Lecture 10 environment friendly dyeing of cotton

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Lecture 10 environment friendly dyeing of cotton

  1. 1. 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
  2. 2. PRESENT CONCEPT <ul><ul><li>POLLUTERS MUST PAY </li></ul></ul><ul><ul><ul><li>CRADLE TO GRAVE </li></ul></ul></ul><ul><ul><ul><li>WOMB TO TOMB </li></ul></ul></ul><ul><ul><ul><li>NOT ONLY FINAL PRODUCT BE ECO FRIENDLY </li></ul></ul></ul><ul><ul><ul><li>RAW MATERIALS, PRODUCTION PROCESSES, PACKAGING, ECO FRENDLY EVEN AFTER DIPOSAL </li></ul></ul></ul><ul><ul><ul><li>MEET EMS 14000 AND SAS 1800 STANDARDS </li></ul></ul></ul><ul><ul><ul><li>ECO FRIENDLY PRODUCTS INDENTIFIED BY ECO LABLES </li></ul></ul></ul><ul><li>GREEN MINDED CONSUMER PREFER ECO PRODUCTS EVEN AT HIGH COST </li></ul>
  3. 3. 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.)
  4. 4. ENVIRONMENT FRIENDLY DYEING <ul><li>DYE CLASSES FOR CELLULOSIC </li></ul><ul><li>REACTIVE </li></ul><ul><li>VAT </li></ul><ul><li>DIRECT </li></ul><ul><li>AZOIC </li></ul><ul><li>SULPHUR </li></ul><ul><li>EFFLUENT </li></ul><ul><li>RESIDUAL DYE </li></ul><ul><li>SALT </li></ul><ul><li>ALKALI </li></ul><ul><li>REDUCING AGENT </li></ul><ul><li>OXIDIZING AGENT </li></ul><ul><li>DETERGENT </li></ul>
  5. 5. REACTIVE DYES <ul><li>ENVIRONMENTAL PROBLEM </li></ul><ul><li>COLOUR IN EFFLUENT </li></ul><ul><li>SALT IN EFFLUENT </li></ul>
  6. 6. Typical dye fixation on different fibres
  7. 7. ALTERNATIVE METHODS FOR LOW COLOUR IN EFFLUENT <ul><li>DYEING AT LOW LIQUOR RATIO </li></ul><ul><li>CAREFUL FOLLOW UP OF DYESTUFF MANUFACTURERS RECOMMENDATION FOR DYEING CONDITIONS FOR OPTIMUM DYE FIXATION </li></ul><ul><li>RIGHT FIRST TIME APPROACH TO AVOID </li></ul><ul><li>SHADING ADDITIONS </li></ul><ul><li>STRIPPING AND REDYEING OF OFF SHADES </li></ul><ul><li>USE OF HIGH FIXATION BIFUNCTIONAL REACTIVE DYES </li></ul>
  8. 8. BIFUNCTIONAL REACTIVE DYES <ul><li>HOMO BIFUNCTIONAL REACTIVE DYES </li></ul><ul><li>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) </li></ul><ul><li>HETRO BICUNTIONAL REACTIVE DYES </li></ul><ul><li>CHARACTERIZED BY THE PRESENCE OF TWO REACTIVE GROUPS OF DIFFERENT REACTIVITIES </li></ul><ul><li>CAN BE APPLIED OVER A TEMPERATURE RANGE OF 60-80 0 c </li></ul><ul><li>BETTER SHADE REPRODUCIBILITY EVEN WITH TEMPERATURE VARIATION </li></ul><ul><li>AVAILABLE FROM MAJOR DYESTUFF MANUFACTURERES </li></ul>
  9. 9. BIFUNCTIONAL REACTIVE DYES
  10. 10. LOW SALT REACTIVE DYES <ul><li>SALT REQUIREMENT </li></ul><ul><li>CONVENTIONAL REACTIVE DYES 60-80 g/l </li></ul><ul><li>LOW SALT REACTIVE DYES 20 g/l </li></ul><ul><li>FEATURES ( CIBACRON LS) </li></ul><ul><li>BIFUNCTIONAL REACTIVE DYES </li></ul><ul><li>TWO CHROMOPHORES CONTRIBUTE HIGH AFFINITY AND HIGH COLOUR STRENGTH </li></ul><ul><li>HIGH FIXATION </li></ul><ul><li>STABLE DYE-FIBRE BOND </li></ul><ul><li> </li></ul>
  11. 11. EFFECT OF SALT ON ENVIRONMENT <ul><li>EFFLUENT TREATMENT REMOVES ONLY SMALL QUANTITY OF SALT </li></ul><ul><li>MAJOR QUANTITY OF SALT REMAINS IN WATER </li></ul><ul><li>RIVERS AND LAKES GET POLLUTED WITH EFFLUENT CONTAINING HIGH SALT CONCENTRATION </li></ul><ul><li>FRESH WATER ORGANISMS CAN SUFFER TOXIC EFFECTS </li></ul><ul><li>IN REGIONS WITH SCARCE FRESH WATER RESOURCES SUCH WASTE WATER HAS TO BE USED FOR LAND IRRIGATION </li></ul><ul><li>REDUCTION IN LAND FERTILITY AND ULTIMATELY HAVE TO BE ABONDONED </li></ul>
  12. 12. APPROACHES TO SOLVE PROBLEMS OF SALT LOAD <ul><li>DYEING AT LOWEST POSSIBLE LIQUOR RATIO </li></ul><ul><li>USING DYE CLASSES OTHER THAN REACTIVE SUCH AS VAT REQUIRING LOW SALT CONCENTRATION FOR DYEING </li></ul><ul><li>USING REACTIVE DYES GIVING HIGH EXHAUSTION AND FIXATION AT LOW SALT CONCENTRATION </li></ul>
  13. 13. GENERAL STRUCTURE OF LOW SALT REACTIVE DYES CHROMOPH-ORE CHROMOPHORE BRID-GE REACT-IVE GROUP REACT-IVE GROUP
  14. 14. 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
  15. 15. ECOLOGICAL BENEFITS OF LOW SALT REACTIVE DYES <ul><li>Property Benefit </li></ul><ul><li>High fixation rate Low dye concentration in effluent </li></ul><ul><li>Low electrolyte concentration Low salt effluent and cost/time saving </li></ul><ul><li>Good wash off Less water and energy Low BOD values </li></ul><ul><li>Halogen-free chromophores No AOX in effluent </li></ul><ul><li>Free from carcinogenic amines No health risk to dyes No risk of ban </li></ul><ul><li>High repeatability of dyeing Less shading and stripping </li></ul>
  16. 16. ECO FRIENDLY REDUCING AGENTS FOR VAT DYES <ul><li> </li></ul><ul><li>SODIUM HYDROSULPHITE IS UNIVERSALLY USED </li></ul><ul><li>DURING DYEING CONVERSION TO SULPHITE AND SULPHATE </li></ul><ul><li>SULPHITE IS TOXIC TO FISH AND BACTERIA </li></ul><ul><li>SULPHATE IS NON-TOXIC TO FISH AND BACTERIA IT MAY CAUSE CORROSION OF CONCRETE PIPES </li></ul>
  17. 17. ALTERNATE REDUCING SYSTEMS <ul><li>HYDROXY ACETONE </li></ul><ul><li>CAN TOTALLY REPLACE HYDROSULPHITE </li></ul><ul><li>BIO-COMPATIBLE </li></ul><ul><li>GIVE 20% HIGHER COLOUR YIELD WITH INDIGO </li></ul><ul><li>EXPENSIVE </li></ul><ul><li>NOT READILY AVAILABLE </li></ul><ul><li>YET TO USE ON COMMERCIAL SCALE </li></ul>
  18. 18. ELECTROCHEMICAL REDUCTION <ul><li>DIRECT REDUCTION OF DYE BY CONTACT BETWEEN DYE DISPERSION AND ELECTRODE </li></ul><ul><li>ADDITION OF SMALL QUANTITY OF HYDROSULPHITE IS ESSENTIAL TO MAINTAIN DYE IN REDUCED STATE </li></ul><ul><li>METHOD PRODUCES LIGHTER SHAED COMPARED TO HYDRO SULPHITE </li></ul>
  19. 19. IRON COMPLEXES <ul><li>USE OF Fe(OH) 2 AS REDUCING AGENT </li></ul><ul><li>COPPERAS METHOD KNOWN FOR LONG FOR DYEING OF INDIGO </li></ul><ul><li>USE OF FeSO4 AND Ca(OH)2 </li></ul><ul><li>Fe(OH)2 HAS VERY LOW WATER SOLUBILITY </li></ul><ul><li>PRECIPITATES IN DYEBATHN NO REPRODUCIBLE RESULTS </li></ul><ul><li>NOT SUITABLE FOR VAT DYES OTHER THAN INDIGO </li></ul><ul><li>USE OF GLUCONIC ACID IS SUGGESTED IN GERMAN LITERATURE FOR ENHANCING SOLUBILITY OF Fe(OH)2 </li></ul><ul><li>GLUCONIC ACID IS EXPENSIVE </li></ul>
  20. 20. STUDY AT IIT DELHI R.B.chavan, J.N.chakraborty <ul><li>USE OF CITRIC ACID, TARTARIC ACID AND TRIETHANOL AMINE TO ENHANCE SOLUBILITY OF Fe(OH)2 </li></ul><ul><li>REDUCTION POTENTIAL HIGHER THAN HYDRO SYLPHITE </li></ul><ul><li>POSSIBLE TO REDUCE VAT DYES AT ROOM TEMPERATURE </li></ul><ul><li>DYEING AT ROOM TEMPERATURE </li></ul><ul><li>COLOUR YIELD AND FASTNESS PROPERTIES COMPARABLE TO HYDROSULPHITE </li></ul><ul><li>TOTAL REPLACEMENT OF HYDROSULPHITE </li></ul><ul><li>ENVIRONMENT FRIENDLY AND ENERGY SAVING SYSTEM </li></ul>
  21. 21. SULPHUR DYES <ul><li>Na2S IS COMMONLY USED REDUCING AGENT </li></ul><ul><li>NO ODOUR NUISANCE ABOVE pH 9 </li></ul><ul><li>LIBERATION OF H2S UNDER ACID CONDITIONS </li></ul><ul><li>FOUL SMELL OF ROTTEN EGGS </li></ul><ul><li>TOXIC WHEN INHALED </li></ul><ul><li>ODOUR THRESHOLD LIMIT 10 ppm </li></ul><ul><li>TOXIC TO FISH </li></ul>
  22. 22. OXIDATION <ul><li>USE OF HALOGENATED COMPOUNDS LIKE BROMATE, IODATE PRODUCE ORGANIC HALOGEN COMPOUNDS RESPONSIBLE FOR ADSORBABLE ORGANIC HALOGEN (AOX) </li></ul><ul><li>AOX IS TOXIC TO AQUATIC LIFE </li></ul><ul><li>DICHROMATE IS MORE RISKY, HEALTH HAZARDS </li></ul><ul><li>SAFE OXIDIZING AGENT IS H 2 O 2 </li></ul>
  23. 23. Na 2 S REPLACEMENT <ul><li>β – MERCAPTOETHANOL MARKETED BY BASF AS MOLESCAL SF </li></ul><ul><li>LOWER COLOUR YIELD COMPARED TO Na2S </li></ul><ul><li>INCOMPLETE DISSOLUTION OF SOME SULPHUR DYES </li></ul><ul><li>SUITABLE FOR LIMITED RANGE OF SULPHUR DYES </li></ul><ul><li>COSTLY </li></ul>
  24. 24. <ul><li>GLUCOSE </li></ul><ul><li>CAN BE USED AS REDUCING AGENT FOR SULPHUR DYES </li></ul><ul><li>GIVES REDUCTION POTENTIAL SUITABLE FOR REDUCTION OF SULPHUR DYES UNDER ALKALINE CONDITIONS ABOVE 60 0 c </li></ul><ul><li>CENTURY MILL (MUMBAI) HAS SUCCESSFULLY REPLACED Na2S WITH GLUCOSE ON INDUSTRIAL SCALE </li></ul><ul><li>HYDROL, VISCOUS LIQUID AVAILABLE COMMERCIALLY AT LOW COST </li></ul>
  25. 25. CONCLUSION <ul><li>USE OF BIFUNCTIONAL REACTIVE DYES FOR LOW COLOUR IN EFFLUENT </li></ul><ul><li>USE OF LOW SALT REACTIVE DYES FOR REDUCTION OF SALT IN EFFLUENT </li></ul><ul><li>REPLACEMENT OF Na2S WITH GLUCOSE IN SULPHUR DYEING </li></ul><ul><li>REPLACEMENT OF HYDROSULPHITE IN VAT DYEING BY </li></ul><ul><li>IRON COMPLEXES </li></ul><ul><li>ELECTROCHEMCAL REDUCTION METHOD </li></ul>

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