R.B.CHAVAN I.I.T.DELHI 1

ENVIRONMENT FRIENDLY DYEING PROCESSES FOR COTTON

R.B.CHAVAN

DEPARTMENT OF TEXTILE TECHNOLOGY

INDIAN INSTITUTE OF TECHNOLOGY

HAUZ-KHAS, NEW DELHI 110016

R.B.CHAVAN I.I.T.DELHI 2

PLANATE EARTH

KALPANA CHAWLA• IT IS THE ONLY PLANATE WHERE LIFE

EXISTS

• FROM THE SPACE EARTH LOOKS BEAUTIFUL

• OUR ENDEVOUR SHOULD BE TO ENHANCE THE BEAUTY OF THIS PLANATE

• ALL EFFORTS SHOULD BE MADE TO PROTECT IT FROM DESTRUCTION

R.B.CHAVAN I.I.T.DELHI 3

DESTRUCTIVE FORCES

• ONE TIME DESTRUCTION• NUCLEAR THREAT• RED BUTTON SHOULD BE IN THE HANDS OF BALANCED

PERSONS

• SLOW DEATH• ENVIRONMENT POLLUTION• OZONE DEPLETION• ULTRA VIOLET PROTECTION• VEHICULAR AIR POLLUTION• NUCLEAR AND BIOLOGICAL WASTE• ASIAN BROWN CLOUD (INCOMPLETE COMBUSTION OF

WOOD, COW DUNG CAKES ETC.• INDUSTRIAL ACTIVITIES

R.B.CHAVAN I.I.T.DELHI 4

INDIAN EXPERIENCE

• AIR POLLUTION : VEHICLE• BAN ON 15 YEAR OLD PUBLIC TRANSPOT

VEHICLES • USE OF CNG

• CLEAN AIR IN DELHI

• GANGA RIVER PROJECT: CLEAN WATER

• FOREST PROTECTION

R.B.CHAVAN I.I.T.DELHI 5

CUMULATIVE EFFECT

• INDUSTRIAL ACTIVITIES• LARGE SCALE• SMALL SCALE• COTTAGE SCALE• TRADITIONAL• CUMULATIVE EFFECT ON ENVIRONMENT

POLLUTION• ATTEMPTS TO MINIMIZE POLLUTION• USE OF NEWER TECHNOLOGIES

R.B.CHAVAN I.I.T.DELHI 6

WORD FIBRE CONSUMPTION

CONSUMPTION (1000 TONNE)

YEAR COTTON REGENERATED WOOL SYNTHETIC

TOTAL

1990 18700

(49%)

2700 2000 14900

(39%)

39300

1995 20700

(49%)

2500 2000 17300

(41%)

42600

2000 23400

(49%)

2400 2200 20500

(42%)

48500

R.B.CHAVAN I.I.T.DELHI 7

DYE CONSUMPTION (TONNE)

DYE CLASS 1988a 1992 2004b

SULPHUR 90 000 70 000 70 000DIRECT 74 000 60 000 68 000VAT 36 000 21 000 22 000

INDIGO 12 000 12 000 12 000

AZOIC 28 000 18 000 13 000

REACTIVE 60 000 109 000 178 000

TOTAL 300 000 290 000 354 000

R.B.CHAVAN I.I.T.DELHI 8

REASONS FOR LACK OF GROWTH EXCEPT REACTIVE DYES

VAT DYES• HIGH PRICE AND LIMITED SUPPLY

ENVIRONMENT

• VAT: HYDROSULPHITE, ORGANIC HALOGEN,RESIDUAL METAL CATALYST

• SULPHUR : SODIUM SULPHIDE,

• AZOIC : CARCINOGENIC AMINE

R.B.CHAVAN I.I.T.DELHI 9

CURRENT RESEARCH

MAJOR AREAS1. ENVIRONMENTAL CONSIDERATIONS

• LOW COLOUR IN EFFLUENT

• LESS CHEMICAL USAGE

2. INCREASED PRODUCTIVITY VIA SHORTER AND RELIABLE PROCESSING

3. HIGHER FASTNESS REQUIREMENTS

R.B.CHAVAN I.I.T.DELHI 10

Chemicals in effluent streams

Chemicals in effluent streams

• Vat Residual dyestuff (5 - 20 %)

Reducing agents

Oxidising agents

Detergents

Salt

• Reactive Residual dyestuff (20 - 50 %)

Salt

Alkali

Detergent

R.B.CHAVAN I.I.T.DELHI 11

Chemicals in effluent streams

• Direct Residual dyestuff (5 - 20 %)

Salt

Dye fixing agents

• Sulphur Residual dyestuff (30 - 40 %)

Sodium sulphide

Alkali

Salt

R.B.CHAVAN I.I.T.DELHI 12

Chemicals in effluent streams• Acid Residual dyestuff (1 - 20 %)  Organic acid• Metal complex Residual dyestuff (2 - 5 %) Organic acid Leveling agent • Chrome Organic acid Heavy metal

• Disperse Residual dyestuff (10 - 20 %)AcidDispersing agentsLeveling agentsReducing agentsAlkali

 

 

R.B.CHAVAN I.I.T.DELHI 13

COLOUR IN EFFLUENT

END OF PIPE TECHNOLOGY

• REMOVAL OF COLOUR FROM EFFLUENT – EXPENSIVE APPROACH

• CONVENTIONAL REACTIVE DYES 60-

70% EXHAUSTION

• SUBSTANTIAL COLOUR IN EFFLUENT

• ADSOPTION OF HYDROLYZED DYE

ON BIOMASS IS NOT EFFICIENT

R.B.CHAVAN I.I.T.DELHI 14

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

R.B.CHAVAN I.I.T.DELHI 15

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

R.B.CHAVAN I.I.T.DELHI 16

BIFUNCTIONAL REACTIVE DYES

R.B.CHAVAN I.I.T.DELHI 17

LOW SALT REACTIVE DYES

SALT REQUIREMENTCONVENTIONAL 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

R.B.CHAVAN I.I.T.DELHI 18

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

R.B.CHAVAN I.I.T.DELHI 19

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

R.B.CHAVAN I.I.T.DELHI 20

GENERAL STRUCTURE OF LOW SALT REACTIVE DYES

CHROMOPH-ORE

CHROMOPHORE

BRID-GE

REACT-IVE

GROUP

REACT-IVE

GROUP

R.B.CHAVAN I.I.T.DELHI 21

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

R.B.CHAVAN I.I.T.DELHI 22

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

R.B.CHAVAN I.I.T.DELHI 23

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

R.B.CHAVAN I.I.T.DELHI 24

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

R.B.CHAVAN I.I.T.DELHI 25

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 TPO HYDRO SULPHITE

R.B.CHAVAN I.I.T.DELHI 26

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 DYEBATHNON 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

R.B.CHAVAN I.I.T.DELHI 27

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

R.B.CHAVAN I.I.T.DELHI 28

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

R.B.CHAVAN I.I.T.DELHI 29

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

R.B.CHAVAN I.I.T.DELHI 30

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

R.B.CHAVAN I.I.T.DELHI 31

• GLUCOSE• CAN BE USED AS REDUCING AGENT FOR

SULPHUR DYES

• GIVES REDUCTION POTENTIAL SUITABLE FOR REDUCTION OF SULPHUR DYES UNDER ALKALINE CONDITIONS AT ABOVE 600 c

• CENTURY MILL (MUMBAI) HAS SUCCESSFULLY REPLACED Na2S WITH GLUCOSE ON INDUSTRIAL SCALE

• HYDROL, VISCOUS LIQUID AVAILABLE COMMERCIALLY AT LOW COST

R.B.CHAVAN I.I.T.DELHI 32

HYDROL/GLUCOSE

• HYDROL IS COST EFFECTIVE ENVIRONMENT FRIENDLY SUBSTITURE OF Na2S

• ELIMINATION OF FOUL SMELL OF NA2S

• 3500 kg OF COTTON IS BEING DYED WITH SULPHUR BLACK EVERY DAY USING HYDROL AT CENTURY MILL

• NO CAPITAL EXPENDITURE INVOLVED IN THIS SUBSTITUTION

R.B.CHAVAN I.I.T.DELHI 33

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