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11st SEM Applied Chemistry SRM University1st SEM Applied Chemistry
2Technology Of Water Water: Water is a chemical substance with the chemical formula H2O.Existance on Earth1. Solid state-ice,2. Gaseous state (water vapor or steam)3. LiquidWater is not only universal solvent but also an essential material for engineering applications.Prime factor in developmentWater on Earth moves continually through a cycle of evaporation or transpiration (evapotranspiration),
4Evapotranspiration (ET) is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere.Evaporation :-The movement of water to the air from sources such as the soil, canopy interception, and water bodies.Transpiration :-The movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves.An element (such as a tree) that contributes to evapotranspiration can be called an evapotranspirator.
5Sources of Water The source of water are listed under two categories 1. Surface Water2. Underground WaterSurface Waters:1. Rain Water2. River Water3. Lake Water4. Sea waterB. Underground Water:1. Spring2. Well water
7Types Of Impurities 1. Dissolved Impurities: a) Inorganic salts e Types Of Impurities 1. Dissolved Impurities: a) Inorganic salts e.g sulphates and chlorides of calcium, Magnesium, Iron b) gases like carbon dioxide, nitrogen , oxygen, hydrogen sulphides c) organic salts 2. Suspended Impurities: a) Clay b) mud c) Vegetable and animal matters
83. Colloidal Impurities: a) fine size like silica and alumina, organic wastes etc.These are soluble materials, other than gasescannot be removed by conventional filtersreferred as TDS which stands for total dissolved solids.4. Bacterial Impurities:a) Bacteria, Germs, Pathogens, Microbes, Viruses, Parasitesinclude- algae, beneficial bacteria that decompose wastes- harmful bacteria such as those that cause cholera.
9Effects of Impurities: a) colour of surface water- dissolved organic mattersb) Taste and Odour- formation of compoundsc) Turbidity- suspended Impuritiesd) Pathogenicity- micro organismsHardness of WaterCharacteristics of water which prevent the Leather Formation.due to presence of:- salts like bicarbonates, sulphates,chlorides of mg and other metalsUnits of Hardness:1) ppm ) mg/l ) ̊Cl ) ̊FrRelation - 1ppm = 1mg/l = ̊Cl = 0.1 ̊Fr
10Hardness Table Water Classification Hardness, mg/L Hardness. Grains/GalSodium Added mg/LSoft0 to 490 to 2.90 to 22.5Medium Hard50 to 1492.9 to 8.723 to 68.5Hard150 to 2498.7 to 14.669 to 115Very Hard250 to 29914.6 to 173115 to 138Extremely Hard300 and up17.5 and up138 and upmg/L = milligrams/Liter
11Types of Hardness1) Temporary:- 0r Carbonate HardnessWater that contains bicarbonate of calcium and magnesium or of bothremoved by boilingCa(HCO3)2 → CaCO3 ↓ + CO2 ↑+ H2OMg(HCO3)2 → Mg (OH) 2 ↓ + 2CO2 ↑Permanent :- or Non- Carbonate HardnessContains chlorides or sulphates of calcium or magnesium or of bothCan not be removed by boilingCaCl2 → Ca+2 + 2Cl-1MgSO4 → Mg+2 + SO4-2
12Disadvantages of Hard Water (A) Domestic Uses:Washing Bathing Drinking CookingC17 H35 COO Na + H2O→ C17 H35 COOH + NAOHC17 H35 COOH + C17 H35 COO Na → LatherC17 H35 COO Na + CaSO4 → (C17 H35 COO) 2 Ca ↓ + Na2SO2(in water) (White Scum)(B) Industrial Uses:1. Boiler Feed: should not contain nitrates- scale and sludges2. Paper Mill: should not contain iron and lime- destroy resin of soap3. Sugar industries: Sulphates and Alkaline carbonates- Deliquescent4. Dyeing Industries: should not contain iron and hardness5. Laundries: should be soft
13Estimation Of Hardness 1. EDTA Method O.Herner’s MethodEDTA Method:Ethylene Diamine Tetra Acetic Acid-OOOCH CH2COO-NCH2.CH2NEstimation is by titration method at pH 10Using Indicator Eriochrome Black-TMethod:Take 50 ml water in coinical flaskAdd buffer and few drops of EBT-TTitrate against EDTARed colour change to steel blue/violet
14For Temporary Hardness: O.Herner’s Method (0r) Alkali Titration MethodBicarbonates of Ca and Mg makes water alkaline and can react with HClCa(HCO3)2 + 2HCl → CaCl2 + 2CO2 ↑+ 2H2OMg(HCO3)2 + 2HCl → MgCl2 + 2CO2 ↑+ 2H2OCa(HCO3)2 and Mg(HCO3)2 decomposes into insoluble carbonates on boiling the water.For Temporary Hardness:50ml sample water in conical flask2-3 drops of methyl orange indicatorTitrated against N/50 HClChange colour from yellow to orangeTake 100 ml of same sample of waterBoil until 1/5th volumeMake them again 100 ml Distilled waterTake 50ml and perform again the above steps
15For Permanent Hardness Caused by Chlorides and Sulphates of Calcium and MagnesiumCan be determined by using Na2CO3 and HCl.CaCl2+Na2CO3→CaCO3 ↓+ 2NaClCaSO4+Na2CO3→CaCO3 ↓ + 2NaSO4Method:50 ml hard water + 50 ml Na2CO3 solutionBoiled and Evaporated to dryness.Chlorides of Ca and Mg ppt. as carbonates of Ca and Mg.Extract residue with distilled waterAdd few drops of methyl orange as indicatorTitrate against N/50 HClEnd point changes colour from yellow to orange.
16Determination of Alkalinity in water It is due to 1) OH- and CO3-2 2) HCO3-Titrate against phenolphthalein and methyl orangeMethod100 ml sample water in conical flaskAdd 2-3 drops of phenolphthalein indicatorTitrate against N/50 H2SO4Continue till pink colour disappearTo the same solution add 2-3 drops of methyl orangeTitrate till yellow colour changes to redReaction Involved:OH-+H → H2O (using phenolphthalein)CO3-2+ H+→ HCO (using phenolphthalein)HCO3-+H+ → H2O+ CO2 (using methyl orange)
17Scale and SludgeTroubles met in boiler which are used in steam production.Scale:When water is evaporated in boilers to produce steam continuouslythe concentration of the slats present in the water increases progresselyAs the concentration reaches a saturation point the salts are thrownover the inner surface of the boiler.Sludge:During boiling salts form precipitate of loose slimy form.Magnesium ChlorideDecomposes to form hydroxide and hydrochloric acids. The former will produce hard scale and the later lowers the pH.MgCl2 + 2H2O 2HCl + Mg(OH)2Magnesium SulphateForms a hard scale on the heating surfaces
18Calcium Sulphate Forms a hard scale on the heating surfaces Calcium Bi-carbonate Decomposes at a low temperature when CO2 is liberated. Remaining Calcium carbonate deposits on the heating surface as a soft scale. Ca(HCO3)2 CaCO3 + CO2 + H2O
19Disadvantages of Scale Formation 1. Wastage of fuel Decreases in Efficiency3. Lowering of boiler safety Danger of Explosion5. CorrosionRemoval of ScalesBy scrapping Giving thermal shocks3. Dissolving by using chemicals e.g CaCO3 by 5-10% HCl4. Adding complexing agents e.g CaSO4 by EDTA5. Blow down ProcessDisadvantages of Sludge FormationChocking of pipesLow supply of heatWastage of fuelGet entrapped in scales
20Prevention of Sludge Formation Blow down Process: Withdrawing portion of sludge containing water and replacing with fresh waterSoftening of waterMethod of Preventing Scale FormationExternal Treatment:Treatment of water before entering into boiler- Removal of Ca, Mg and Silica2. Internal Treatment:Addition of chemicals directly to water in boiler.Scale forming substances produces loose precipitateBlow down processAdding complexing agents: to form soluble complex
21Caustic embrittlement : It is the phenomenon in which the material ofa boiler becomes brittle due to the accumulation of caustic substances.Sodium carbonate is used in softening of water by lime soda process, due to this some sodium carbonate maybe left behind in the water.Na2CO3 + H2O → 2NaOH + CO2As Conc. of NaOH increases, water flows into minute hair cracks.Water get evaporated and NaOH increases further and react with iron of boiler, hence cause Embrittlement.Prevention:Addition of sodium sulphate or sodium phosphate. Which will block hair-cracks.Addition of tannin and lignin- blocks the cracks.Excess of Na2SO4 is avoided else it will form CaSO4
22Priming:- Carry over of varying amounts of water in the steam e.g. Priming and FoamingPriming:- Carry over of varying amounts of water in the steam e.g.(Foam, mist)Leads to deposits of salt crystalsLowers the energy efficiencyCauses:-Presence of suspended impurities and dissolved saltsHigh steam velocity and sudden boilingHigh water levelsFaulty boiler designPreventions:Good boiler designAvoid rapid changes in temp.Maintaining low water levelFitting mechanical steam purifierNormal BubbleCarry Over
23Foaming: Formation of small bubbles and forth on the surface of water Caused by high conc. of any solids in waterCauses:Difference b/w conc. of solute and suspended matters.Surface tension lowering substancesOil and greasePrevention:Adding antifoaming agents e.g. castor oilRemoving oily particles using silicic acid and sodium alluminate.Boiler Corrosion: Decay of material by chemically or electrochemicallyPresence of dissolved gases e.g. O2 , CO2Caustic EmbrittlementAcid formation due to HydrolysisPresence of free acids.
24Internal Treatment Method Treatment Methods of WaterA. Internal TreatmentB. External TreatmentInternal Treatment MethodPhosphate Conditioning:- Small amount of phosphate ions are added to precipitate Ca ions.- Chosen depending on the pH conditions of boiler.2. Colloidal Conditioning:Using kerosine, tannin, starch etcGet coated over the scale forming particlesRemoved by Blow down Process3. Carbonate conditioning:Na2CO3 is added to precipitate Ca salts as CaCO3Used in low pressure boilers
25Calgon Conditioning:Scale forming salts are converted into soluble complexes.E.g. Sodium Hexameta Phosphate (Na2PO3)6 is added…reacts with Ca and forms Calcium Hexameta Phosphate (Ca2PO3)6Prevents Scale formationRadioactive conditioning:Adding radioactive tabletsEmits radiation energy which prevents Scale formationElectrical Conditioning:Mercury bulbs placed in boilerEmits electrical discharge
26External Treatment Method (or) Water softening Method Removal of hardness causing substances from waterMethods:Zeolite processIon Exchange ProcessMixed Bed deionizationZeolite (or Permutit) Process: are Hydrated sodium alumino SilicateNa2O. Al2O3 X SiO2 Y H 2O (X= 2-10, Y= 2-6 )Natural Zeolites:Natrolite Na2O. Al2O3 4SiO2 .2H 2OLaumontite - CaO. Al2O3 4SiO2 .4H 2OHarmotome - (BaO.K2O). Al2O3 5SiO2 .5H 2O- Capable of exchanging its Na ions.
27A. Natural Zeolite:-Derived from green sand by washing, Heating, treating with NaOH.Non porous in nature.B. Synthetic Zeolite: -Prepared from solution of Sodium Silicate and AlOHHigher exchange capacity and porous in Nature.Process:
28Consist of Steel TankHaving Thick Layer of ZeoliteWhen water pass through it hardness causing ions (Ca, Mg) are retained by Zeolite.Chemical Reaction:Ca(HCO3) 2 + Na2 Ze → CaZe + 2 NaHCO3CaSO4 + Na2Ze → CaZe + Na2SO4MgCl 2 + Na2Ze → MgZe + 2NaClMg (NO3)2 + Na2Ze → MgZe + 2NaNO3Exchange of Na ions continues until Na ions are exhaustedRegeneration:CaZe + 2NaCl → Na2Ze + CaCl 2MgZe + 2NaCl → Na2Ze + MgCl 2CaCl 2 and MgCl 2 led to drain and Na2Ze can be reused.
29AdvantagesHardness can be completely removedProcess can be made automaticallyEasy operation. No experts requiredLess time and sludgeSmall area requiresDisadvantagesOnly Ca+ and Mg+ ions can be removedLarge amount of Na ions present in treated water.Leaves other acids which causes corrosionFe 2+ and Mn 2+ containing water can not be treated because Fe and Mn Zeolite can not be regeneratedWater should be free from suspended impurities to prevent clogging on Zeolite beds.Treated water contains more dissolved solids.
30B. Ion Exchange (or) Demineralization (or) Deionization Process. mineral ions are removedphysical process which uses specially-manufactured ion exchange resins which bind to and filter out the mineral salts from water.
31Advantage:Produces soft waterCan treat highly acidic or alkaline waterRegeneration of ion resins are possibleMaintenance cost is lowDisadvantage:Cost of equipment is highHighly turbid water can not be treatedExpensive chemicals are required.
323. Mixed Bed Deionization This equipment consist of single column which contain mixture of cation and anion exchangers.When water pass through bed, it comes in contact several times with both exchangersResultant water contain lesser amount of salt.Regeneration: by back washa) anions with dil. NaOHb) cations with dil. H2SO4Advantages:More convenient and more effectiveDisadvantages:Regeneration cost is moreEquipment cost is high
33DesalinationProcesses that remove some amount of salt and other minerals fromWater.Brackish Water: contain 3.5 % salts & salty taste. Unfit for drinkingSeparation of salts from water by evaporation followed by condensation.Freezing method can also be employedCommonly used methods:ElectrodialysisReverse Osmosis
34A. Electrodialysis:Method of separation of ions from salt water by passing electric current.Semi permeable membranes are placedConsist of three compartments containing1. Sea Water 2. Pair of electrodes Semi permeable membrane
35As current applied Na ions moves towards cathode and Cl moves towards anode As result brine concentration decreases in the middle compartment.Pure water is removed from the central compartment.Conc. Brines are replaced by fresh brine water.Much more effective separation Ion selective membranes are used
36Reverse Osmosis (or) Super Filtration (or) Hyper Filtration Movement of solvent molecule from concentrated side to diluted side.If only pressure higher than that of osmotic pressureMembranes:Cellulose Acetate, Polymide,PolymethylmethaacrylateThickness:to µmAdvantages:Removes both ionic and non ionic and colloidal mattersMaintenance cost is lowMembrane replacement can be done with in few minutes.
37Domestic Treatment of Water Removal of Suspended ImpuritiesRemoval of Micro organismsScreening:Floating matters are removed by passing through screens.2. Sedimentation:Big tanks are usedLeft undisturbedWater settle down due to gravity.Supernatent water is drawn with the help of pumpTakes 2-6 hours3. Filtration:Sand Filters are used.
384. Sedimentation with Coagulation: Addition of Chemicals (Coagulants) to water. E.g. Alum (Potash Alum or Ferric Alum), Sodium Aluminate (NaAlO2) ,Ferrous Sulphate (FeSO4)On addition they form an insoluble gelatinous, flocculent precipitate which absorbs very fine particles and form bigger flocs.Due to this tiny particles which have no charge also come closers.
39B. Removal of Micro Organisms BoilingAdding Bleaching Powder:1 kg for 1000 KLMixed and Allowed to stand several hoursCaOCl2 + H2O → Ca (OH)2 + Cl2Cl2 + HO → HOCl (Hypochlorous Acid) + HClHOCl + Germs → Germs KilledHOCl → HCl+ [O] (Nascent Oxygen)[O] + Germs → Germs KilledDisadvantages:Excess addition give bad odour and taste.Introduces Ca into water and makes it hardDisintegrates on storing
403. By Chlorination:Chlorine produces Hypochlorous Acid.Hypochlorous acid is strong Germicide.Cl2 + HO → HOCl (Hypochlorous Acid) + HClHOCl + Germs → Germs KilledCl may be used in Gaseous or Concentrated Form.Filtered water with ppm Cl is sufficient.Lower pH is favourable (5-6.5)Advantages:Effective and EconomicalStable and does not deteriorate on storageNo impurities such as salts are introduced.Can be used at high as well as low temp.
41DisadvantagesExcess chlorination produces unpleasant taste. ( ppm only)More effective at low pH.Breakpoint Chlorination:The addition of chlorine in such amount that it Oxidizes the organic matter, reducing matters and free ammonia in raw water. And leaves free residual Cl which disinfect Water.AdvantagesOxidizes organic compounds, reducing substances and ammonia.Removes colour and taste.Kill germs.- Excess of Declorination can be done byFiltering through bed of molecular carbonAddition of SO2 and Na2SO3SO2 + Cl2 + 2H 2O → H 2SO4+ 2HClNa2SO3 + Cl2 + H 2O → Na2SO4 + 2HCl
424. By chloramine:- Using 2 : 3 ratio of Cl3 and NH3ClNH2+ H2O → HOCl + NH3HOCl + Germs → Germs Killed5. By Ozonization:Ozone and raw water are allowed to come in contact with each other10 – 15 min. in 2-8 ppm3O → 2O3 (Highly Unstable)O → O2 + [O][O] + Germs → Germs KilledAdvantage: 1. Leaves no residue. Because of unstability2. Removes odour, colour, Taste.Disadvantage: Very Expensive6. By Ultraviolet Radiation:- Using Electric mercury vapour lamp
43International Standards for water Water should be free from Depends on purposeStandards Set By:WHO- World Health OrganizationUSPHD- United States Health ServiceICMR- Indian Council of Medical ResearchWater should be free fromTurbidity, ColourTaste, OdourMicrobesToxicity (Organic and Inorganic Metals)