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Hardness of water

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For engineering First Year STudents

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Hardness of water

  1. 1. Hardness of water
  2. 2. Applied Chemistry LEARNING TARGETS  Basics of water  Sources of water  Impurities in water  Effect of impurities  Alkalinity of water  Hardness of water
  3. 3. Applied Chemistry  Troubleshooting due to hard water Boiler corrosion, causes and prevention Caustic imbrittleness , causes and prevention  Softening of water Soda lime process Zeolite Ion exchanger  Water treatment for municipal water supply
  4. 4. Applied Chemistry Basics of water “A clear transparent liquid, perfectly neutral in reaction and devoid of taste or smell” In the pure state it is composed of oxygen and hydrogen in proportion of 1:2 by volume
  5. 5. Applied Chemistry Concept of pure water “Water that is free from objectionable color, odor, taste & turbidity is called pure water” “Pure water which contains adequate amount of dissolved oxygen but no microorganisms and other organic pollutants and is free of microbial and chemical toxins is called wholesome water” Pure water Wholesome water
  6. 6. Applied Chemistry Key H2O Characteristics • Water is clear, transparent, tasteless liquid at ordinary temp. in the pure state. • It is prime constituent of all living organisms. • Water moves easily from one physical state to another, and from one place to another. • Its specific gravity is 1 • It is bad conductor of heat and electricity • It expands on heating and at 1000c it gives invisible vapors at 1 atm. pressure • On cooling it contracts till 40c • It has maximum density at 40c • Further lowering of temperature, it further contracts and solidify at 00c • Water slowly absorbs and releases large quantities of energy. • Water is a superior solvent and solubalise many solute at low or elevated temp • It liberates heat when H2SO4 or HCl is added to it. • NH4Cl, NH4SCN, NaNO2 is added to it.
  7. 7. Applied Chemistry
  8. 8. Applied Chemistry How much water is available ?
  9. 9. Applied Chemistry •It is a universal solvent. •It is an efficient transport medium (nutrients) •Facilitates thermoregulation in body. •Helps in maintenance of blood and plasma volume –cellular osmotic pressure. •Assist in secretary and excretory functions of body–constituent of enzyme & hormonal secretions. •Valuable medium for administration of therapeutics. •Helps in propagating useful aquatic flora and fauna. •Essential for irrigation, power generation & domestic purpose. Functions of Water
  10. 10. Applied Chemistry • Industrial growth & development has increased the sewage production. • Increased flow of sewage and organic matter has increased the BOD from 1 mg/liter (for neutral waters) to 300-500 mg/liter (polluted water). • Micro-organisms present in farm and domestic effluents are added to fresh water sources (rivers & lakes). • Dissolved salts can make water hard and unpalatable • Industrial wastes rich in intermediate products & heavy metals, etc are added to river streams. Need for water purification
  11. 11. Applied Chemistry •To remove color, objectionable odor and taste. •To remove dissolved gases and suspended solids. •To remove suspended and dissolved organic solids. •To remove pathogenic bacteria. •To make water safe for industrial, drinking and domestic purpose. Objectives of Water Purification
  12. 12. Applied Chemistry Sources Rain water Surface water Sea Water Lakes and ponds Stream and riverGround water Sources of water
  13. 13. Applied Chemistry
  14. 14. 1. Suspended impurities Clay, sand, Vegetable matter etc. 2. Dissolved impurities Bicarbonate, Chloride, Sulfate of Ca and Mg Dissolved O2, CO2, H2S 3. Colloidal impurities Fe(OH)3, Al(OH)3 4. Biological impurities Impurities in water
  15. 15. Applied Chemistry Effect of impurities 1. Imparts color 2 Impart odor 3. Impart Taste 4. Impart Turbidity 5. Impart Alkalinity 6. Impart Hardness Minerals
  16. 16. It is mainly due to 1. Only hydroxide (OH-) 2. Only carbonate (CO3 - -) 3. Only Bicarbonate (HCO3 - ) 4. Both hydroxide (OH-)and carbonate (CO3 - -) 5. Both carbonate (CO3 - -)and bicarbonate (HCO3 - ) 6. But not due to hydroxide (OH-) and (HCO3 - ) Alkalinity of water OH- + HCO3 - H2O + CO2
  17. 17. Methods of determination of alkalinity of water Water Sample Phenolphthaline Pink color Phenolphthalein end point (colorless) (P) Methyl orange indicator Yellow Methyl orange end point (red color) (M)
  18. 18. 1. Temporary hardness  It is due to bicarbonate of calcium and magnesium  It is removed by boiling Boil soluble In soluble Ca (HCO3)2 CaCO3 + H2O + CO2 Mg (HCO3)2 MgCO3 + H2O + CO2 soluble In soluble Boil Hardness of water
  19. 19.  It is due to chloride and sulfate of calcium and magnesium  It is not removed by boiling 2. Permanent hardness
  20. 20. Methods of determination of hardness of water 1. Soap titration method. When soap is added to water, it combines with hardness producing impurities to form insoluble compounds and do not produce lather. Further addition of soap solution produces lather 2 C17H35COONa + CaSO4 (C17H35COO)2 Ca + Na2SO4 2 C17H35COONa + CaCl2 (C17H35COO)2 Ca + NaCl 2 C17H35COONa + MgSO4 (C17H35COO)2 Mg + Na2SO4 2 C17H35COONa + MgCl2 (C17H35COO)2 Mg + NaCl 2 C17H35COONa + Ca(HCO3)2 (C17H35COO)2 Ca + NaHCO3 2 C17H35COONa + Mg(HCO3)2 (C17H35COO)2 Mg + NaHCO3
  21. 21. 2. EDTA method Structure of EDTA CH2CH2 NN CH2COOH CH2COOH HOOCCH2 HOOCCH2 CH2CH2 NN OOCH2C CH2COOHCH2COOH CH2COO M Structure of Metal EDTA complex
  22. 22. Applied Chemistry Units of Hardness Hardness of water is express in CaCO3 equivalent For conversion of any salt into its CaCo3 Equivalent it is multiplied by a multiplication number CaCO3 equivalent of salt = Wt of salt x M. W. of CaCO3 / M. W. salt

Notas

  • J D College of Engineering Nagpur
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