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Lecture 10 environment friendly dyeing of cotton
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Lecture 10 environment friendly dyeing of cotton

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Lecture 10 environment friendly dyeing of cotton Lecture 10 environment friendly dyeing of cotton Presentation Transcript

  • ENVIRONMENT FRIENDLY DYEING OF COTTON R.B.CHAVAN Department of Textile Technology Indian Institute of Technology Hauz-khas, New Delhi 110016 E-mail: rbchavan@hotmail.com
  • PRESENT CONCEPT
      • POLLUTERS MUST PAY
        • CRADLE TO GRAVE
        • WOMB TO TOMB
        • NOT ONLY FINAL PRODUCT BE ECO FRIENDLY
        • RAW MATERIALS, PRODUCTION PROCESSES, PACKAGING, ECO FRENDLY EVEN AFTER DIPOSAL
        • MEET EMS 14000 AND SAS 1800 STANDARDS
        • ECO FRIENDLY PRODUCTS INDENTIFIED BY ECO LABLES
    • GREEN MINDED CONSUMER PREFER ECO PRODUCTS EVEN AT HIGH COST
  • ENVIRONMENT FRIENDLY CHEMICAL PROCESSING Input / output analysis of Textile chemical Processes Textile Auxiliaries Dyes Base chemicals (e.g. acid, Alkali, sodium chloride) Textile Energy Natural Fibres; 10-20 MJ/kg Chemical Fibres: 5-50 MJ/kg Water 60-360 l/kg textile Polluted Air Water Effluent Waste Sewage sludge: 60-70 g/kg textile Wet Processing (pre-treatment, dyeing, printing, finishing.)
  • ENVIRONMENT FRIENDLY DYEING
    • DYE CLASSES FOR CELLULOSIC
    • REACTIVE
    • VAT
    • DIRECT
    • AZOIC
    • SULPHUR
    • EFFLUENT
    • RESIDUAL DYE
    • SALT
    • ALKALI
    • REDUCING AGENT
    • OXIDIZING AGENT
    • DETERGENT
  • REACTIVE DYES
    • ENVIRONMENTAL PROBLEM
    • COLOUR IN EFFLUENT
    • SALT IN EFFLUENT
  • Typical dye fixation on different fibres
  • ALTERNATIVE METHODS FOR LOW COLOUR IN EFFLUENT
    • DYEING AT LOW LIQUOR RATIO
    • CAREFUL FOLLOW UP OF DYESTUFF MANUFACTURERS RECOMMENDATION FOR DYEING CONDITIONS FOR OPTIMUM DYE FIXATION
    • RIGHT FIRST TIME APPROACH TO AVOID
    • SHADING ADDITIONS
    • STRIPPING AND REDYEING OF OFF SHADES
    • USE OF HIGH FIXATION BIFUNCTIONAL REACTIVE DYES
  • BIFUNCTIONAL REACTIVE DYES
    • HOMO BIFUNCTIONAL REACTIVE DYES
    • ORIGINALLY PROMOTED BY ICI (NOW ZENECA) AS PROCION SUPRA DYES FOR PRINTING AND THEN PROCION H-E DYES FOR DYEING (HOMO BIFUNCTIONAL MONO CHLORO TRIAZYNYL)
    • HETRO BICUNTIONAL REACTIVE DYES
    • CHARACTERIZED BY THE PRESENCE OF TWO REACTIVE GROUPS OF DIFFERENT REACTIVITIES
    • CAN BE APPLIED OVER A TEMPERATURE RANGE OF 60-80 0 c
    • BETTER SHADE REPRODUCIBILITY EVEN WITH TEMPERATURE VARIATION
    • AVAILABLE FROM MAJOR DYESTUFF MANUFACTURERES
  • BIFUNCTIONAL REACTIVE DYES
  • LOW SALT REACTIVE DYES
    • SALT REQUIREMENT
    • CONVENTIONAL REACTIVE DYES 60-80 g/l
    • LOW SALT REACTIVE DYES 20 g/l
    • FEATURES ( CIBACRON LS)
    • BIFUNCTIONAL REACTIVE DYES
    • TWO CHROMOPHORES CONTRIBUTE HIGH AFFINITY AND HIGH COLOUR STRENGTH
    • HIGH FIXATION
    • STABLE DYE-FIBRE BOND
  • EFFECT OF SALT ON ENVIRONMENT
    • EFFLUENT TREATMENT REMOVES ONLY SMALL QUANTITY OF SALT
    • MAJOR QUANTITY OF SALT REMAINS IN WATER
    • RIVERS AND LAKES GET POLLUTED WITH EFFLUENT CONTAINING HIGH SALT CONCENTRATION
    • FRESH WATER ORGANISMS CAN SUFFER TOXIC EFFECTS
    • IN REGIONS WITH SCARCE FRESH WATER RESOURCES SUCH WASTE WATER HAS TO BE USED FOR LAND IRRIGATION
    • REDUCTION IN LAND FERTILITY AND ULTIMATELY HAVE TO BE ABONDONED
  • APPROACHES TO SOLVE PROBLEMS OF SALT LOAD
    • DYEING AT LOWEST POSSIBLE LIQUOR RATIO
    • USING DYE CLASSES OTHER THAN REACTIVE SUCH AS VAT REQUIRING LOW SALT CONCENTRATION FOR DYEING
    • USING REACTIVE DYES GIVING HIGH EXHAUSTION AND FIXATION AT LOW SALT CONCENTRATION
  • GENERAL STRUCTURE OF LOW SALT REACTIVE DYES CHROMOPH-ORE CHROMOPHORE BRID-GE REACT-IVE GROUP REACT-IVE GROUP
  • ADVANTAGES OF HIGH DYE FIXATION Conventional dyes 60 % fixation Cibacron LS (bireactive) 80 % fixation 200 gm into the waste water 800 gm on the fibre 1 kg dye + 33% % - 50% % 1 kg dye 600 gm on the fibre 400 gm into the waste water
  • ECOLOGICAL BENEFITS OF LOW SALT REACTIVE DYES
    • Property Benefit
    • High fixation rate Low dye concentration in effluent
    • Low electrolyte concentration Low salt effluent and cost/time saving
    • Good wash off Less water and energy Low BOD values
    • Halogen-free chromophores No AOX in effluent
    • Free from carcinogenic amines No health risk to dyes No risk of ban
    • High repeatability of dyeing Less shading and stripping
  • ECO FRIENDLY REDUCING AGENTS FOR VAT DYES
    • SODIUM HYDROSULPHITE IS UNIVERSALLY USED
    • DURING DYEING CONVERSION TO SULPHITE AND SULPHATE
    • SULPHITE IS TOXIC TO FISH AND BACTERIA
    • SULPHATE IS NON-TOXIC TO FISH AND BACTERIA IT MAY CAUSE CORROSION OF CONCRETE PIPES
  • ALTERNATE REDUCING SYSTEMS
    • HYDROXY ACETONE
    • CAN TOTALLY REPLACE HYDROSULPHITE
    • BIO-COMPATIBLE
    • GIVE 20% HIGHER COLOUR YIELD WITH INDIGO
    • EXPENSIVE
    • NOT READILY AVAILABLE
    • YET TO USE ON COMMERCIAL SCALE
  • ELECTROCHEMICAL REDUCTION
    • DIRECT REDUCTION OF DYE BY CONTACT BETWEEN DYE DISPERSION AND ELECTRODE
    • ADDITION OF SMALL QUANTITY OF HYDROSULPHITE IS ESSENTIAL TO MAINTAIN DYE IN REDUCED STATE
    • METHOD PRODUCES LIGHTER SHAED COMPARED TO HYDRO SULPHITE
  • IRON COMPLEXES
    • USE OF Fe(OH) 2 AS REDUCING AGENT
    • COPPERAS METHOD KNOWN FOR LONG FOR DYEING OF INDIGO
    • USE OF FeSO4 AND Ca(OH)2
    • Fe(OH)2 HAS VERY LOW WATER SOLUBILITY
    • PRECIPITATES IN DYEBATHN NO REPRODUCIBLE RESULTS
    • NOT SUITABLE FOR VAT DYES OTHER THAN INDIGO
    • USE OF GLUCONIC ACID IS SUGGESTED IN GERMAN LITERATURE FOR ENHANCING SOLUBILITY OF Fe(OH)2
    • GLUCONIC ACID IS EXPENSIVE
  • STUDY AT IIT DELHI R.B.chavan, J.N.chakraborty
    • USE OF CITRIC ACID, TARTARIC ACID AND TRIETHANOL AMINE TO ENHANCE SOLUBILITY OF Fe(OH)2
    • REDUCTION POTENTIAL HIGHER THAN HYDRO SYLPHITE
    • POSSIBLE TO REDUCE VAT DYES AT ROOM TEMPERATURE
    • DYEING AT ROOM TEMPERATURE
    • COLOUR YIELD AND FASTNESS PROPERTIES COMPARABLE TO HYDROSULPHITE
    • TOTAL REPLACEMENT OF HYDROSULPHITE
    • ENVIRONMENT FRIENDLY AND ENERGY SAVING SYSTEM
  • SULPHUR DYES
    • Na2S IS COMMONLY USED REDUCING AGENT
    • NO ODOUR NUISANCE ABOVE pH 9
    • LIBERATION OF H2S UNDER ACID CONDITIONS
    • FOUL SMELL OF ROTTEN EGGS
    • TOXIC WHEN INHALED
    • ODOUR THRESHOLD LIMIT 10 ppm
    • TOXIC TO FISH
  • OXIDATION
    • USE OF HALOGENATED COMPOUNDS LIKE BROMATE, IODATE PRODUCE ORGANIC HALOGEN COMPOUNDS RESPONSIBLE FOR ADSORBABLE ORGANIC HALOGEN (AOX)
    • AOX IS TOXIC TO AQUATIC LIFE
    • DICHROMATE IS MORE RISKY, HEALTH HAZARDS
    • SAFE OXIDIZING AGENT IS H 2 O 2
  • Na 2 S REPLACEMENT
    • β – MERCAPTOETHANOL MARKETED BY BASF AS MOLESCAL SF
    • LOWER COLOUR YIELD COMPARED TO Na2S
    • INCOMPLETE DISSOLUTION OF SOME SULPHUR DYES
    • SUITABLE FOR LIMITED RANGE OF SULPHUR DYES
    • COSTLY
    • GLUCOSE
    • CAN BE USED AS REDUCING AGENT FOR SULPHUR DYES
    • GIVES REDUCTION POTENTIAL SUITABLE FOR REDUCTION OF SULPHUR DYES UNDER ALKALINE CONDITIONS ABOVE 60 0 c
    • CENTURY MILL (MUMBAI) HAS SUCCESSFULLY REPLACED Na2S WITH GLUCOSE ON INDUSTRIAL SCALE
    • HYDROL, VISCOUS LIQUID AVAILABLE COMMERCIALLY AT LOW COST
  • CONCLUSION
    • USE OF BIFUNCTIONAL REACTIVE DYES FOR LOW COLOUR IN EFFLUENT
    • USE OF LOW SALT REACTIVE DYES FOR REDUCTION OF SALT IN EFFLUENT
    • REPLACEMENT OF Na2S WITH GLUCOSE IN SULPHUR DYEING
    • REPLACEMENT OF HYDROSULPHITE IN VAT DYEING BY
    • IRON COMPLEXES
    • ELECTROCHEMCAL REDUCTION METHOD