ENVIRONMENT FRIENDLY DYEING OF COTTON R.B.CHAVAN Department of Textile Technology Indian Institute of Technology Hauz-khas, New Delhi 110016 E-mail: [email protected]
May 10, 2015
ENVIRONMENT FRIENDLY DYEING OF COTTON
R.B.CHAVAN
Department of Textile Technology
Indian Institute of Technology
Hauz-khas, New Delhi 110016
E-mail: [email protected]
PRESENT CONCEPTPOLLUTERS 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 EnergyNatural Fibres; 10-20 MJ/kgChemical Fibres: 5-50 MJ/kg
Water60-360 l/kg textile
Polluted Air
Water Effluent
WasteSewage 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 60-800 c• BETTER SHADE REPRODUCIBILITY EVEN WITH
TEMPERATURE VARIATION• AVAILABLE FROM MAJOR DYESTUFF MANUFACTURERES
BIFUNCTIONAL REACTIVE DYES
LOW SALT REACTIVE DYES
SALT REQUIREMENTCONVENTIONAL REACTIVE DYES 60-80 g/lLOW 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 dyes60 % 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 energyLow 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 DELHIR.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 H2O2
Na2S 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 600 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 DYEINGREPLACEMENT OF HYDROSULPHITE IN VAT DYEING BY
• IRON COMPLEXES
• ELECTROCHEMCAL REDUCTION METHOD