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Water Hardness

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.

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Water Hardness

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  1. Water Hardness

  2. PREPARED BY ©right Name : MAZADUL HASAN SHESHIR ID: 2010000400008 Batch: 13th Batch (Session 2009-2013) Department: Wet Processing Technology Email: mazadulhasan@yahoo.com Blog: www. Textilelab.blogspot.com Southeast University Department of Textile Engineering

  3. WATER HARDNESS 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. 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. bicarbonates, sulphates, CaSO4 + 2RCOONa → (RCOO)2Ca ↓ + Na2SO4 MgSO4 + 2RCOONa → (RCOO)2Mg ↓ + Na2SO4

  4. WATER WATER The 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 pH TDS – 250-300 ppm – 8-9 – 2000-3000 ppm Quality of water required for Dyeing: SECTION HARDNESS IRON CONTENT TDS <500 pH Knit dyeing - <70 0.02 ppm 6.5-7 Yarn dyeing - <50 0.02 ppm <500 6.5-7

  5. Reasons of water hardness TYPES/ CLASSIFICATION OF HARDNESS 1. Temporary hardness. 2. Permanent 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

  6. TEMPORARY 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. Ca(HCO3)2 CaCO3 ↓ + CO2 + H2O Mg(HCO3)2 MgCO3 ↓ + CO2 + H2O 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 + CO2 So simple boiling and filtering of water remove temporary hardness.

  7. PERMANENT 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)

  8. Hardness Scales • • • • German degree French degree American degree British degree

  9. UNITS OF HARDNESS Hardness is expressed by- 1. 2. PPM (Parts Per Million) 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 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. Gallon 4. PP/ 100000 5. GPG imperial – Grains Per British Gallon Here, 1 U.S. gallon = 8.33 pounds 1 British gallon = 10 pounds (Used in our country) 1 grain = 1/7000 pound; i.e. 7000 grains = 1 lb

  10. Definition of Different Hardness 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

  11. 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.

  12. Relation of different scales - 1 ppm = 1.0 mg/l = 0.1 pp/100,000 = 0.0583 gpg (U.S.) = 0.07 gpg imp.

  13. Conversion factor of different water hardness scale 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

  14. 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.

  15. 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 soft 50 to 100 PPM → Water is moderately soft 100 to 150 PPM → Water is slightly hard 200 to 300 PPM → Water is hard Above 300 PPM → Water is very hard

  16. 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’.

  17. ESTIMATION OF WATER HARDNESS 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.

  18. 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 in cc by – 2.5 gives French hardness 1.78 gives English hardness 1.4 gives German hardness. Permanent hardness can be found by deducting the temporary hardness from total hardness i.e. Permanent hardness = Total hardness – Temporary hardness

  19. Classification of water according to 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

  20. 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

  21. (A) Problems in boiler • Ca(HCO3)2  CaCO3 + CO2 + H2O • Mg(HCO3)2  MgCO3 + CO2 + H2O • MgCO3 + H2O  Mg(OH)2 +CO2

  22. Heat loss for pipe scaling Scale thickness (mm) % heat loss (approx.) 1.00 10 3 17 5 22 10 30 20 43

  23. Boiler feed water quality: Parameter Acceptable limit Appearance Clear, without residue Residual hardness <5 ppm Oxygen <0.02 mg/l Temporary CO2 0 mg/l Permanent CO2 <25 mg/l Iron <0.05 mg/l Copper pH (at 25º C) <0.01 mg/l 8.0 - 9.0 Boiler feed water temp. >90º C

  24. B) Problems in processing 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

  25. How does the water hardness affect the textile processing? Deactivate enzymes and makes it insolubilize some size materials like starch and PVA Combine with soap, precipitate metal- organic acids. Produce yellowing of off- white shades, reduce cleaning efficiency, and water absorption Decompose bleach baths Desizing Scouring Bleaching Form insoluble metal oxides, reduce absorbency and luster Mercerizing

  26. How does the water hardness affect the textile processing? Combine with dyes changing their shades, insoubilize dyes, cause tippy dyeing, reduce dye diffusion and hence results in poor washing and rubbing fastness. Break emulsions, change thickener efficiency and viscosity, and those problems indicated for dyeing Dyeing Printing Interfere with catalysts, cause resins and other additives to become nonreactive, break emulsions and deactivate soaps Finishing

  27. 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)

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

  29. Therefore, In 1M solution of 1000ml contain 372 gm Na2-EDTA In 0.01M solution of 1000ml contain 3.72 gm Na2-EDTA In 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.

  30. Procedure: 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.

  31. Calculation: TOTAL HARDNESS = Volume of 0.01M EDTA solution in ml ------------------------------------------------- × 1000 ppm of CaCO3. Volume of sample water in ml

  32. 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 HCl 1000 ml of 0.05N HCL contain (36.5 x 0.05) or 1.825 gm HCl So, 100 ml of 0.05N HCl contain 0.1825 gm HCl Let, the concentration of diluted HCl is 35%, then 35 gm HCl present in 100 ml of diluted HCl & 0.1825 gm HCl present in {(100 x 0.1825)/35} or 0.528 ml diluted HCl

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

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

  35. Determination of permanent hardness of supply water (by di-sodium salt of EDTA) 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-EDTA In 0.01M solution of 1000ml contain 3.72 gm Na2-EDTA In 0.01M solution of 100ml contain 0.372 gm Na2-EDTA

  36. 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.

  37. Calculation: Total hardness = Volume of 0.01M EDTA solution in ml ---------------------- --------------------------× 1000 ppm of CaCO3. Volume of sample water in ml

  38. Methods for water softening 1. Lime-soda process 2. Base exchange process 3. Demineralization process 4. Sequestering agent

  39. 1. Lime-Soda process 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 H2O Mg(HCO3)2 + Ca(OH)2  MgCO3 + CaCO3 + 2 H2O MgCO3 + Ca(OH)2  Mg(OH)2 + CaCO3 For permanent hardness – CaSO4 + Na2CO3  CaCO3 + Na2SO4 MgCl2 + Ca(OH)2  CaCl2 + Mg(OH)2 CaCl2 form is removed by – CaCl2 + Na2CO3  2 NaCl + CaCO3

  40. The Plant: In lime soda softening plant main parts are- 1. Reagent tank (Soda lime + Coagulants) 2. Reaction tank 3. Filter 4. Soft water storage tank.

  41. Lime-Soda process PROCESS The 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 RESULT By 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.

  42. 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. Basic Principle For temporary hardness – 2Na-Permutit + Ca(HCO3)2  Ca-Permutit↓ + 2NaHCO3 For permanent hardness – 2Na-Permutit + CaSO4  Ca-Permutit↓ + Na2SO4 2Na-Permutit + MgSO4  Mg-Permutit↓ + Na2SO4 2Na-Permutit + MgCl2  Mg-Permutit↓ + 2NaCl

  43. Permutit process (Base/ Ion exchange method) Regeneration of Zeolites For 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.

  44. Permutit process (Base/ Ion exchange method) PROCESS The Zeolites are taken in the vessel as shown in figure with other required substances. When the hare ward is passed through the inlet, 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.

  45. 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 exchanger. – Cation exchanger and Anion

  46. Cation exchange: 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 + 2HCl H2R + CaSO4  CaR + H2SO4  General reaction – 2(Polymer – SO3¯H+) (s) + Ca²+ (aq) ↔ (Polymer – SO3¯)2Ca²+ (s) + 2H+ (aq)

  47. Anion 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

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