process asgnmnt

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1. Ion exchange is an exchange ofionsbetween twoelectrolytesor between an

electrolytesolutionand acomplex. In most cases the term is used to denote the processes of

purification, separation, and decontamination of aqueous and other ion-containing solutions with

solidpolymericormineralic'ion exchangers'.

Typical ion exchangers areion exchange resins(functionalized porousorgelpolymer),zeolites,montmorillonite,clay, andsoilhumus. Ion exchangers are eithercation

exchangers that exchange positivelychargedions (cations) oranion exchangers that exchange

negatively charged ions (anions). There are alsoamphotericexchangers that are able to exchange both

cations and anions simultaneously. However, the simultaneous exchange of cations and anions can be

more efficiently performed in mixed beds that contain a mixture of anion and cation exchange resins, or

passing the treated solution through several different ion exchange materials.

2. The adsorption of the molecules to the solid support is driven by the ionic interaction between the

oppositely charged ionic groups in the sample molecule and in the functional ligand on the

support. The strength of the interaction is determined by the number and location of the chargeson the molecule and on the functional group. By increasing the salt concentration (generally by

using a linear salt gradient) the molecules with the weakest ionic interactions start to elute from

the column first. Molecules that have a stronger ionic interaction require a higher salt

concentration and elute later in the gradient. The binding capacities of ion exchange resins are

generally quite high.

3. Ion exchangers are resins that are polymers with cross-linking ( connectionsbetween long carbon chains in a polymer ). The resin has active groups in the

form of electrically charged sites. At these sites, ions of opposite charge are

attracted but may be replaced by other ions depending on their relative

concentrations and affinities for the sites. Two key factors determine theeffectiveness of a given ion exchange resin: favorability of any given ion, and

the number of active sites available for this exchange. To maximize the active

sites, significant surface areas are generally desirable. The active sites are one

of a few types of functional groups that can exchange ions with either plus or

minus charge. Frequently, the resins are cast in the form of porous beads.

Cross-linking, usually on the order of 0.5 to 15 percent, comes from adding divinyl

benzene to the reaction mixture during production of the resin. The size of the

particles also plays a role in the utility of the resin. Smaller particles usually are more

effective because of increased surface area but cause large head losses that drive uppump equipment and energy costs. Temperature and pH also affect the effectiveness

of ion exchange, since pH is inherently tied to the number of ions available for

exchange, and temperature governs the kinetics of the process. The rate-limiting step

is not always the same, and temperature's role is still not thoroughly understood.
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Regeneration of the resin is also a feauture of ion exchange. The resin is flushed free

of the newly-exchanged ions and contacted with a solution of the ions to replace them.

Regeneration is initiated after most of the active sites have been used and the ion

exchange is no longer effective. With regeneration, the same resin beads can be used

over and over again, and the ions that we are looking to get out of the system can be

concentrated in the backwash effluent, which is just a term for the spent fluid used toregenerate the ion exchanger.

Summary:

APPLICATION IN CHEMICAL INDUSTRIES

on exchange is widely used in the food & beverage, hydrometallurgical, metals finishing, chemical &petrochemical, pharmaceutical, sugar & sweeteners, ground & potable water, nuclear, softening &

industrial water, semiconductor, power, and a host of other industries.

Most typical example of application is preparation of high purity water forpower engineering, electronic

and nuclear industries; i.e.polymericormineralicinsolubleion exchangers are widely used forwater

softening,water purification, waterdecontamination, etc.

Ion exchange is a method widely used in household (laundry detergentsandwater filters) to producesoft

water. This is accomplished by exchangingcalciumCa2+

andmagnesiumMg2+

cations against Na+

or

H+

cations (seewater softening). Another application for ion exchange in domestic water treatment is the

removal ofnitrateandnatural organic matter.

Industrial and analyticalion exchange chromatographyis another area to be mentioned.Ion exchange

chromatographyis achromatographicalmethod that is widely used for chemical analysis and separation

of ions. For example, inbiochemistryit is widely used to separate charged molecules such asproteins.

An important area of the application is extraction and purification of biologically produced substances

such as proteins (amino acids) andDNA/RNA.

Ion-exchange processes are used to separate and purifymetals, including

separatinguraniumfromplutoniumand otheractinides, includingthorium,

andlanthanum,neodymium,ytterbium,samarium,lutetium, from each other and the otherlanthanides.

There are two series ofrare earthmetals, the lanthanides and the actinides, both of whose families all

have very similar chemical and physical properties. Using methods developed byFrank Speddingin the

1940s, ion-exchange used to be the only practical way to separate them in large quantities, until the

advent of solvent extraction techniques that can be scaled up enormously.

A very important case is thePUREXprocess (plutonium-uranium extraction process), which is used to

separate theplutoniumand theuraniumfrom the spent fuel products from anuclear reactor, and to be

able to dispose of the waste products. Then, the plutonium and uranium are available for making nuclear-

energy materials, such as new reactor fuel andnuclear weapons.
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The ion-exchange process is also used to separate other sets of very similar chemical elements, such

aszirconiumandhafnium, which is also very important for the nuclear industry. Zirconium is practically

transparent to free neutrons, used in building reactors, but hafnium is a very strong absorber of neutrons,

used in reactorcontrol rods.

Ion exchangers are used innuclear reprocessingand the treatment ofradioactive waste.

Ion exchange resins in the form of thinmembranesare used inchloralkali process,fuel

cellsandvanadium redox batteries. Ion exchange can also be used to remove hardness from water by

exchanging calcium and magnesium ions for sodium ions in an ion exchange column.

Liquid (aqueous) phase ion exchangedesalinationhas been demonstrated.[1]

In this technique anions

and cations in salt water are exchanged for carbonate anions and calcium cations respectively using

electrokinetic shockwaves. Calcium and carbonate ions then react to formcalcium carbonate, which then

precipitates leaving behind fresh water. The desalination occurs at ambient temperature and pressure

and requires no membranes or solid ion exchangers. Theoretical energy efficiency of this method is on

par withelectrodialysisandreverse osmosis.

WATER SOFTENING PROCESS MECHANISM

as ion trade and this filters the onerous substances such as magnesium and calcium found

within the water while changing it with an equal amount of salt. Thus the calcium salts are

replaced with sodium salts with the assistance of aWater Softener Reviewsand one should

do not forget that an environment friendly Water Softening will leave behind much less salt.

The change will be measured with the assistance of TDS meter.However, a Water Softener shouldnt be installed in case you are beneficial with a sodium

restricted diet. But then, I would recommend installing a Water Softener if the necessity

arrives for the appliance after which you may remove the salt and different adulterations by

inserting a unit.

Water Softening additionally removes tiny quantities of iron from the water but it increases

the salt left behind and the salt used. When there may be a large amount of iron present in

water its going to result in extreme salt use which eventually will smash the mattress of the

Water Softener. So you should avoid utilizing Water Softening as the primary method for

reducing iron in water.

For large-scale municipal operations, a process known as the "lime-soda process" is

used to remove Ca2+ and Mg2+ from the water supply. Ion-exchange reactions, similar

to those you performed in this experiment, which result in the formation of an
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insoluble precipitate, are the basis of this process. The water is treated with a

combination of slaked lime, Ca(OH)2, and soda ash, Na2CO3. Calcium precipitates as

CaCO3, and magnesium precipitates as Mg(OH)2. These solids can be collected, thus

removing the scale-forming cations from the water supply.

To see this process in more detail, let us consider the reaction for the precipitation ofMg(OH)2. Consultation of the solubility guidelines in the experiment reveals that the

Ca(OH)2 of slaked lime is moderately soluble in water. Hence, it can dissociate in

water to give one Ca2+ ion and two OH- ions for each unit of Ca(OH)2 that dissolves.

The OH- ions react with Mg2+ ions in the water to form the insoluble precipitate. The

Ca2+ ions are unaffected by this reaction, and so we do not include them in the net

ionic reaction (Equation 2). They are removed by the separate reaction with CO32- ions

from the soda ash.

(2)

Household water softeners typically use a different process, known as ion exchange.

Ion-exchange devices consist of a bed of plastic (polymer) beads covalently bound to

anion groups, such as -COO-. The negative charge of these anions is balanced by

Na+ cations attached to them. When water containing Ca2+ and Mg2+ is passed through

the ion exchanger, the Ca2+ and Mg2+ ions are more attracted to the anion groups than

the Na+ ions. Hence, they replace the Na+ ions on the beads, and so the Na+ ions

(which do not form scale) go into the water in their place.


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Figure 1

When hard tapwater passes through the ion exchanger (left),the calcium ions from the tapwater replace the sodium ions in

the ion exchanger. The softened water, containing sodium ions

in place of calcium ions, can be collected for household use.

Unfortunately, many people with high blood pressure or other health problems must

restrict their intake of sodium. Because water softened by this type of ion exchange

contains many sodium ions, people with limited sodium intakes should avoid drinking

water that has been softened this way. Several new techniques for softening water

without introducing sodium ions are beginning to appear on the market.

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