Eco- Friendliness In Textile Industry: An Eco- Friendliness In Textile Industry: An IntroductionIntroduction

The textile dyeing and finishing sector uses large volumes of The textile dyeing and finishing sector uses large volumes of water and substantial quantities of complex chemicals. water and substantial quantities of complex chemicals. Companies operating in this sector are facing significant Companies operating in this sector are facing significant challenges, many associated with the acquisition and challenges, many associated with the acquisition and disposal of these essential raw materials. In particular, the disposal of these essential raw materials. In particular, the charges incurred for main water supply and effluent disposal charges incurred for main water supply and effluent disposal are increasing, and companies need to address these issues are increasing, and companies need to address these issues to save money and remain competitive.to save money and remain competitive.

Woven Fabric FinishingWoven Fabric Finishing

Knit Fabric FinishingKnit Fabric Finishing

Stock & Yarn Dyeing & Stock & Yarn Dyeing & FinishingFinishing

The input materials used in textile dyeing and finishing can The input materials used in textile dyeing and finishing can include: water, the fibre, yarn or cloth and a range of process include: water, the fibre, yarn or cloth and a range of process chemicals including:chemicals including:

acids, eg acetic, formic;acids, eg acetic, formic; alkalis, eg sodium hydroxide, potassium hydroxide, sodium alkalis, eg sodium hydroxide, potassium hydroxide, sodium

carbonate;carbonate; bleach, eg hydrogen peroxide, sodium hypochlorite, sodium bleach, eg hydrogen peroxide, sodium hypochlorite, sodium

chlorite;chlorite; dyes, eg direct, disperse, pigment, vat;dyes, eg direct, disperse, pigment, vat; salts, eg sodium chloride;salts, eg sodium chloride; size, eg starch, PVA;size, eg starch, PVA; stabilisers, eg sodium silicate, sodium nitrate, organic stabilisers, eg sodium silicate, sodium nitrate, organic

stabilisers;stabilisers; surfactants;surfactants; auxiliary finishes, eg fire retardant, softeners (or handle auxiliary finishes, eg fire retardant, softeners (or handle

modifiers).modifiers).

POLLUTION CAUSED BY POLLUTION CAUSED BY COLORATIONCOLORATION

Discharge of Discharge of pollution from coloration pollution from coloration occurs in the following way:-occurs in the following way:-

When the dye is applied to the fabric, the When the dye is applied to the fabric, the coloring agent is not all picked by the fabric, coloring agent is not all picked by the fabric, so they act as pollutants.so they act as pollutants.

Effluent quality is determined by:Effluent quality is determined by: the level of impurities in the raw fibre prior to the level of impurities in the raw fibre prior to

processing;processing; the type and configuration of the wash the type and configuration of the wash

ranges, eg batch or continuous;ranges, eg batch or continuous; the types of chemicals used and their the types of chemicals used and their

concentration;concentration; the amount of water used and the wash-the amount of water used and the wash-

water flow rate.water flow rate.

Typical effluent Typical effluent characteristicscharacteristics

Eco-friendliness can be assured in three ways:

• by using water more efficiently to reduce the effluent volume;•by using chemicals more efficiently to reduce effluent strength;•by using alternative chemicals which reduce effluent strength and are lessdetrimental to the environment

There are three key areas of water use in textile processing:

• fabric or yarn pre-cleaning and rinsing prior to dyeing or printing;

• the dyeing or printing operation, soaping and after-treatment;

• rinsing.

OPTIONS FOR REDUCING OPTIONS FOR REDUCING WATER USEWATER USE

Repair leaks, faulty valves etcRepair leaks, faulty valves etcTurn off running taps and hosesTurn off running taps and hosesTurn off water when machines are not Turn off water when machines are not

operatingoperatingReduce the number of process stepsReduce the number of process stepsReduce process water useReduce process water useRecycle cooling waterRecycle cooling waterRe-use process waterRe-use process water

Examples of Process Water Examples of Process Water ReductionReduction

OPTIONS FOR REDUCING OPTIONS FOR REDUCING CHEMICAL USECHEMICAL USE

controlling the quantity of each chemical usedcontrolling the quantity of each chemical used recipe optimisationrecipe optimisation instruments can be installed to ensure uniformity instruments can be installed to ensure uniformity

of temperature and pressure conditions between of temperature and pressure conditions between batchesbatches

Pre-screen raw materials and chemicalsPre-screen raw materials and chemicals replacing more-polluting chemicals with less-replacing more-polluting chemicals with less-

polluting substances.polluting substances. Chemical recovery and re-useChemical recovery and re-use Improved dye fixationImproved dye fixation

Chemical recovery and re-useChemical recovery and re-use

The recovery and re-use of chemicals have The recovery and re-use of chemicals have been applied successfully in three main been applied successfully in three main areas:areas: the re-use of dye solutions from the dye bath;the re-use of dye solutions from the dye bath; the recovery of caustic after the mercerising the recovery of caustic after the mercerising

process;process; the recovery of size in cotton processing (in the recovery of size in cotton processing (in

practice this is limited to integrated operations practice this is limited to integrated operations which apply and remove size).which apply and remove size).

Dye-Bath Re-Use ApplicationsDye-Bath Re-Use Applications

Improvements in dyestuffs:Improvements in dyestuffs:fibre-reactive dyes for cellulosics, with stable fixation rates fibre-reactive dyes for cellulosics, with stable fixation rates regardless of variations in dyeing conditionsregardless of variations in dyeing conditions direct dyes with high fixation rates irrespective of variations in direct dyes with high fixation rates irrespective of variations in liquor ratio, salt or alkaliliquor ratio, salt or alkaliquantities, temperature and time;quantities, temperature and time;metal-free reactive dyes with high fixation rates and minimum metal-free reactive dyes with high fixation rates and minimum salt consumption;salt consumption; metal-free direct dyes;metal-free direct dyes; metal-free, pre-metallised and chrome dyes;metal-free, pre-metallised and chrome dyes; low-sulphide/sulphide-free dyes.low-sulphide/sulphide-free dyes.

Further improvements include:Further improvements include: granular dyestuff formulations which are easy to dissolve and granular dyestuff formulations which are easy to dissolve and handle and which reduce dust generation;handle and which reduce dust generation; the withdrawal of potentially carcinogenic azo-dyestuffs;the withdrawal of potentially carcinogenic azo-dyestuffs; dyestuffs with biodegradable formulating agentsdyestuffs with biodegradable formulating agents..

New Equipment & Cleaner New Equipment & Cleaner ProductionProduction

Reduced cleaning loss - Reduced cleaning loss - In rotary screen printing, up to In rotary screen printing, up to 8.5 kg of colour or print paste can be present in the pipe 8.5 kg of colour or print paste can be present in the pipe between the dye tank and squeegee blade. This will be between the dye tank and squeegee blade. This will be ‘lost’ when the pipe is cleaned out at changeover. ‘lost’ when the pipe is cleaned out at changeover. Reduced-diameter pipe work and reverse compressed Reduced-diameter pipe work and reverse compressed air injection have reduced this loss to just 1.5 kg.air injection have reduced this loss to just 1.5 kg.

Screen printing squeegee wash – Screen printing squeegee wash – Wash water use for Wash water use for squeegee cleaning can be reducedsqueegee cleaning can be reduced from 100 litres to 20 from 100 litres to 20 litres per squeegee by replacing manual washing with litres per squeegee by replacing manual washing with automatic high pressure water cleaning.automatic high pressure water cleaning.

Conveyor belt washwater recycling - Conveyor belt washwater recycling - Older machines Older machines

use substantial quantities of water to remove lint and use substantial quantities of water to remove lint and dye from the print machine conveyor in a blanket wash dye from the print machine conveyor in a blanket wash at the end of the line. New equipment uses staged at the end of the line. New equipment uses staged rinsing with countercurrent rinse water flow, significantly rinsing with countercurrent rinse water flow, significantly reducing water use and effluent generation.reducing water use and effluent generation.

Cleaner TechnologyCleaner Technology Single-stage desizing-scouring-bleaching processes for Single-stage desizing-scouring-bleaching processes for

processing cellulosics and their blends with synthetics.processing cellulosics and their blends with synthetics. Solvent-aided scouring and bleaching processes.Solvent-aided scouring and bleaching processes. Activated peroxide bleaching taking chemically-treated Activated peroxide bleaching taking chemically-treated

goods straight into a peroxide bath through the washing goods straight into a peroxide bath through the washing machine.machine.

Dyeing-sizing of warp yarns for denim-style products.Dyeing-sizing of warp yarns for denim-style products. Hot mercerisation in place of conventional cold Hot mercerisation in place of conventional cold

mercerisation, often enabling the elimination of separate mercerisation, often enabling the elimination of separate scouring treatment.scouring treatment.

Combined disperse and reactive/direct colour-dyeing of Combined disperse and reactive/direct colour-dyeing of blended fabrics containing low percentages of cellulosics.blended fabrics containing low percentages of cellulosics.

Use of padding method in place of exhaust methods for Use of padding method in place of exhaust methods for dyeing, wherever possible.dyeing, wherever possible.

Use of bicarbonate in a peroxide bath for vat oxidation Use of bicarbonate in a peroxide bath for vat oxidation to convert caustic alkalinity into carbonate alkalinity for to convert caustic alkalinity into carbonate alkalinity for its easier removal. Alkalinity requires a plentiful supply its easier removal. Alkalinity requires a plentiful supply of water.of water.

Electrolytic process for the dyeing of vat colours and Electrolytic process for the dyeing of vat colours and reduction-clearing of disperse-colourprinted synthetic reduction-clearing of disperse-colourprinted synthetic fabrics.fabrics.

Dry-heat fixation techniques for the development of Dry-heat fixation techniques for the development of Rapidogen prints in place of the conventional acid-Rapidogen prints in place of the conventional acid-steaming method.steaming method.

Effluent Treatment Effluent Treatment

Options for effluent treatment include:Options for effluent treatment include: biological/biosorption techniques;biological/biosorption techniques; ultrafiltration;ultrafiltration; ion exchange;ion exchange; reverse osmosis;reverse osmosis; adsorption;adsorption; coagulation/flocculation;coagulation/flocculation; chemical oxidation;chemical oxidation; photocatalytic oxidation;photocatalytic oxidation; electrolysis.electrolysis.

ConclusionConclusion

Low water and effluent disposal costs have Low water and effluent disposal costs have resulted in overuse and wasteful practices resulted in overuse and wasteful practices throughout industry. Now that effluent throughout industry. Now that effluent disposal (and chemical) costs are rising, disposal (and chemical) costs are rising, many companies are, almost literally, many companies are, almost literally, throwing money down the drain.throwing money down the drain.Eco-friendliness has to be taken care of for Eco-friendliness has to be taken care of for the conducive existence of the natural and the conducive existence of the natural and the man-made.the man-made.