Comparison of diester waste treatment by conventional andbipolar electrodialysis

Diester manufacturing plants produce large quantities of glycerol solutions. Their economic development requiressodium sulfate elimination to obtain glycerol rates over 80% of the initial content. Conventional electrodialysis (ED) and bipolar electrodialysis (BED) were investigated for their performances in the demineralisation of effluents. Results indicate that both ED and BED achieve the demineralisation objective with a global loss below 2.5% of the initial glycerol. Salt fluxes are twice as high with a bipolar membrane, bipolar membranes having however a lower efficiency. Hence energetic consumption is higher for BED. This technique also leads to the production of alkali and acid solutions which are useful to the diester process. The glycerol content of the solutions acts, via its viscosity, on the energetic cost of fluid pumping and on energetic efficiency. Therefore, ED or BED has to be used before the preconcentration of the solution.     

COUPLING OF UREA HYDROLYSIS AND AMMONIUM REMOVAL IN AN ELECTRODIALYZER WITH IMMOBILIZED UREASE

A five-compartment electrodialyzer with immobilized urease was developed for the removal of urea from aqueous solution. The immobilized urease supported on polyurethane foam was placed in the central (dilute) compartment, where urea was hydrolyzed and the products were transported simultaneously into the concentrate compartments on its both sides by electrodialysis. The effect of the kinds of buffer salts on the product distribution of urea hydrolysis between two concentrate compartments was investigated under phosphate and citrate buffer systems. It was found that no ammonium-nitrogen was present in the concentrate compartment on the anodic side for both buffer systems. This result could be due to the half-life of carbamate ions was too short to transport into anodic concentrate compartment before they decomposed to ammonium carbonate. The removal of urea from buffer-free aqueous solution was also studied. It was shown that urea and its hydrolysis product could be removed by the electrodialyzer with immobilized urease.     

Electrodialysis with brine solutions oversaturated with calcium sulfate

Electrodialysis (ED) was applied to concentrate brine solutions of various concentrations — similar to effluentsfrom the desalination of brackish and industrial water — to about 20%. The consequent reduction in effluent volumes would facilitate a reduction in disposal costs. The energy requirement for concentrating solutions from 70 to 300 mN (0.4-1.8%) to 3.9 N (20%) was in the range 1.5-7.1 kWh/m³, in contrast to approximately 25 kWh/m³ by thermal evaporation. With the aim of preventing precipitation of CaSO4 on the membranes, laboratory-scale ED experiments were carried out on solutions of different compositions to determine the conditions that would lead to the precipitation of excess gypsum on gypsum seeds in a separate precipitator. The results were then applied in a pilot-scale ED unit in which the brine that circulated through the ED brine cells passed through a separate CaSO, precipitator containing gypsum seeds.     

The possibility of the desalination of actual 1,3-propanediol fermentation broth by electrodialysis

Electrodialysis (ED) was employed to remove the organic and inorganic salts from actual 1,3-propanediol (PDO) fermentation broth. These salts cause many problems during the purification of PDO if not removed. Suitable operation parameters such as applied potential and the flow rate of streams were selected to ensure a stable and durative desalination process for PDO fermentation broth. Under these conditions, the membrane fouling can be alleviated effectively by changing pole and cleaning membranes so that further industrial production is possible. The experiment results show that about 90% of organic acid salts in PDO broth are removed by the ED process. In addition, a simulated diffusion PDO experiment proved that the diffusion of PDO results in its loss from fermentation broth and the loss ratio is less than 6% under the chosen operating conditions.     

关于快速生长KDP晶体生长装置的改进

本文是建立在KDP晶体快速生长方法基础之上.为了更适合于晶体生长,对电极、离子换膜、籽晶、红外线加热方式、以及水封装置等方面,进行了改装,从而使KDP晶体快速生长装置更进一步完善.     

Synthesis and characterization of new proton exchange membrane deriving from sulfonated polyether sulfone using ionic crosslinking for electrodialysis applications

In this research work, the synthesis and characterization of new ion exchange membranes made from sulfonated polyether sulfone (S PES) crosslinked by aminated PES (NH2 PES) crosslinking reagent have been investigated for electrodialysis (ED) applications. Sulfonated and aminated PES have similar chemical structures that allow a good compatibility, the only difference between them is their functional groups. This membrane (called HNH2) has been obtained by reaction between S PES with 1.3 SO₃H groups per monomer unit and the calculated equivalent amount of NH2 PES. Three HNH2 membranes have been fabricated with different degrees of sulfonation. The HNH2 membranes properties have been evaluated using different characterization analysis. The results have shown that HNH2 membranes appear to be very promising candidates for electrochemical applications.     

Soy sauce desalting by electrodialysis

In this work, microfiltered samples of a traditional soy sauce containing 15.1 ± 0.3% (w/v) of sodium chloride were desalted using a laboratory-scale electrodialyser equipped with a stack composed of nine cation- and eight anion-exchange membranes so as to minimise the health risks associated with the consumption of high-salt foods, as well as to allow its full freezing at the current industrial freezing temperatures and accurate dosage in the formulation of multi-component ready-to-serve frozen meals.     

Electrochemical Analysis of Ion-Exchange Membranes with Respect to a Possible Use in Electrodialytic Decontamination of Soil Polluted with Heavy Metals †

Abstract

Transport numbers in different metal chloride solutions were estimated using the emf method for two ion-exchange membranes: Ionics CR67 HMR412 (cation-exchange membrane) and Ionics AR204 SXRA 7639 (anion-exchange membrane). The cation-exchange membrane was found to work nearly ideally for NaCl and CaCl₂ solutions even at high concentrations, whereas deviation from ideality was seen for ZnCl₂ and CuCl₂ solutions. The anion-exchange membrane showed transport numbers for the anion around 0.95 for NaCl, CaCl₂ and ZnCl₂ solutions for the concentration range investigated. Electrodialytic desalting experiments taken as a simplified simulation of the electrokinetic decontamination method showed that it was possible to remove all ions in the simulated soil volume, with a sharp increase in the potential difference over the soil volume as a result, and that it was possible to control the metal content in the different solutions in the electrodialytic decontamination method.

     

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.     

双极膜及其研究进展

介绍了双极膜水解离电渗析技术的原理,双极膜的制造、应用以及国内外对双极膜的研究及发展动向。