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= Water Deionization =

Introduction
Deionization is the process that embraces the removal of all charged constituents or ionizable salts (both inorganic and organic) from solution, therefore the solution become at the end totally charge free (has zero net charge). Deionization also known as deashing or demineralization, because of the removal of minerals which are known to be one of main sources of ions when present in water in the form of salts. Deionization process is based on cation (+) and anion (-) resins, the ions are removed through passing the water across several stages of electrically charged resins, these resins attract the salts and the ions contained in the water resulting in highly filtrated water. Deionized water has several uses, for instance, it is used widely in the manufacturing field like water cycle at petrochemical plants, it is also used in lead acid batteries and it is commonly used in the pharmaceutical field as an additive for medicine and its preparations.

Mechanism of Deionization
The most common Deionization (DI) process is done by deionization filters, these filters have many names: Ion Exchange, Strong Acid/Strong Base, Polishing, Nuclear Grade. Nuclear grade DI filters can remove Inorganic chemicals down to very low parts per billon (PPB) levels. This makes them excellent for producing Ultra-Purified water. Water of this quality is used with the most sensitive laboratory analytical instruments, which are designed to detect chemicals at extremely low concentration levels.

Deionization filters function by exchanging positive hydrogen and negative hydroxyl molecules for the positive and negative contaminant molecules in the water. Positive chemicals, like calcium, exchange places with the hydrogen molecules and negative chemicals, like iodine, exchange places with the hydroxyl molecules. Over time, positive and negative contaminants in the water displace all the active hydrogen and hydroxyl molecules on the DI resin and the filter must be replaced. Regeneration of the deionization filter is possible, but only in an industrial environment setting.

Two-bed Deionizer
The two-bed deionizer consists of two vessels – one containing a cation-exchange resin in the hydrogen (H+) form, and the other containing an anion resin in the hydroxyl (OH-) form. Water flows through the cation column, whereupon all the cations are exchanged for hydrogen ion. To keep the water electrically balanced, for every monovalent cation such as: Calcium & Magnesium.

Same principal applies when considering anion-exchange. The water with removed cations then flows through the anion column. This time, all the negatively charged ions are exchanged for hydroxide ions which then combine with the hydrogen ions to form water (H2O).

Mixed-bed Deionizer
In mixed-bed deionizers the cation-exchange and anion-exchange and anion-exchange resins are intimately mixed and contained in a single pressure vessel. The thorough mixture of cation-exchangers and anion-exchangers in a single column makes a mixed-bed deionizer equivalent to a lengthy series of two-bed deionizer is appreciably higher than that produced by a two-bed plant.

In the Industry
is used mostly for laboratory, Its favorability is thanks to its high purity content and is suitable when normal water and distilled water might negatively affect mechanical or biological functions due to them having a lower purity level. As this is a topic of much interest, here are some of the benefits of using deionized water With low conductivity, deionized water is also a good cooling agent for heavy equipment such as High power lasers, Engine cooling systems, and Medical equipment.

Pharmaceutical Field
Water for injection (WFI) which is the product of highly purified water or Deionization process. WFI  in pharmaceutical applications Water For Injection  is sterile, non-pyrogenic, distilled water for the preparation of products for parenteral use. It contains no added substance and meets all the requirements of the tests for purified water. It must meet the requirements of the pyrogen test. The finished water must meet all of the chemical requirements for Purified Water as well as an additional bacterial endotoxin specification. Since endotoxins are produced by the kinds of microorganisms that are prone to inhabit water, the equipment and procedures used by the system to purify, store, and distribute Water for Injection must be designed to minimize or prevent microbial contamination as well as remove incoming endotoxins from the starting water. Water for Injection systems must be validated to reliably and consistently produce and distribute this quality of water. There are many Purposes for WFI. Like for the production of parenteral products/formulation and for cleaning of parenteral product-contact components.

Acid Batteries
In lead acid batteries, water purity can have a major effect on product performance. Water usage needs to be viewed as a priority for maximum performance. Therefore the Deionized water is an ideal choice for this kind of batteries, since it is consider the most purified water which has a low impurities. On the other hand it is expensive compared with the distilled water which has a lower level of impurity. The following table represents the maximum allowable amount of impurities in water for battery.

Table 1: recommended maximum allowable impurities in water for battery use.

Textiles
Water washing is one of the most useful cleaning treatments for paper and textile conservators. Where an artifact can be safely wet-cleaned, water washing can often improve the appearance more than any non-aqueous cleaning method. The process can also improve the long-term stability of an artifact by removing water-soluble pollutants and harmful degradation products. As water washing is widely used, it is important for paper and textile conservators to understand its impact on artifacts. One of the greatest concerns is the choice of water quality. At the root of this is the fact that deionized (DI) water is the choice. Research has shown that washing with deionized water can remove calcium and magnesium ions from cellulose.



Microelectronics/Semiconductor Manufacturing
In semiconductor manufacturing, deionized water's properties for absorbing minerals, enhancing detergents and residue-free drying make it useful for rinsing and cleaning semiconductor wafers. It is also used in wet etching, bacterial testing and many other processes throughout the fabrication facility.

Cosmetics
Deionized water is often used as an ingredient to add purity, stability and performance in many hair care, skin care, body care, baby care, sun care and makeup products, where it is sometimes referred to as "aqua" on product ingredient labels.

Energy Research
Because of its high relative dielectric constant, deionized water is used as a high voltage dielectric in many pulsed power applications for energy research, such as the Sandia National Laboratories Z Pulsed Power Facility.

Car Wash
When used as a rinse after washing cars, windows, and similar applications, deionized spot-free rinse water dries without leaving spots caused by dissolved solutes, eliminating post-wash wipe downs.

Food and Beverage Processing
Deionized water is used as both an ingredient and a process element in food and beverage processing. As an ingredient, it offers stability, purity and sanitation. As a process element, it is used for effective sanitation.

Boiler Water Treatment Equipment
Deionized water is used to pretreat boiler feed water to reduce scaling and energy use and to control deposition, carryover and corrosion in the boiler system. As such, DI water is an essential element in boiler water recycling.

Cooling Towers
Deionized water can pretreat cooling tower make-up water to reduce scaling and energy use in power plants, petroleum refineries, petrochemical plants, natural gas processing plants, food processing plants, semiconductor plants, and other industrial facilities.