Lecture 10 environment friendly dyeing of cotton
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The document discusses various methods for making cotton dyeing more environmentally friendly. It focuses on reducing the amount of dyes, salts, and other chemicals released in effluents. Some key methods mentioned are using bifunctional reactive dyes for lower color effluents, low salt reactive dyes to reduce salt, replacing sodium hydrosulfite and sodium sulfide reducing agents, and dyeing at lower liquor ratios. The goal is to meet environmental standards while maintaining dye yield and fastness properties.
Lecture 10 environment friendly dyeing of cotton
- 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. 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
- 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. ENVIRONMENT FRIENDLY DYEING DYE CLASSES FOR CELLULOSIC REACTIVE VAT DIRECT AZOIC SULPHUR EFFLUENT RESIDUAL DYE SALT ALKALI REDUCING AGENT OXIDIZING AGENT DETERGENT
- 5. REACTIVE DYES ENVIRONMENTAL PROBLEM COLOUR IN EFFLUENT SALT IN EFFLUENT
- 6. Typical dye fixation on different fibres
- 7. 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
- 8. 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
- 10. 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
- 11. 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
- 12. 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
- 13. GENERAL STRUCTURE OF LOW SALT REACTIVE DYES CHROMOPH-ORE CHROMOPHORE BRID-GE REACT-IVE GROUP REACT-IVE GROUP
- 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. 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
- 16. 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
- 17. 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
- 18. 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
- 19. 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
- 20. 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
- 21. 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
- 22. 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
- 23. 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
- 24. 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
- 25. 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