Water Hardness

Water Hardness

Name : MAZADUL HASAN SHESHIRID: 2010000400008Batch: 13th Batch (Session 2009-2013)Department: Wet Processing Technology Email: [email protected]: www. Textilelab.blogspot.com Southeast UniversityDepartment of Textile Engineering

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Generally soaps create foam in water, but in present of some materials the foam creation is reduced and need more soap for producing foam, and this condition of water is called water hardness.

The presence of Calcium, Magnesium salt i.e. bicarbonates, sulphates, chloride in water is called causes of hardness of water. The water which contains these salts is called hard water. Hard water does not easily form lather with soap as the salt of Calcium and Magnesium react with soap to form insoluble organic salts.

CaSO4 + 2RCOONa → (RCOO)2Ca ↓ + Na2SO4

MgSO4 + 2RCOONa → (RCOO)2Mg ↓ + Na2SO4

WATER HARDNESS

WATERThe major concern for any kind of wet process industry is ‘Water’ because it is the quality of water which determines the quality of dyeing. Water quality generally vary in different areas, also depends on the level or height of water level beneath the ground. In Narayangonj water level is around 130-140 ft but Knit Concern dyeing water is lifted from about 600 ft deep by submergible pumps.

Quality of Water found in the raw water here – total Hardness – 250-300 ppmpH – 8-9TDS – 2000-3000 ppm

SECTION HARDNESS IRON CONTENT TDS pH

Knit dyeing - <70 0.02 ppm <500 6.5-7

Yarn dyeing - <50 0.02 ppm <500 6.5-7

Quality of water required for Dyeing:

WATER

Reasons of water hardness

1. Temporary hardness:

Ca(HCO3)2, Mg(HCO3)2, Fe(HCO3)2

2. Permanent hardness:

CaCl2, CaSO4, Ca(NO3)2,

MgCl2, MgSO4, Mg(NO3)2

TYPES/ CLASSIFICATION OF HARDNESS

1. Temporary hardness.

2. Permanent hardness.

1. Temporary Hardness: Temporary hardness is due to the presence of bi-carbonates of

calcium and magnesium. This type of hardness is called temporary hardness. Because it can

be removed by easy means like boiling. When temporary hard water is boiled, the

carbonates decompose with liberation of carbon-dioxide and precipitation of the

insoluble Carbonates which are reformed.

MgCO3 is slightly soluble in water but heating will cause its hydrolysis into the much less soluble Mg(OH)2.

MgCO3 + H2O → Mg(OH)2 + CO2So simple boiling and filtering of water remove temporary hardness.

Ca(HCO3)2 CaCO3 ↓ + CO2 + H2O

Mg(HCO3)2 MgCO3 ↓ + CO2 + H2O

TEMPORARY HARDNESS

2. Permanent Hardness:

It is due to the presence of chlorides of Sulphates of Calcium and Magnesium. This

type of hardness is called permanent hardness. These salts do not decompose on

boiling. So permanent hardness can’t be removed easily. It can be removed by lime

when MgSO4 is responsible for hardness.

CaSO4 + Na2CO3 → Na2SO4 + CaCO3

MgSO4 + Na2CO3 → Na2SO4 + MgCO3

MgSO4 + Ca(OH)2 (Lime) → Mg(OH)2 + CaSO4

N.B. PH of drinking water is around 7 (Neutral)

PERMANENT HARDNESS

• German degree• French degree• American degree• British degree

Hardness Scales

UNITS OF HARDNESS

2. In degrees: The number of grains of Calcium carbonates which is present in 70,000 grains of water.Another unit of water hardness-3. GPG – Grains Per U.S. Gallon4. PP/ 1000005. GPG imperial – Grains Per British Gallon

Here,1 U.S. gallon = 8.33 pounds1 British gallon = 10 pounds (Used in our country)1 grain = 1/7000pound;i.e. 7000 grains = 1 lb

Hardness is expressed by-1. PPM (Parts Per Million)2. In degrees (Grains/ gallon)

1. PPM: The number of grains of calcium carbonates which is present in one million grains of water is called PPM.

1 grains of Calcium Carbonate present in 1 million grains water

1. 1º H (German) Hardness: 10 mg CaO in 1 litre of water

2. 1º H (French) Hardness: 10 mg CaCO3 in 1 litre of water

3. 1º H (English) Hardness: 10 mg CaCO3 in 0.7 litre of water

4. 1º H (American) Hardness: 1 mg CaCO3 in 1 litre of water

Definition of Different Hardness

Other scales for expressing water hardness -

• Parts per million (ppm): The number of parts of substances per million parts of water is known ppm. It is also called American hardness. It can be expressed by another way like mg/l or gm/m3.

• Grains per U.S. gallon (gpg): The number of grains of substances per 1 U.S. gallon of water (1 U.S. gallon of water weighs 8.33 pound) is known gpg.

• Parts per hundred thousand (pp/100,000): The number of parts of substances per 100,000 parts of water is known pp/100,000.

• Grains per imperial gallon (gpg imp): The number of grains of substances per 1 British imperial gallon of water (1 imperial gallon of water weighs 10.0 pound) is known gpg imp.

Relation of different scales -

1 ppm = 1.0 mg/l = 0.1 pp/100,000 = 0.0583 gpg (U.S.) = 0.07 gpg imp.

Scale Hardness

USA D GB F

1º USA 1.0 0.056 0.07 0.1

1º D 17.9 1.0 1.25 1.79

1º GB 14.3 0.8 1.0 1.43

1º F 10.0 0.56 0.7 1.0

Conversion factor of different water hardness scale

10dH = 17.90 American Hardness = 1.450 eH = 1.790 fH

10dH = 10 mg/ litre CaO= 7.4 mg/ litre MgO= 22.5 mg/ litre Ca(HCO3)2= 30 mg/ litre NaHCO3

Among the above the hardness which is expressed by the amount of NaHCO3 present in water is called alkaline hardness.

CLASSIFICATION OF WATER ACCORDING TO HARDNESS:

DESCRIPTION TOTAL HARDNESS

Very soft 0-40

Soft 5-80

Mild 9-140

Fairy hard 15-180

Hard 19-300

Very hard >300

From the above types of water, soft water with total hardness 5-80 is suitable for dyeing. In another cases like scouring we may use hard water.

Water hardness can also be noted as below: Upto 50 PPM → Water is very soft50 to 100 PPM → Water is moderately soft100 to 150 PPM → Water is slightly hard200 to 300 PPM → Water is hardAbove 300 PPM → Water is very hard

STANDARD/ QUALITY OF DYE HOUSE WATER

STANDARD FOR TEXTILE DYE HOUSE WATER SUPPLY/ SPECIFICATION FOR PROCESS WATER/ IDEAL QUALITY IF FEED WATER FOR TEXTILE INDUSTRY

MINIMUM STANDARD PERMISSIBLE CONCENTRATION

Color Colorless

Smell Odorless

PH value Nature (PH 7.8 )

Water hardness Less than 50 dH

Dissolved solids Less than 1 ml/L

Solids deposits Less than 50 mg/ L

Organic substances Less than 20 mg/ L

Inorganic salt Less than 500 mg/ L

Iron (Fe) Less than 0.1 mg/ L

Copper (Cu) Less than 0.005 mg/ L

Nitrate (NO3) Less than 50 mg/ L

Nitrite (NO2) Less than 5 mg/ L

Iron and copper are responsible for the creation of spots on fabric. For those spots we can use ‘spot removers’.

ESTIMATION OF WATER HARDNESS

Water hardness can be determined by the following 2 methods-

1. By titration with standard soap solution:

In this method total hardness/ permanent hardness can be measured.

2. By titration with HCl:

In this method temporary hardness can be measured.

ESTIMATION OF WATER HARDNESS

ESTIMATION OF TEMPORARY HARDNESS BY TITRATION BY TITRATION WITH HCL:

For determining temporary hardness 200cc hard water is taken into a 500 cc bottle. Then few drops of methyl orange is added in it as an indicator. Now titration is carried out by adding 0.1N cold HCl until the yellow color of methyl orange turns colorless.

Here, each meal 0.1N HCl is equivalent to 0.005 gm of CaCO3. The associated reactions are as follows:

Ca(HCO3)2+ 2HCl → CaCl2 + CO2 + H2O Mg(HCO3)2 + 2HCl → MgCl2 + CO2 + H2O

EXPRESSION:Multiplying the required amount of 0.1N HCl for

titration incc by –2.5 gives French hardness1.78 gives English hardness1.4 gives German hardness.Permanent hardness can be found by deducting the

temporary hardness from total hardness i.e.

Permanent hardness = Total hardness – Temporary hardness

Hardness rating ppm of CaCO3 (grains/US gallon) of CaCO3

Soft 0 to <75 0 to <5.2

Medium 75 to < 150 5.2 to <10.5

Hard 150 to < 300 10.5 to <21

Very hard 300 and above 21 and greater

Classification of water according to hardness

Problems causes by hard water in wet processing and their correction

Consequences of using hard water –

1. Precipitation of soaps;

2. Redeposition of dirt and insoluble soaps on the fabric being

washed – this can cause yellowing and lead to unlevel dyeing and

poor handle;

3. Precipitation of some dyes as calcium or magnesium salts;

4. Scale formation on equipments and in boilers and pipelines;

5. Reduction of the activity of the enzymes used in desizing;

6. Decrease solubility of sizing agents;

7. Coagulation of some types of print pastes;

8. Incompatibility with chemicals in finishing recipes

• Ca(HCO3)2 CaCO3 + CO2 + H2O• Mg(HCO3)2 MgCO3 + CO2 + H2O• MgCO3 + H2O Mg(OH)2 +CO2

(A) Problems in boiler

Scale thickness (mm) % heat loss (approx.)

1.00 10

3 17

5 22

10 30

20 43

Heat loss for pipe scaling

Parameter Acceptable limitAppearance Clear, without residueResidual hardness <5 ppmOxygen <0.02 mg/l Temporary CO2 0 mg/l Permanent CO2 <25 mg/l Iron <0.05 mg/l Copper <0.01 mg/l pH (at 25º C) 8.0 - 9.0 Boiler feed water temp. >90º C

Boiler feed water quality:

Wastage of soap (reaction with soap)

2 C17H35COONa + CaSO4 (C17H35COO)2Ca↓ + Na2SO4

Reaction with dyestuffs Reaction with dyes and lead dye wastage Sometimes it produces a duller shade

B) Problems in processing

DesizingDeactivate enzymes and makes it insolubilize some size materials like starch and PVA

Scouring

Combine with soap, precipitate metal-organic acids. Produce yellowing of off-white shades, reduce cleaning efficiency, and water absorption

Bleaching Decompose bleach baths

Mercerizing Form insoluble metal oxides, reduce absorbency and luster

How does the water hardness affect the textile processing?

Dyeing

Combine with dyes changing their shades, insoubilize dyes, cause tippy dyeing, reduce dye diffusion and hence results in poor washing and rubbing fastness.

Printing

Break emulsions, change thickener efficiency and viscosity, and those problems indicated for dyeing

Finishing

Interfere with catalysts, cause resins and other additives to become nonreactive, break emulsions and deactivate soaps

How does the water hardness affect the textile processing?

Estimation of water hardness

1. Using direct reading digital meter or strip 2. In laboratory it is usually determined by titration with a standardized

solution (e.g. Na-EDTA)

Basic principle:- Titration of sample water against standards (0.01M) EDTA solution

Preparation of 0.01M or 0.02N EDTA solution:Molecular weight of disodium salt of EDTA (CH2COOH)2 N2(CH2)2(CH2COONa)2.2H2O = (12+1*2+12+16*2+1)×2 + 14*2+(12+2)*2+ (12+1*2+12+16*2+23)×2 + 2*18= 118+ 28+28+162+36= 372

Estimation of total (permanent & temporary) hardness of supply water (by di-sodium salt of EDTA)

Therefore,In 1M solution of 1000ml contain 372 gm Na2-EDTAIn 0.01M solution of 1000ml contain 3.72 gm Na2-EDTAIn 0.01M solution of 100ml contain 0.372 gm Na2-EDTA

• Preparation of ammonia buffer solution:- 145ml of liquor ammonia (NH4OH) of specific gravity

0.88+15gm NH4Cl + distilled water to make 250ml solution to give a pH of 10.

Procedure:- Add 1ml of buffer solution (NH4OH+NH4Cl) to 100ml of the

original water sample. Add 3-4 drops of Eriochrome Black T indicator (0.2g dye in 15ml of triethanol amine + 5ml of ethanol)/ 1tablet (making powder) total hardness indicator.

- Titrate against 0.01M prepared EDTA solutions in burette until the color charges from wine red (or violet) to pure blue (or turquoise) with no reddish tone; then calculate the total hardness in terms of ppm of CaCO3.

Procedure:

TOTAL HARDNESS =

Volume of 0.01M EDTA solution in ml------------------------------------------------- × 1000 ppm of CaCO3.Volume of sample water in ml

Calculation:

Determination of temporary hardness of supply water

Basic principle:- This can be estimated by titration of sample water against standard solution of hydrochloric acid ( 0.05N HCl).

Preparation of 0.05N HCl:Molecular weight of HCL = 1 + 35.5 = 36.5& Equivalent weight of HCl = 36.5

Therefore,1000 ml of 1N HCl contain 36.5 gm HCl1000 ml of 0.05N HCL contain (36.5 x 0.05) or 1.825gm HClSo, 100 ml of 0.05N HCl contain 0.1825 gm HCl

Let, the concentration of diluted HCl is 35%, then35 gm HCl present in 100 ml of diluted HCl & 0.1825 gm HCl present in {(100 x 0.1825)/35} or0.528 ml diluted HCl

Procedure:- Add 1cc or 2 – 3 drop [from the solution of (0.1 gm solid methyl orange + 100cc distilled water)] methyl orange indicator to 100ml of fresh distilled water & titrate against 0.05N HCl. Let the titration reading be ‘a’ ml.

- Now titrate 100 ml of the sample water against 0.05N HCl using the same indicator (methyl-orange). Let the titration reading ‘b’ ml.

Observation:- Reading should be taken when the color of indicator change orange to red.Table I: Experimental data for reading ‘a’

Table II: Experimental data for reading ‘b’

Temporary hardness = 50(b-a) × 0.05 × 1000------------------------------ ppm (in terms of CaCO3)100

Calculation:

Preparation of 0.01M or 0.02N EDTA solution:Molecular weight of disodium salt of EDTA (CH2COOH)2 (N2CH2)2(CH2COONa)2.2H2O = (12+1*2+12+16*2+1)×2 + 14*2+(12+2)*2+ (12+1*2+12+16*2+23)×2 + 2*18= 118+ 28+28+162+36= 372

Therefore,In 1M solution of 1000ml contain 372 gm Na2-EDTAIn 0.01M solution of 1000ml contain 3.72 gm Na2-EDTAIn 0.01M solution of 100ml contain 0.372 gm Na2-EDTA

Determination of permanent hardness of supply water (by di-sodium salt of EDTA)

Preparation of ammonia buffer solution:- 145ml of liquor ammonia (NH4OH) of specific gravity 0.88+15gm NH4Cl + distilled water to make 250ml solution to give a pH of 10.

Procedure:- Take 100ml of sample water in a conical flask; boil it (around 30 minutes) to about 50 ml; cool and filter to remove bicarbonate residual (temporary hardness) and to expel carbon dioxide. Dilute it to by distilled water to make 100 ml. Add 2ml of ammonia buffer solution followed by one tablet of hardness indicator.

- Titrate against 0.01M prepared EDTA solutions from burette until the color charges from wine red (or violet) to pure blue (or turquoise) with no reddish tone; then calculate the hardness in terms of ppm of CaCO3.

Total hardness =

Volume of 0.01M EDTA solution in ml---------------------- --------------------------× 1000 ppm of CaCO3.Volume of sample water in ml

Calculation:

1. Lime-soda process

2. Base exchange process

3. Demineralization process

4. Sequestering agent

Methods for water softening

In this process hydrated lime and sodium carbonate is used to remove the hardness.

For temporary hardness – Ca(HCO3)2 + Ca(OH)2 2 CaCO3 + 2 H2OMg(HCO3)2 + Ca(OH)2 MgCO3 + CaCO3 + 2 H2OMgCO3 + Ca(OH)2 Mg(OH)2 + CaCO3

For permanent hardness – CaSO4 + Na2CO3 CaCO3 + Na2SO4MgCl2 + Ca(OH)2 CaCl2 + Mg(OH)2

CaCl2 form is removed by – CaCl2 + Na2CO3 2 NaCl + CaCO3

1. Lime-Soda process

In lime soda softening plant main parts are-1. Reagent tank (Soda lime + Coagulants)2. Reaction tank3. Filter4. Soft water storage tank.

The Plant:

PROCESSThe lime soda [Na2CO3 + Ca(OH)2] and coagulant (NaAlO2) are metered into the reaction tanks together with a predetermined amount of hard water. Agitation is brought about in every tank by a large propeller. When sufficient time has elapsed for the precipitation to be completed

the water passes through filters to the soft water storage.

THE RESULTBy this process we can produce soft water with 50-100 ppm. But if temperature and agitation are increased water with 5-20 ppm hardness can be obtained.

Lime-Soda process

Permutit process (Base/ Ion exchange method)

Permutit’ means exchange; in this process, hard water is treated with base exchange complex or Zeolites to remove the hardness of water. Zeolites are naturally occurring insoluble mineral of the sodium aluminosilicate type complex (e.g. NaAlSiO4. 3H2O ≈ Na-Permutit). This type of ion exchanger may produce artificially.

For temporary hardness –2Na-Permutit + Ca(HCO3)2 Ca-Permutit↓ + 2NaHCO3

For permanent hardness –2Na-Permutit + CaSO4 Ca-Permutit↓ + Na2SO42Na-Permutit + MgSO4 Mg-Permutit↓ + Na2SO42Na-Permutit + MgCl2 Mg-Permutit↓ + 2NaCl

Basic Principle

Regeneration of ZeolitesFor regeneration of sodium salt of the zeolite involves passing a concentrated solution (generally 10%) of NaCl through the exhausted zeolites.

Ca-Permutit + 2NaCl 2Na-Permutit + CaCl2

ADVANTAGES:1. By this process water can be softened up to 0-2 ppm, even zero

hardness can be obtained.2. Less floor space is required for machines.3. Here only one chemical is used and no objectionable chemical is

produced as by product.4. Here regeneration is possible and it is easy to carry out with CaCl

solution.


comes in contact with Zeolites, the water softened and soft water is collected from the downward outlet. When sufficient amount of hard water has passed then the supply of hard water is closed and then flow is reserved and beds of Zeolites and other substances are cleaned. Then the cleansed is regenerated by passing 10% NaCl through the Zeolites and the Zeolites are regenerated again.

PROCESSThe Zeolites are taken in the vessel as shown in figure with other required substances. When the hare ward is passed through the inlet,


Demineralization method

The newer synthetic polymer ion exchangers are much more versatile than the zeolites and are widely used for water softening and demineralization. They are often called ion exchange resins. This reagent can remove all mineral salts to complete demineralisation of hard water. It has two types of ion exchanger – Cation exchanger and Anion exchanger.

A) Cation exchange: Cation exchanger has replaceable H+ or Na+ ion. Cation exchange resins are

organic in nature (made up by polymerization of polyhydric phenols with formaldehyde. It is also manufactured by sulphonation of coal). These reagents replace the ions of hard water by hydrogen, leaving the water an equivalent amount of acids.

For temporary hardness – H2R + Ca(HCO3)2 CaR + 2H2CO3

H2CO3 CO2 + H2O

For temporary hardness – H2R + CaCl2 CaR + 2HClH2R + CaSO4 CaR + H2SO4

General reaction – 2(Polymer – SO3¯H+) (s) + Ca²+ (aq) ↔ (Polymer – SO3¯)2Ca²+ (s) + 2H+ (aq)

Cation exchange:

B) Anion exchange:Anion exchanger has replaceable OH¯ ion. In this unit acid is absorbed by the

anionic exchanger which displaces the anionic groups like Cl¯, SO4¯ ¯, from acids.

General reaction –2(Polymer – NR3+OH¯) (s) + 2Cl¯ (aq) ↔ 2(Polymer – NR3+Cl¯) (s) + 2HO¯ (aq)

• Water can be totally demineralised by firstly exchanging all cations using s strongly acid form of a cation exchanger. Thus a solution of salts M+X¯ becomes a solution of acid H+X¯, the M+ ions being retained by the resin. Subsequently a strongly basic form of an anion exchanger absorbs the X¯ ions and liberates OH¯ ions into water. These then neutralize the H+ ions from the first step. The reslt is retention of all anions and cations and the neutralization of H+ and OH¯ to form pure demineralization water.

• 2H+ (aq) + 2OH¯ (aq) ↔ 2H2O

Anion exchange:

1. Cation exchanger – (Polymer – SO3¯)2Ca²+ (s) + 2HCl ↔ 2(Polymer – SO3¯H+) (s) + Ca2Cl

2. Anionic exchanger – 2(Polymer – NR3+Cl¯) (s) + 2NaOH ↔ 2(Polymer – NR3+OH¯) (s) + 2NaCl

Regeneration of reagents:

Demineralization Treatment plant

Plant Description: Demineralization by Resin treatmentThree vessels system – Vessel – 1 – Multi-Grade Filter (MGF) – For Iron Removal Vessel – 2 – Activated Carbon Filter (ACF) – For TDS removal

Vessel – 3 – Softener Filter (SF -Resin) – For Hardness removal

Demineralization Treatment plant

Addition of a sequestering agent to the water avoids many problems from relatively low concentrations of undesirable metal ions.

Example –EDTA (ethylenediamine tetra-acitic acid), related aminocarboxylic

acids, polyphosphates such as 1. sodium tetrametaphosphate Na4P4O12, 2. Calgon -s3. Sodium hexametaphosphate Na6P6O18.

Sequestering Agents

Hard water can create so many problems during wet processing from desizing to finishing in textile mills. Since every process is related to the next process, so all processes should be done precisely to get best result. To do it first we have to know what problems hard water can create in different stage of textile processing.

Problems caused by hard water in textile industry

Process Problem

Scouring

Hard react with soap during scouring. Soap is the Na & K salt of higher fatty acid (C17H35COONa). The Hard water does not easily form lather by reacting with soap. The Ca & Mg salt of hard water reacts with soap and produce insoluble organic salts which becomes the wastage of soap.

CaSO4 + 2 C17H35COONa --> (C17H35COO)2Ca + Na2SO4 Insoluble organic salt

If we use hard water in wet processing, then they produce insoluble salt which is deposited with the fabric. As a result, the surface of scoured fabric become harsh, hard & non-flexible which creates problem in the next process like produced uneven dyeing.

Process ProblemMercerizing It forms insoluble metal acid, reduce absorbency and luster.

Dyeing

Ca2+ and Mg2+ ions of hard water react with dye molecules and precipitated the dye. As a result dyestuff are spoilt. Hence, uneven shade (depth of dyeing) of color is produced.

Printing

It break the emulsion, change its thickness and efficiency and it is also harmful for thickener. Hard water cause problems in printing process like dyeing.

Finishing

Hard water interferes with catalysts, cause resins and other additives to become non reactive, break emulsion and datives soap.

Bleaching Hard water decompose bleach bath.H2O2 --> H2O + [O]

DesizingHard water de-active enzymes & insolubilize size materials such as starch, PVA etc.

Potential Problems Caused by Hard Water in Textile Wet Processing:In Boiler If hard water is used in boiler, then a layer is formed on the inner surface of the

vessel or in the inner side of tube. This layer is very hard just like as stone which is not removed without hammer or chesser or tessel. This is called scale. In boiler, temporary hard water produce CaCO3 & Mg(OH)2, the combination of CaCO3 & Mg(OH)2 is called scale.

Ca(HCO3)2 --> CaCO3 + CO2 + H2OMg(HCO3)2 --> Mg CO3 + CO2 + H2O

MgCO3 + H2O --> Mg(OH)2 + CO2[CaCO3 + Mg(OH)2 ] --> Scale.

As a result, in boiler more heat will be needed & for that, more fuel will be required. For scale formation, equally heat transformation in boiler tube is not possible very often. As a result, for excess heat of a particular part of the tube, the tube may burst.Heat loss of tube up to 40% according to the diameter of the tube. Heat loss by pipe scaling up to 40% for 20 mm scale.

SCALE THICKNESS HEAT LOSS1 mm approximately 10%3 mm „ 17%5 mm „ 22%10 mm „ 30%20 mm „ 43%

Corrosion can be a serious problem in boiler, if hard water is used in it. Dissolved O2 in the presence of CO2 is the common cause of corrosion. Fe present in hard water reacts with CO2 to form Fe CO3, which is the main process of corrosion. This Fe CO3 is hydrolyzed & produce Fe(OH)2, this agent / component damage the boiler.

Fe + H2O + CO2 --> Fe CO3 + H2OFe CO3 + H2O --> Fe(OH)2 + CO2

Here some reasons are described which are responsible for various problems on Dyeing or the problems associated with hard water on the fabric or Textile yarn.

Potential Problems Caused by Hard Water in Textile Wet Processing:Wastage of Soap & Detergent

Ca and Mg salt react with soap and lather is not formed easily. The reaction of it is-1. ( R-COO)2Ca + Na2SO4 ------> R-COONa + CaSO42. ( R-COO)2Ca + Mg2SO4 ------> (R-COO)2Mg + CaSO43. 2R-COONa + Mg2SO4 ------> (R-COO)2Mg + Na2SO4

Reaction with Dyestuff

The reactive groups present in dyes, react with Na, Ca, Mg, Fe of hard water. This causes wastages of dye, produces duller shade and faulty dyeing. Sequestering agent is added to prevent it.

Deposition on Textile Material

Soap reacts with hard water and produces insoluble salts which deposit on the fabric during scouring. These salts do hard and un-flexible the fabric.

Corrosion of Boiler In boiler, CO2 reacts with the iron (in presence of dissolved O2), forming FeCO3 which hydrolyses to Fe(OH)2. FeCO3 + H2 ------> Fe + H2O + CO2 Fe(OH)2 +CO2------->FeCO3 + H2O

Heat Loss Due to scale in the pipe, fuel consumption increases, thus heat loss is occurred. Again scale formation reduces thermal conductivity. Local overheating under the scale causes softening and ultimate tube failure.

Education

Water Hardness