Showing papers on "Electrodeionization published in 2002"

Fractional deionization process

Abstract: A liquid treatment process is described for sequential removal of ionic species of progressively decreasing ionic strength without precipitation or 'scaling.' An embodiment of the invention includes dual electrodeionization operations. The first electrodeionization operation is performed at a voltage calculated to remove strongly ionized species such as calcium and magnesium from the feed water without scaling. The product of the first electrodeionization operation is then subjected to a second electrodeionization operation. The second electrodeionization operation is performed at a voltage greater than the first electrodeionization operation, and is designed to remove more weakly ionized species such as silica and atmospheric carbon dioxide. The danger of precipitation or 'scaling' normally present during electrodeionization of weakly ionized species is not present in this invention, because the strongly ionized species responsible for scaling at higher voltages have already been removed from the feed stream through the first electrodeionization operation. More than two successive electrodeionization operations may be performed if desired. Multiple electrodeionization operations may occur in a single electrodeionization stack or in multiple electrodeionization stacks.

Control of water treatment system with low level boron detection

Abstract: A water treatment system and method including a membrane-based boron removal unit includes a boron analyzer for detecting the concentration of boron in a treatment stream. The boron removal unit can be a reverse osmosis (RO) or electrodeionization (EDI) treatment unit. A controller responds to the detected boron concentration to control an operation of the RO or EDI units. In an EDI system, the controller may adjust current or voltage supplied to match current to changes in ionic load and maintain a portion of the dilute cell in a substantially regenerated state. In an RO system, the controller may control the high pressure side flow rate, the brine blowdown rate, the product water permeation rate, pH, or feed rate of chemicals in response to the detected boron concentration value.

Preparation and characterization of cation-exchange media based on flexible polyurethane foams

Abstract: Continuous electrodeionization (CEDI) is used to deionize a solution to a level attained by mixed bed ion exchange without chemical regeneration. However, handling of ion-exchange beads is laborious for a large-scale CEDI system. In this study, a new type of ion-exchange polyurethane foam containing sulfonic acid groups was synthesized by bulk condensation polymerization for use as a cation-exchange medium. Polyurethanes are synthesized by the reaction between a diisocyanate and a polyol. Toluene diisocyanate 2,4-80%, 2,6-20% (http://www.tciamerica.com/) was reacted with poly(propylene glycol) to synthesize a polyurethane prepolymer and then N,N-bis(2-hydroxylethyl)-2-aminoethanesulfonic acid (BES) was added to give a foam containing sulfonic acid groups. The functional polyurethane prepolymers were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), and gel permeation chromatography (GPC). The ion-exchange capacity was measured as 2.5 meq/g, and the equiconductance point of the polyurethane foams were 14, 19, 29, and 33 μ/cm for BES molar ratios of 0.5, 0.7, 1.0, and 1.5, respectively. The porous plug model shows that the current flows dominantly through the solution phase of the polyurethane foam, which indicates the polyurethane foam is a suitable medium for use in a CEDI operation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1773–1781, 2002

Study on the influence of applied voltage and feed concentration on the performance of electrodeionization

Abstract: Wastewaters from electroplating industries are usually contaminated with nickel up to 1000 mg/L. According to environmental regulations worldwide, nickel concentration on wastewaters must be controlled to an acceptable level before being discharged to the environment. This paper offers an alternative way to develop an efficient effluent-free technology to reduce the nickel content of rinse water so that the treated water could be recycled for rinsing and subsequently to workout methodology to recover nickel by electrodeionization (EDI). Electrical voltage and initial nickel concentration were varied to study the effect of the parameters. Results showed that EDI could remove nickel effectively which gives an outstanding result in terms of product quality. Nickel concentration on diluate chamber decreased up to 99% after 60 and 180 minutes for nickel concentration of 300 and 1000 mg/L, respectively. Meanwhile, the increase of electrical voltage led to faster nickel removal.

Apparatus for water treatment having electrodeionization device

Abstract: An apparatus 40 for water treatment has an electrodeionization device 34 to which power is supplied from a cell stack 30 of a fuel cell. The direct current power is transformed in its voltage by a transformer 35 and then supplied to the electrodeionization device without passing through an inverter. Efficiency of power supply is improved, and the apparatus is reduced in its equipments costs and a scale thereof. The apparatus 40 treats water from and relating to the fuel cell such as water produced by reaction of oxygen and hydrogen on the cathode, cooling water of the cell stack, water for steam fed to the reformer, and so on.

Electrodeionization in pharmaceutical water treatment

Abstract: Electrodeionization is a technology that uses ion-exchange resin sheets and beads as well as electrical potential to remove undesirable contaminants from preheated feed water. A significant advantage to using this technology in place of conventional mixed-bed ion-exchange technology is the elimination of the need for on-site regeneration chemicals.

Electro-deionization device and method for operating the same

Abstract: PURPOSE: An electrodeionization apparatus is provided which restrains the diffusion of silica from the concentrating compartments, thus capable of producing product water with an extremely low silica concentration. CONSTITUTION: Feed water, fed through an inlet(6) into a desalting compartment(8), flows around the end(4a) of an anion-exchange membrane(4) surrounding an anode(2a). The feed water enters into a portion defined between the anion-exchange membrane(4) and a cation-exchange membrane(5), and flows around the end(5a) of the cation-exchange membrane(5) surrounding a cathode(3a). Then, the water to be treated further flows around the ends(4b,5b) of ion-exchange membranes(4,5) surrounding an anode(2b) and a cathode(3b), respectively, and then flows out through a product water outlet(7). A part of product water is supplied to the concentrated water circulating within the concentrating compartment(30,40). A part of the concentrated water flowing out of the concentrating compartment(30,40) is added to concentrated water circulating within the concentrating compartment(10,20). The diffusion of silica from the concentrating compartment is restricted. As a result, final product water containing extremely low silica concentration is obtained.

1 Removal of metal ions and recovery of boron using electrodeionization process in the primary cooling water of nuclear power plant

Abstract: PURPOSE: A recovery of boron and removal of metal ions from primary cooling water of nuclear power plant by using electrodeionization(EDI) process is provided, which can reduce treatment cost of waste drastically by changing packing method of ion exchange resin from the existing electrical deionization equipment, and can protect workers from dangers of exposure to radioactivity. CONSTITUTION: The system comprises a pretreatment device(100) and three electrical deionizing stacks(210) set serially. The electrical deionizing stacks(210) are composed of a cation exchange membrane and an anion exchange membrane, at the both sides of which concentration chambers are equipped and between the exchange chambers a desalting chamber is provided. In the desalting chambers, a cation exchange matter, an anion exchange matter and mixed ion exchange matter of cation and anion are filled serially from the water inlet.

An electrodeionization apparatus comprising subdesalination chambers, and an electrodeionization method

Abstract: Two sub-desalination chambers d1 and d2 are defined by a cation exchange membrane 3 on one side, an anion exchange membrane 4 on the other side, and an intermediate ion exchange membrane 5 in between and are filled with ion exchange materials 8 to construct a desalination chamber D. Concentrating chambers 1 are provided via the cation exchange membrane 3 and the anion exchange membrane 4 on both sides of the desalination chamber D. The desalination chamber D and the concentrating chambers 1 are provided between an anode 7 and the cathode 6. While a voltage is applied between the anode 7 and the cathode 6, water is supplied to one of the two sub-desalination chambers d2 and then, water discharged from the first sub-desalination chamber d2 is supplied to a second sub-desalination chamber d1. Concentrate water is supplied to the concentrate chambers. With this configuration, the impurity ions in the water to be treated flowing in the desalination chambers D are concentrated in the concentrate water and deionized water is produced.

Electrodeionization water purification device

Abstract: A porous ion exchanger which has a continuous pore structure comprising interconnected macropores and, formed in the walls of the macropores, mesopores having an average diameter of 1 to 1000 νm, has a total pore volume of 1 to 50 ml/g, has ion exchange groups being uniformly distributed, and has an ion exchange capacity of 0.5 mg equivalents/g-dry porous exchanger or more. The porous ion exchanger is capable of being used as the ion exchanger to be packed in a deionizing module of an electric type deionized water production apparatus, a solid acid catalyst, an adsorbent and a packing material for a chromatograph.