Softening, base exchange

Indian Ion Exchange and Chemical Industries - Produces reverse osmosis and demineralization systems, base exchange softeners, clarifiers and filters, degassers and de-aerators, filtration and micro filtration systems, effluent treatment plant...http //www.indianionexchange.com. ... 

Sodium cycle softening (base-exchange softening) is used primarily to remove the risk of calcium- and magnesium-based crystalline scale formation and deposition. The general reaction is as shown in Figure 9.2. 

Where the feed contains a large proportion of treated water, softening is a minimum requirement and the raw water quality dictates whether a more sophisticated form of external treatment would be preferable. If the water has a high alkalinity it calls for de-alkalization and base exchange. De-ionization is the ideal water treatment, but is usually avoided if possible because of its cost and use of corrosive chemicals. Membrane processes giving partial de-ionization are not normally installed at present, but are certain to become important in the future. 

The operation of a base exchanger is chemically inefficient, and the spent regenerant contains large amounts of excess salt which may occasionally be difficult to dispose of. Factory softeners make a major contribution to the chloride content of the UK s industrial rivers, and in the longer term there will be heavy pressure from environmentalists to reduce the amount of salt being discharged. 

Hardness breakthrough with ion-exchange (base exchange, BX) softening NOTE Caused by Fe/Mn fouling, resin breakdown/loss, or inadequate regeneration. Increased risk of carbonate scale or phosphate sludge Loss of alkalinity and hence an increased silica deposition risk... 

Replacement of positive ions of a soluble salt by passing sodium through a cation resin (softening or base exchange) or hydrogen through an acidic resin (as in one half of the demineralization process). 

AVT Barg BD BDHR BF BOF BOOM BOP BS W BSI BTA Btu/lb BW BWR BX CA CANDUR CDI CFH CFR CHA CHF CHZ Cl CIP CMC CMC CMC COC All-Volatile treatment bar (pressure), gravity blowdown blowdown and heat recovery system blast furnace basic oxygen furnace boiler build, own, operate, maintain balance of plant basic sediment and water British Standards Institution benzotriazole British thermal unit(s) per pound boiler water boiling water reactor base-exchange water softener cellulose acetate Canadian deuterium reactor continuous deionization critical heat flux Code of Federal Regulations cyclohexylamine critical heat-flux carbohydrazide cast iron boiler clean-in-place carboxymethylcellulose (sodium) carboxy-methylcellulose critical miscelle concentration cycle of concentration... 

Natural and artificial permutites, such as analcime Na[AlSi206]H20, belong also to the zeolites, in which base exchange occurs, for example Ca2+ for Na+ (water softening). The organic permutites, so important nowadays in ion exchange, have the open structure in common with these silicates. 

Cans, at the turn of the 19lh century, synthesised aluminosilicate materials capable of water softening. He called them Permutits and for many years they were employed as domestic and industrial water softeners, as well as in the treatment of nuclear waste. This, together with the first identification of base exchange in soils (Way [2] and Thompson [3 J), led to the misunderstandings perpetuated in elementary texts that zeolites are responsible for the ion-exchange in soils, and that they are widely used as water softeners. In truth the clay minerals contribute mainly to the ability of soils to take up cations, such as ammonium, and Permutits were amorphous materials with low cation exchange capacities and limited chemical stability. 

At that time there were synthetic zeolites used for softening water by base exchange. These were amorphous sodium aluminosilicates. Active cracking catalysts were made from them by exchanging the sodium ions with other ions. 

ZeoHte-based materials are extremely versatile uses include detergent manufacture, ion-exchange resins (ie, water softeners), catalytic appHcations in the petroleum industry, separation processes (ie, molecular sieves), and as an adsorbent for water, carbon dioxide, mercaptans, and hydrogen sulfide. 

Most home water softeners are based on ion-exchange resins. The first ion-exchange materials used in softening water were naturally occurring polymeric aluminum silicates called zeolites. At present, synthetic zeolites are also used for this purpose. Today, most... 

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