Softening waters by ion-exchange method

RIGIDITY of WATER

Scum and adjournment of salts on home appliances (for example, in teapots),

film on tea etc. - all this parameters of rigid water. Use of such water

for the economic purposes causes a number of inconveniences. For example,

the charge of a soap is increased at washing, slowly boil soft meat and

vegetables, service life of home appliances decreases. Interrelation of

rigidity of water and education of stones in kidneys now is known.

The rigidity of drinking water under the working standards should be not

higher 7 mg-ecv/g, and only in the special cases it is

supposed up to 10 mg-ecv/g. For the industrial purposes use of rigid water

is inadmissible.

The general rigidity of water is a set of properties caused by the contents

in it ions of magnesium and calcium.

Hard water must be soften before use.

The first way – reagent method i.e., addition slaked to exhaust and soda

Na2CO3 (a limy way), addition of polyphosphates.

The second way - application of cationits , i.e., synthetic ion-exchange

pitches (filtering).

Ion-exchange pitches

These are substances capable to an ionic exchange at contact to solutions

of electrolits. Ionic-exchange clearing allows to take and utilize a wide

spectrum of polluting substances: heavy metals, chrom, nitrates and

nitrites, cyanic connections, radioactive substances, and also умягчает and

unironing water. Thus the high degree of clearing (up to a level of maximum

concentration limit) is reached. Except for that ionits are used for

unsalting waters during water-preparation. Inorganic and organic ionits can

be natural (for example: zeolites, cellulose, peat, wood) and synthetic

(silica gel and the most important ion-exchange pitches). Depending on a

degree dissociation of ion-exchange pitches can be strong and weak.

Depending on a sort of ions which are connected to active groups of ionits,

distinguish the following its form: for cationits - the hydrogen form (H-

form) and the salt form, when active groups are connected to ions of metals

(for example, Na-form, NH4-form), for anionits OH-form, Cl-form, etc.

Ability of ionits to a full exchange is characterized by exchange capacity

which is equal to number of its active groups participating in an exchange.

For the quantitative characteristic of ion-exchange properties of ionits

usually define their dynamic and sometimes full (general) exchange capacity

(static). Main requirements to ionits, used for water treating: high

exchange capacity, high speed of an ionic exchange, sufficient stability in

relation to acids, alkalis, oxidizers and reducers, insolubility in water,

organic solvents and solutions of electrolits and limited swelling

capacity. In water-preparation in a conditions of life are frequently used

high-acid cationits domestic and import manufacturers mainly for softening

and iron removal of waters. An example: the structure of cationits can be

expressed formula Na2R, where Na+ - rather mobile cation. If to pass hard

water through layers of cationits ions of sodium exchange on ions of

calcium and magnesium:

Ca 2 + + Na2R = 2Na + + CaR

Mg 2 + + Na2R = 2Na + + MgR

Thus ions Ca2+ and Mg2+ pass from a solution to cationit, and ions Na+-from

cationit in a solution, and rigidity is eliminated. After pauperization of

cationit ions of Na+ cationits usually recycle. Them maintain in solution

NaCl where there is a return replacement - ions Na+ pass in cationit, and

ions Ca2+ and Mg2+ - in a solution:

CaR + 2Na+ = Na2R + Ca 2+

MgR + 2Na + = Na2R + Mg 2+

After that regenerated cationit can be used for mitigation of new portions

of hard water. The degree of regeneration is influenced with type of

ionits, structure of the sated layer, the nature, concentration and a

solution of recycling substance, temperature, time of contact and the

charge of reagents. Restoration of exchange capacity at regeneration

usually makes 60 - 100 %.

Kinds of rigidity

General rigidity. It is defined by total concentration of ions of calcium

and magnesium. Represents the sum of carbonate (time) and uncarbonate

(constant) rigidity.

Carbonate rigidity. It is caused by presence in water of hydrocarbonates

and carbonates (at рН> 8.3) calcium and magnesium. The given type of

rigidity almost completely is eliminated at boiling waters and consequently

refers to as time rigidity. At heating water hydrocarbonates break up with

formation of a coal acid and settling out of a carbonate of calcium and

oxyhydroxide of magnesium.

Uncarbonate rigidity. It is caused by presence calcium and magnesian salts

of strong acids (the chamois, nitric, hydrochloric) and at boiling it is

not eliminated (constant rigidity).

Origin of rigidity

Ions of calcium (Ca2+) and magnesium (Mg2+), and also others alkali-

ground metals causing rigidity, are present at all mineralizeed waters.

Their source are natural deposits of limestones, plaster and dolomite. Ions

of calcium and magnesium act in water as a result of interaction dissolved

dioxide of carbon with minerals and at other processes of dissolution and

chemical aeration of rocks. As a source of these ions, the microbiological

processes proceeding in soil on the area of a reservoir can serve in ground

adjournment, and also sewage of the various enterprises also.

Rigidity of water changes over a wide range and there is a set of

types of classifications of water on a degree of its rigidity. Usually in

little mineralizeed waters prevails (up to 70%-80 %) the rigidity caused by

ions of calcium (though in separate rare cases magnesian rigidity can

reach(achieve) 50-60 %). With increase in a degree of a mineralization of

water the contents of ions of calcium (Са2+) quickly falls and seldom

exceeds 1 g/l. The contents of ions of magnesium (Mg2+) in high

mineralizeed waters can reach several grammes, and in salty lakes - tens

grammes on one litre of water.As a whole, rigidity of superficial waters,

as a rule, is less than rigidity of waters underground. Rigidity of

superficial waters is subject to appreciable seasonal fluctuations,

reaching usually the greatest value at the end of winter and the least

during a high water when it is plentifully diluted soft rain and thawed

snow. Sea and ocean water have very high rigidity (tens and hundreds in mg

- ecv/l)

Influence of rigidity

From the point of view of application of water for drinking needs, its

acceptability on a degree of rigidity can vary essentially depending on

local conditions. The threshold of taste for an ion of calcium lays (in

recalculation on a mg - equivalent) in a range of 2-6 mg - ecv/l, depending

on corresponding of anionits, and a threshold of taste for magnesium and

than that is lower. In some cases water is comprehensible to consumers with

rigidity above 10 mg-ecv/l. High rigidity worsens organoleptic properties

of water, giving to it bitterish taste and having negative an effect on

bodies of digestion.

The world Organization of Public health services (CART) does not offer any

recommended size of rigidity under indications of influence on health. In

materials the CART is spoken that though a number of researches and has

revealed statistically inverse relationship between rigidity of potable

water and the cardiovascular diseases, the available data are not

sufficient for a conclusion about causal character of this communication.

Similarly, unequivocally it is not proved, that soft water renders a

negative effect on balance of mineral substances of an organism of the

person

At the same time, depending on рН and alkalinity, water with rigidity of

4 mg-ecv/l can above cause in distributive system

adjournment of slags and scums (a carbonate of calcium), is especial at

heating. For this reason norms of Boiler inspection enter very rigid

requirements to size of rigidity of the water used for a meal of boilers

(0.05-0.1 mg-ecv/l). Besides at interaction of salts of rigidity with

washing substances (the soap, detergent powders, shampoos) occurs formation

of "soap slags" as foam. It results not only in the significant

overexpenditure of washing-up liquids. Such foam after drying remains as a

strike on the sanitary technician, linen, a human skin, on hair (unpleasant

feeling of "rigid" hair well-known to much). The main negative influence of

these slags on the person is that they destroy a natural fatty film with

which the normal skin is always covered and hammer its time. An attribute

of such negative influence is characteristic "scratch" of cleanly washed up

skin or hair. It appears, that the irritation causing in some people

feeling "soapiness" after using soft water is an attribute of that the

protective fatty film on a skin is whole and safe. It also slides.

At the same time, it is necessary to mention and other side of a medal.

Soft water with rigidity less than 2 mg-ecv/l has low buffer capacity

(alcalinity) and can, depending on a level рН and of some other factors,

render the increasedcorrosive attack to water pipes. Therefore, in a number

of applications (it is especial in the heating engineer) sometimes it is

necessary to carry out special processing of water with the purpose of

achievement of an optimum ratio between rigidity of water and its corrosion

activity.

EXPERIMENTAL PART

The adsorption processes including both processes cleanly including

physical, and the processes conducting to formation of new chemical

substances are rather various. Processes concern to them ion-exchange

chromatographies proceeding between ionits and solutions of electrolit

also.

Due to the universality and these processes have found of flexibility

wide application in analytical chemistry, food and an iron and steel

industry, in power system, water-preparation and in many other areas of a

science and technics(technical equipment), and now supersede from an

industrial practice other methods sorption [1-3]. Despite of the big

assortment industrial ionits, the majority of them, especially,

condensation type differ such low parameters, as low speed sorption, small

stability to thermal, chemical influences, etc. It limits opportunities and

spheres of their application [4,5].

By us it is received new monofunctional sulphocationite on the basis of

interaction of styrene with an accessible and cheap waste of agricultural

and cotton scraping industries.

[pic]

Sorption abilities of sulphocationite to ions of calcium, magnesium,

copper, nickel carried out research from 0.1N solutions of СаСl2, MgCl2,

CuSO4 and NiSO4. Sorption of calcium and magnesium determined by

trilonometric, copper by iodometric, nickel by photocolorimetric methods

[10,11].

According to the literary data, polymers and ion-exchangers, received

on the basis of derivatives of furan differ from raised thermal and

chemical stability and mechanical durability [5,6]. The basic properties of

received sulphocationite are submitted in table 1.

Table 1

The main physical and chemical parameters of received sulphocationite

|№ |Parameters |Values |

|1.|Bulk weight, g/ml |0.68 |

|2.|Specific volume of bulk cationit in Н-form, ml/g |3.5 |

|3.|Static exchange capacity, in mg - ecv/g, on: | |

| |0.1N. solution of NaOH |5,2 |

| |0.1N. solution of NaCl |4.5 |

| | |Nа-form |4.8 |

| | |Nа-form |3.8 |

| | |Nа-form |3.0 |

| | |Nа-form |2.34 |

|4.|Mechanical durability |99 % |

As is known in many regions of our republic used in a life and on

manufacture water has high rigidity which sometimes reaches up to 12 mg-

ecv/l instead of 2874-82 "Potable water" received according to GOST – 2.5-7

mg-ecv/l.

From the data of table 1 it is visible, that the examinee cationit

possesses high enough parameters of size of exchange capacity on ions of

calcium and magnesium. As object of research we had been used artesian

water of area Shurchi in Surkhan-Darya area which has rigidity of 12.2 mg-

ecv/l. Cationits tested in Н-and Na-forms.

1 gr. of cationit filled in 200 ml of researched water. In 24 hours

water separated from cationit and determined its rigidity trilonometric

method at the presence of the indicator chromogen black. Thus rigidity of

water in the Н-form has made 4.5 mg - ecv/l, and in the Na-form of 2.2 mg -

ecv/l.

Except for it we had been carried out researches on softening water of

2.5 mg-ecv/l having rigidity. After contact within 6

hours of water with cationit rigidity of it corresponded at use cationit

in:

the Н-form – 0.8 mg-ecv/l;

the Na-form – 0.4 mg-ecv/l.

Results of the received researches testifies to perspectivity of work

with the examinee with sulphocationite.

Vocabulary

|Adjournment |––– |Отложения |

|Artesian water |––––|Артезианская вода |

|Cationit |––––|Катионит |

|Anionit |––––|Анионит |

|Sorption |––––|Сорбция |

|Sulphocationite |––––|Сульфокатионит |

|Rigidity |––––|Жесткость |

|Indicator chromogen black |––––|Индикатор хромоген черный |

|Thrilonometric |––––|Трилонометрический |

|Bulk weight |––––|Насыпной вес |

|Condensation |––––|Конденсация |

|Hydrocarbonate |––––|Гидрокарбонат |

|Slag |––––|Шлак |

|Scum |––––|Накипь |

|Ionits |––––|Ионит |

|Alkalinity |––––|Щелочность |

|Softening |––––|Умягчение |

|Calcium |––––|Кальций |

|Magnesium. |––––|Магний |

|Sewage |––––|Сточные воды |

|Corrosion activity |––––|Деятельность коррозии |

|Static exchange capacity |––––|Статическая обменная емкость |

|Swelling capacity |––––|Влажность |

|Iodometric, |––––|Иодометрический |

|Photocolorimetric |––––|Фотокалориметрический |

|Chemical stability |––––|Химическая устойчивость |

|Thermal stability |––––|Термическая устойчивость |

|Reagent method |––––|Реагентный метод |

|Potable water | |Питьевая вода |

|Cotton scraping industries | |Хлопчатоочистительная пром. |

|Polycondensation | |Поликонденсация |

|Correspond | |Переписываются |

|Сopper | |Медь |

|desorption | |Десорбция |

|Potentiometric titration | |Потенциометрич. титрование |

|Flexibility | |Гибкость |

|Specific volume | |Удельный объем |

Литература

1. Полянский Н.Г. Сб. Синтез и свойства ионообменных материалов», М.:

«Наука»,1968г.

2. Либинсон Г.С. Физико-химические свойства карбоксильных катионитов, М.:

«Наука», 1969.

3. Гельферих Ф. «Иониты»,М.: Изд. ИЛ., 1962 г.

4. Таджиходжаев З.А. Разработка ионообменных и композиционных материалов

многофункционального назначения на основе вторичных продуктов производств

и технологии их получения».: Автореф. дисс. доктора технических наук. «,

Ташкент.: 2002.

5. Муталов Ш.А., Турсунов Т., Назирова Р.А. Исследование сорбции ионов

цветных металлов слабоосновными анионитами поликонденсационного типа./Ж.

Композиционные материалы. № 2, С.7-8. Ташкент:. 2003.

6. Таджиходжаев З.А., Джалилов А.Т. Синтез и исследование свойств

катионообменных смол на основе вторичных продуктов химических

предприятий.// Ж. Прикл. химии. 1998. т. 72. № 9. С. 1578-1580.

7. Гриссбах Р. «Теория и практика ионного обмена», М.: Изд. ИЛ. 1963.,

с. 303 – 310.

8. Л.Беллами «Инфракрасные спектры сложных молекул», М.: ИЛ, 1963г.

9. Алексеев В.Н. «Количественный анализ», М.: Химия, 1972г.

10. Пешкова В.М., Громова М.И. Практическое руководство по

спектрофотометрии и калориметрии. М.: Изд.«Московского Университета», 1965

г.

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...

CH2

CH=CH2

...

CH2

CH=CH2

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МЕНЮ

Softening waters by ion-exchange method

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