Ion exchangers water softening

Sales of salt for regenerating ion-exchange water softeners have grown steadily in the United States, particularly in terms of revenues. The U.S. salt industry is mature and sales are not likely to increase rapidly. The dry salt industry in the United States and Canada has undergone consoHdation during the 1990s. The number of producers has continued to decline as the major salt producers have acquired smaller operations. Table 6 shows the total amount, including salt in brine, of salt sold or used in the United States for the period 1990—1994. The amount of salt sold or used in the United States in 1994 by product type is (9) ... 

A sodium ion-exchange water softener is required for all boiler plants operating at an MAWP of over 15 psig. 

A common problem associated with the operation of ion-exchange water softeners is due to chloride leakage contamination into the FW following regeneration. This is an operational problem caused by inadequate rinsing and usually is detected in the boiler by a periodic and sudden rapid rise in the boiler water s electrical conductivity and a call... 

For 24-hour, continuous conditioning operation, twin-tank multifunctional units are available with top-mounted Fleck or Autotrol controllers. These controllers provide water meter-initiated, media backwashing, regeneration, and reclassification functions in precisely the same manner as conventional ion-exchange water softeners. 

Some specific applications of ion exchange water softening milk softening (substitution... 

The most common method to treat hard water is through a process called ion-exchange water softening, in which the hardness ions, magnesium and caicium, are exchanged with either sodium or occasionally potassium ions. 

This discovery was made in the 18S0s. and it was the first ion exchange water-softening process utilized commonly. The ion exchangers used today in home softening units are closely related in structure and exchange properties, but are more stable for longterm use. 

Scale control is complex the particular procedure depends on the composition of the feed water. Fortunately, calcium carbonate scale, by far the most common problem, is easily controlled by acidifying the feed or by using an ion exchange water softener to exchange calcium for sodium. Alternatively, an antisealant chemical such as sodium hexametaphosphate can be added. Antisealants interfere with the precipitation of the insoluble salt and maintain the salt in solution even when the solubility limit is exceeded. Polymeric antisealants may also be used, sometimes in combination with a dispersant to break up any floes that occur. 

An ion exchange water softener adds significant amounts of sodium to the water. Thus, it may not be the best choice for drinking water. This is especially true for people on sodium-restricted diets. 

Ion exchange (water softening) the process in which an ion-exchange resin removes unwanted ions (for example, Ca2+ and Mg2+) and replaces them with Na+ ions, which do not interfere with soap and detergent action. (18.4)... 

A household type of ion-exchange water softener is usually adequate for this application because the volume of water to be softened is usually quite small. This type of softener is available from manufacturers like Calgon or MacClean. The softener can be installed inline on the water supply line to the solution tank. When resins (zeolite or synthetic resin) become saturated with calcium (exhausted), the resin (zeolite or synthetic resin) can be regenerated with brine solution made from common salt. 

Hard water contains metallic ions, such as magnesium or calcium ions, that interact with soap to form insoluble films or scum. Hardness is not hazardous to health but may form scale in boilers and clog water pipes. Excess calcium and magnesium can be removed by ion exchange water softeners. SEE ALSO Green Chemistry Neurotoxins Toxicity Water Water Pollution. 

Fig. 6.8-32 Salt briquettes that are used for the regeneration of ion-exchange water softeners...

Fig. 6.8-31 Two flow diagrams of precompaction arrangements for roller presses [B.48] Fig. 6.8-32 Salt briquettes that are used for the regeneration of ion-exchange water softeners...

Zeolites are crystalline aluminosilicates materials that possess ordered and interconnected microporous channels with diameters ranging from 0.2-20 A. Their unique properties (microporosity, high surface area, acid-base character, shape) have made than a material of choice in a great number of applications. Zeohtes are intensively used in gas separation due to their ability to adsorb selectively a large variety of molecules and are also known as molecular sieves. Furthermore, these materials are also used as ion exchangers (water softeners) and catalysts in petrochonistry. Currently, the world s annual production of natural zeoUte is about 4 million tons. Of this quantity, 2.6 milUon tons are shipped to Chinese markets to be used in the concrete industry. The amount of synthetic zeohtes produced is about 1.5 miUion tons (Figure 5.1). 

Boiler feed water was treated by sand filtration using pressure filters, followed by ion-exchange water softening. Hardness was controlled at less than 0.5 ppm calcium carbonate (CaCOj). 

Three climeiisiotuil stniriiires Feldspar, one of the most abundant rock-forming minerals (note the formation of four-membered rings). Quartz, pure silica. (Note (he formation of helical chains which link to produce a three-dimensional array.) These minerals also include the zeolites (Figure 10.23) which are used as ion exchangers, water softeners and catalysts. ... 

---