method because of its technically simple procedure and lower cost of chemicals used.     

Interaction between Copper(II) Oxide and Aqueous Ammonia in the Presence of Ethylenediaminetetraacetic Acid

The interaction of copper(II) oxide with aqueous ammonia containing ethylenediaminetetraacetic acid (H₄L) is analyzed in terms of formal heterogeneous kinetics and the fractal dimension of the dissolving space. It is shown experimentally that, in the presence of H₄L, the dissolution rate of CuO grows with increasing ammonia concentration. At a fixed ammonia concentration, the dissolution rate of CuO passes through a maximum at an H₄L concentration of 8 × 10^–3mol/l. Two mechanisms of dissolution are suggested, namely, an adsorption and a redox mechanism. The adsorption mechanism involves four intermediate species and implies that the dissolution rate is a fractional rational function of the EDTA concentration. The redox mechanism takes into account the oxide/electrolyte interfacial potential. The role of the CuOHL^3–ion is elucidated, and the kinetic parameters of dissolution are derived.     

Dissolution Kinetics of Manganese(III,IV) Oxides in Sulfuric Acid in the Presence of Ethylenediaminetetraacetic Acid

Dissolution kinetics of manganese(III, IV) oxides in sulfuric acid in the presence of ethylenediaminetetraacetic acid was studied at various pH values and temperatures. Kinetic, spectrophotometric, and electrochemical studies demonstrated that the dissolution rate of manganese oxides is governed by the potential step at the oxide/electrolyte interface and by the solution pH. A mechanism of the dissolution is suggested.     

电渗析法分离中性有机物、强酸和弱酸的实验研究

采用阳膜和复合膜组成的电渗析装置成功地将乙二醛、硝酸和醋酸各个分离并回收，从而取代萃取法工艺，解决了萃取工艺工序多，运行费用大，废液(硝酸和醋酸)污染环境的问题。     

Mechanism for Soil Reinforcement by Electroosmosis in the Presence of Calcium Chloride

Electroosmosis has been extensively employed as an effective method for the dewatering treatment of soils and thus the reinforcement of weak soils. At the microscopic level, this treatment process is inherently complex due to in situ chemical and electrochemical reactions, migration of ions and particles, and the dependence of zeta potential of various particles on the local pH value in the soil. This complexity has hindered further understanding of mechanisms underlying the electroosmosis technology. Here, we design an external electric field in which alternating pulse wave potentials were partially used to adjust the pH value of the soil and manipulate the dynamics of in situ formed nanoparticles and their interconnectivity. The experimental results reveal that the in situ formation of Ca-rich particles, instead of water drainage, may serve as the main mechanism underlying the observed soil reinforcement when using calcium chloride as the treatment electrolyte. The interconnectivity of such particles may be the key for the shear strength improvement without significant settlement of the soil.     

Electrodialysis in water-ethanol solutions: Application to the acidification of organic salts

Up to now, most electromembrane processes have been performed in aqueous media. Here the feasibility of conversion of sodium salts oforganic acids (propionic, butyric and octanoic) was demonstrated in water-ethanol media up to 50% v/v. The alcohol content was the same in all the electrodialysis compartments, and the conversion ratio remained high for sodium propionate and butyrate at 10 and 30 mA.cm⁻². When the length of the linear hydrocarbon chain was increased to sodium octanoate, the conversion ratio was less than 50%. The main interest of using ethanol-water media is the increase of organic acid solubility.     

胶体金免疫层析法快速检测水样品中的镉离子

目的研制检测水样品中镉离子残留的胶体金免疫层析快速检测试纸条。方法采用免疫竞争法,将抗Cd2+-EDTA单克隆抗体-胶体金复合物包被于胶体金结合垫上,并将人工合成的Cd-iEDTA-BSA检测抗原包被在硝酸纤维素薄膜表面,作为检测线(T线),3～5min后,根据颜色直观显示检测结果。对试纸条进行灵敏度、特异性和稳定性验证,并检测添标水样。结果制备的试纸条对镉离子的最低检测限为100ng/ml;除了与Hg2+-EDTA有交叉反应外,与Fe3+、Pb2+、Cu2+等类似物无交叉反应;试纸条在常温下放置8周稳定性良好;检测添标水样的结果与ICP-AES的检测结果一致。结论胶体金免疫层析法操作便捷,稳定可靠,可作为水样中重金属镉离子残留现场检测和监控的有效手段。     

电渗析回收亚氨基二乙酸的实验

通过电渗析回收亚氨基二乙酸的实验研究,考察了不同类型离子交换膜在等电点状况下电渗析脱盐率与有机物损失率之间的关系,并确定了浓差扩散的有效控制方式。实验结果表明,采用电渗析法能够有效处理亚氨基二乙酸废水,电渗析脱盐率>96%,亚氨基二乙酸损失率<0.6%。     

Electrodialysis Application of the Ultrafiltration Permeate of Milk Before and After Reverse Osmosis

Ultrafiltered (UF) milk permeate was concentrated by reverse osmosis (RO). UF and UF + RO samples were then desalted by electrodialysis (ED) to three levels of desalination: 1, 2.5, and 4 % of ash in the dry matter. Ions were analyzed by a new high‐performance liquid chromatography method, which enables simultaneous estimation of cations and anions. ED of UF permeate has some advantages over that of UF + RO samples, including a shorter ED time and a higher average salt flow rate, but RO treatment of UF permeate before ED enables the processing of larger volumes of UF permeate. Therefore, ED of milk permeate, particularly after RO, improves the handling characteristics and may offer advantages for further processing of secondary dairy products.     

Separation of Fermentation Products by Membrane Techniques. II. Conversion of Lactate to Lactic Acid by Electrodialysis

ABSTRACT

The yield of an electrodialysis unit operating for the conversion of lactate to lactic acid (LA) is depressed by low conductivity of the lactic acid solution. Experiments performed with a laboratory electrodialysis unit (ED) designed to establish the limiting current density i_lim for the whole unit and for each of the membrane/solution elements revealed high voltage drops for membranes in contact with the lactic acid solution. By filling the LA compartment with a cation-exchange resin as the conducting turbulence promoter, it was possible to increase i_lim from 2.7 ± 0.3 to 18.3 ± 2.0 mA/cm². With a resin suspension the rate of lactic acid formation was 6.0 mol^{â2 â1}, the current efficiency amounted to 92%, and the energy consumption was 3.3 kWg^â1. A hypothesis for the 7-fold increase of i_lim by filling the LA compartment with a grained conducting resin is presented.     

EDTA配合滴定法测定食盐中的钙含量

钙是人体所不可或缺的营养素之一,但受地域和环境条件的影响,我国人口中缺钙的情况依然存在。目前市场上供应的加钙盐和其他一些营养盐可以满足人们补充体内钙元素的需要,因此研究营养盐中钙的含量具有非常重要的意义。为建立快速简便的钙含量测定方法,采用EDTA配合滴定法测定加钙盐中钙的含量,测定结果加钙食盐中钙含量均符合国家标准。实验操作简单,结果准确,易于推广。     

Seawater Reverse Osmosis Brines as a New Salt Source for the Chlor-Alkali Industry: Integration of NaCl Concentration by Electrodialysis

Seawater RO brines have been identified as an alternative to common NaCl sources for the chlor-alkali industry. Electrodialysis (ED) has been evaluated as a preliminary step of NaCl concentration for these brines. Experimental results showed that ED was an effective concentration technology, where values up to 252 g_NaCl L^?1 were reached at 0.3-0.4 kA m ^?2 with a power consumption of approx. 0.20-0.30 kWh kg^?1 NaCl. As the membranes used (Neosepta CIMS and ACS) were mainly selective for univalent ions, polyvalent ions were partially removed from the brine, benefiting its reuse. NaCl concentrated solutions are to be used as feed brine in the chlor-alkali industry after a purification step.     

分光光度法测定镀镉液中硫脲

根据硫脲在pH值2～3的乙酸介质中可被亚硝酸钠氧化生成硫氰酸和氮气，利用硫氰酸和三氯化铁反应生成红色硫氰酸铁配合物的性质，通过测定硫氰酸铁配合物的吸光度可确定硫脲的含量。