Conference PaperPDF Available

Green chemistry in Textile Industry

Authors:
  • KPS Institute of Polytechnic

Abstract

Conventional chemical processes based on fossil fuels are unsustainable. Green reactions are sustainable, more efficient (fewer steps, fewer resources, less waste), easier to use (stable under ambient conditions), eco-friendly (non-hazardous solvents and less hazardous waste). They are assessed by twelve principles, the most important being the amount of waste generated. The textile industry is considered as the most ecologically harmful industry in the world. Recently a number of steps have been taken to make textile processing greener. These include use of greener fibre, greener dyes and auxiliaries, greener solvents, eco-friendly, optimised and efficient processing, bio-processing, recycling of textile, water and chemicals and elimination of hazardous chemicals.
Green Chemistry in Textile Industry
Dr. Asim Kumar Roy Choudhury
Professor,
Govt. College of Engg. & Textile Technology, Serampore - 712201, Hooghly (W.B.) India
E-mail: akrc2008@yahoo.in
ABSTRACT:
Conventional chemical processes based on fossil fuels are unsustainable. Green reactions are
sustainable, more efficient (fewer steps, fewer resources, less waste), easier to use (stable under
ambient conditions), eco-friendly (non-hazardous solvents and less hazardous waste). They are
assessed by twelve principles, the most important being the amount of waste generated. The textile
industry is considered as the most ecologically harmful industry in the world. Recently a number of
steps have been taken to make textile processing greener. These include use of greener fibre,
greener dyes and auxiliaries, greener solvents, eco-friendly, optimised and efficient processing, bio-
processing, recycling of textile, water and chemicals and elimination of hazardous chemicals.
INTRODUCTION
Our environmental troubles are growing very fast because people perform chemistry in different ways
than Mother Nature does. For ages, biochemical processes to create everything in this world have
evolved the elements that are abundant and close at hand—such as carbon, hydrogen, oxygen,
nitrogen, sulphur, calcium and iron. Our industries, in contrast, gather elements from nearly every
corner of the planet and distribute them in ways natural processes never could. Lead, for example,
used to be found mostly in deposits so isolated and remote that nature never folded it into living
organisms. But now lead is everywhere, primarily because our paints, cars and computers have
spread it around. Some of the new synthetic molecules in medicines, plastics and pesticides are so
different from the products of natural chemistry as if they are dropped in from an alien world [1].
The hazardous substances may be categorised on the basis of chemical behaviour as follows:
1) Combustible and flammable substances
2) Oxidisers
3) Reactive substances
4) Corrosive substances
Some hazardous substances fall into more than one of these groups and are very dangerous. Often
the greatest concern with hazardous substances is their toxicity.
Toxic substances are not so easy to classify in terms of chemical properties and are more appropriate
to classify on the basis of their biochemical properties. Three kinds of toxic substances are identified
in the practice of green chemistry namely:
1) Non-destructible heavy metals, such as lead, mercury, or cadmium having a wide range of
adverse biological effects.
2) Persistent non-biodegradable organic materials, such as polychlorinated biphenyls, PCBs. Often
not extremely toxic, these substances persist in the environment adversely affecting organisms.
3) Volatile organic compounds (VOCs) used as solvents for organic reactions, vehicles in paints and
coatings, and for cleaning machine parts.
There are two basic types of materials in nature:
1) Renewable: The materials those grow and are biodegradable and they re-grow,
2) Non-renewable: The materials that are finite and do not grow. The excessive use of non-
renewable materials is unsustainable.
The conventional chemical manufacturing processes are unsustainable because:
(a) Mostly carbon-based products are derived from fossil fuels, petroleum and coal which have
limited supply.
(b) Large amounts of waste increasing burden on the environment.
GREEN CHEMISTRY
Environmental chemistry studies the effect of environmental pollutants, whereas green chemistry
deals with new sciences and technologies to prevent the formation of any waste. The principles of
green chemistry offer an upstream solution to many of the health, environmental, and economic
problems related to industrial chemicals [3]. To date, producers have not invested in green chemistry
at a level commensurate with the scale and pace of chemical production [4].
The green issues are being confused with ‘organic’ sourcing and production. Indeed, many people are
unaware that some of the most toxic chemicals known (e.g. ricin and botulin) are not manufactured
but are natural proteins [5].
1
In conventional environmental systems analysis, such as environmental impact assessment, the
system boundary is drawn around a manufacturing site or a plant, whereas in Life Cycle Analysis
(LCA), the boundary is set to encompass various life-cycle stages [6] namely extraction and
processing of raw materials, manufacturing, transportation and distribution, use, reuse and
maintenance, recycling, final disposal.
Cleaner production is the conceptual and procedural approach to production that demands that all
phases of the life-cycle of a product or of a process should be addressed with the objective of
prevention or the minimization of short and long term risks to humans and the environment.
The green chemistry concept solves the pollution prevention problem at the molecular level by
focusing on chemicals whereas clean technologies deals mainly with processes such as separation
for recycling, recovery, conservation, and rational use of raw materials, water and energy,
optimization of production processes, disposal or recycling of unavoidable waste. In this sense, green
chemistry is complementary to clean technology which is based on chemical engineering rather than
pure chemistry [7].
Principles of Green Chemistry
Twelve principles of green chemistry are:
1) Use renewable feedstock.
2) Use safe or non-toxic but fully effective products
3) Use safe chemical synthesis methods
4) Adopt catalytic reactions to minimise waste. Gold is an outstanding catalyst for oxidation
processes [10].
5) Use energy efficient processes - prefer ambient temperature and pressure reactions
6) Use safer solvents and auxiliaries - use aqueous or other safe media.
7) Omit sequential chemical steps - choose direct reactions.
8) Follow atom economy: There should be few, if any, wasted atoms.
9) Prevent waste - eliminate/minimise waste treatment processes.
10) Use chemical products those are easy degradable to harmless substances.
11) Real time analysis - Minimise/eliminate by-products by real-time monitoring and control.
12) Safety - assure minimum chemical accidents (e.g. explosions, fires and harmful releases).
Focus areas
Sustainable (green) chemistry technologies can be categorised into the following three focus areas:
1) Alternative synthesis routes,
2) Alternative reaction conditions, and
3) The use of safer chemicals - less toxic or less accident prone.
Catalysis can not only help to green chemical processes (e.g., by replacing reagents or by enabling
more efficient processes) but also reduce the environmental impact and the costs of the processes.
The heterogenisation of catalysts (and, where appropriate, reagents) so that they can easily be
separated (and reused) at the end of a process, is a logical and versatile approach to simplifying the
process, removing the need for an aqueous quench (or other destructive separation step) and
reducing the demand for raw materials.
Green Solvents
Liquid solvents are by far the most common type of media in which reagents are dissolved. Solvents
cause more environmental and health problems than do the reagents in the chemical synthesis
process. Most solvents are volatile and tend to escape into the workplace and atmosphere.
Hydrocarbon solvents are flammable and can cause explosive mixtures with air. Carbon tetrachloride
causes lipid peroxidation in the body and severe damage to the liver and also causes stratospheric
ozone destruction. The possibility of causing cancer is always a consideration in dealing with solvents
in the workplace.
The use of organic solvents consisting of hydrocarbons and hydrocarbon derivatives, such as
chlorinated hydrocarbons, is unavoidable in many cases. In addition to serving as reaction media,
organic solvents are used as cleaners, degreasers, and for extraction of organic substances from
solids. Perchloroethylene and other toxic organic solvents generally used in dry cleaning. Studies
have linked prolonged perchloroethylene exposure to liver or kidney damage; short-term contact can
cause headaches, nausea, and irritation of the skin, eyes, nose and throat. Special concern must be
taken to avoid the use of these hazardous substances by conservators and to minimize the emission
of these compounds. Some of the solvents and their eco-friendly substitutes are listed in Table 1 [11].
Table 1. Eco-friendly substitutes of a few commonly used solvents
Solvent Disadvantage Substitute Characteristics of the substitute
2
Benzene Toxic, suspected of
causing leukaemia
Toluene Much less toxic due to the
presence of a metabolically
oxidisable methyl substituent
group.
n-Hexane
Neuro-toxic causing
peripheral neuropathy –
loss of mobility, reduced
sensations
2,5-Dimethyl-
hexane
Not toxic like n-hexane. However,
significantly higher boiling point
may be a disadvantage.
Glycol
ethers
adverse reproductive and
developmental effects in
animals
1-Methoxy-
2-propanol
Less toxic than the glycol ethers,
but still effective as a solvent.
Various
organic
solvents
Flammability, toxicity,
poor biodegradability,
create photochemical
smog
Supercritical
fluid carbon
dioxide
Good solvent for organic solutes,
readily removed by evaporation,
non-polluting, except as a
greenhouse if allowed to escape.
Some green solvents are:
1) Ester solvents (volatile and non-volatile) used as carrier oils, plasticisers and coalescent e.g.
Isopropyllaurate, rapeseed methyl ester (biodiesel), glycerol triacetate, dibasic ester etc.
2) Speciality solvents e.g. glycerol carbonate, dioctylether, ethyl lactate, 2-ethylhexyl lactate etc.
3) Supercritical gases e.g. supercritical carbon dioxide.
4) Fusible solids namely:
a) Waxes e.g. hydrogenated castor oil, stearyl stearate
b) Ionic liquids e.g. tricaprylmethyl ammonium chloride, 1-butyl-3-methyl imidazollum methyl
sulphate etc.
Besides low molecular weight ester solvents, such as methyl acetate or n-butyl propionate, higher
molecular weight fatty acid esters have already found a broad acceptance as phthalate-free
plasticizers and as biodegradable carrier oils for green inks [12].
Ash and Ash [13] recommended the following solvents as green solvents:
Acetic acid, acetophenone, benzyl benzoate, diethylene glycol dibutyl ether, diethylene glycol
dimethyl ether, dimethyl sulfoxide. ethyl acetate, ethylene glycol dimethyl ether. glycerol, hexane,
methanol, polyglycol E 200, propylene glycol, t-butanol and tetrahydrofuran.
Water is the most abundant and one of the main objectives of the practice of green chemistry is to use
water as solvent wherever possible. However, water is not a suitable solvent for a wide range of
organic substances used industrially. Hydrophobic organic substances are not dissolved, but may be
held in suspension as finely divided colloidal matter. Water suffers from the disadvantage of reacting
strongly with some reagents, such as AlCl3 used in Friedel-Crafts reactions. On the other hand,
precisely because water is such a poor solvent for organic substances (the hydrophobic effect), some
organic reactions proceed better in a water medium. It is excellent solvent for hydrophilic biological
molecules, such as glucose, thereby gaining favour as reactants for green chemical processes.
Ionic Liquids
Ionic liquids are, quite simply, liquids those are composed entirely of ions. Thus, molten sodium
chloride is an ionic liquid while a solution of sodium chloride in water (a molecular solvent) is an ionic
solution [14]. Regardless of whether polar or non-polar, the common solvents (e.g., water, ethanol,
benzene, etc.) are generally molecular liquids. However, since the early 1980s an exciting new class
of liquids called room-temperature ionic liquids (RTILs) has become available. By definition, they are
salts that are liquid over a wide range of temperature and melt below about 100 ºC [15]. They are
basically constituted of ions and when they are used as solvents, they behave differently from
molecular liquids. The majority consist of nitrogen-containing organic cations and inorganic anions.
The most commonly studied systems contain phosphonium, imidazolinium or tricaprylmethyl
ammonium cations, with varying heteroatom functionality. Ionic liquids are considered green
(environmentally benign) reaction media because they are low-viscosity liquids with no measurable
vapour pressure and excellent thermal stability. They are highly conductive and have high dissolving
power for a wide variety of organic and inorganic compounds. Ionic liquids have found uses in four
distinct areas: chemical synthesis, catalysis, separation science, and electrochemistry. Ionic liquids
have created particular scientific interest for extraction or separation technologies, and phase transfer
catalysis. However, the lack of sustainable techniques for the removal of products from RTILs has
limited their application.
3
Despite all the recent research attention given to RTILs, there is still a serious lack of physical
scientific data. Comprehensive studies dealing with the toxicity, biodegradation, safety, and
environmental risk and impact of ionic liquids are needed. RTILs have to be less expensive, cleaner,
and easier to purify [16].
Green Chemicals
The ecosphere is a closed system with the limited resources of energy and raw materials and
inadequate ability to accumulate or assimilate the pollutants. Therefore uncontrolled exploitation of the
water, air, and resources may lead to irreversible degradation, and even global catastrophe.
The development of environmentally-improved routes and the design of green chemicals are two
facets of green chemistry devoted to reducing the impact of chemical processes and compounds on
the environment. Green chemicals should meet the following criteria:
1) Prepared from renewable or readily available resources by environmentally friendly processes
2) Low tendency to undergo sudden, violent, unpredictable reactions such as explosions that may
cause damage, injure personnel, or cause release of chemicals and byproducts to the
environment.
3) Non-flammable or poorly flammable
4) Low toxicity
5) Absence of toxic or environmentally dangerous constituents, particularly heavy metals
6) Facile degradability, especially biodegradability, in the environment.
7) Low tendency to undergo bioaccumulation in food chains in the environment
Dichlorodifluoromethane, one of the least toxic synthetic compounds, is definitely not green because it
is so extremely stable and persistent in the atmosphere and can cause stratospheric ozone
destruction. Much more ‘greener’ substitutes, hydrofluorocarbons and hydrochlorofluorocarbons, do
not last long when released in the atmosphere or do not contain ozone-damaging chlorine. Stable
bonds contribute to persistence and ultimate cause environmental harm.
Sodium stearate, common hand soap is a green compound, prepared by reacting by-product animal
fat with sodium hydroxide, which is prepared by passing an electrical current through saltwater.
Sodium stearate reacts with calcium in water to form a solid, calcium stearate. The non-toxic calcium
stearate readily undergoes biodegradation so that it does not persist in the environment.
Greener Energy
The processes like heating, cooling, stirring, distillation, compression, pumping, separation etc.
require energy in the form of electrical energy which is obtained by burning of fossil fuel. This results
in release of carbon dioxide in the atmosphere causing global warming. Green chemistry will be
essential in developing the alternatives for energy generation (photovoltaics, hydrogen, fuel cells, bio-
based fuels, etc.) as well as to continue the path toward energy efficiency with catalysis and product
design at the forefront.
Carbon dioxide is of major concern as a greenhouse gas because there is no doubt that human
activities are leading to a gradual increase in the atmospheric carbon dioxide level. This suggests that
we may eventually modify the global climate. Fossil fuel burning is the main contributor to the global
annual emissions, which have increased by a factor of about 10 since 1900 to an enormous 6.1 x 109
tonnes in 1994. Deforestation adds about another 1.6 x 109 tonnes per annum. This must be
considered in relation to the total atmospheric content of CO2 which is about 750 x 109 tonnes,
corresponding to a concentration of around 358 ppmv (‘v’ stands for volume concentration) in 1994
as opposed to 280 ppmv in pre-industrial times. The various components of the overall global balance
of carbon dioxide are generally understood but not easily quantified.
From the point view of green chemistry, combustion of fuels obtained from renewable feedstocks is
more preferable than combustion of fossil fuels from depleting finite sources. For example, many
vehicles around the world are fuelled with diesel oil, and the production of biodiesel oil is a promising
possibility. As the name indicates, biodiesel oil is produced from cultivated plants oil, e.g. from soya-
beans. It is synthesized from fats embedded in plant oils by removing the glycerine molecule - a
valuable raw material for soap production [17]. The combustion of biodiesel does not generate sulphur
compounds and generally does not increase the amount of carbon dioxide in the atmosphere.
Biomass, a renewable energy source, is biological material from living, or recently living organisms,
such as wood, forest residues for example (such as dead trees, branches and tree stumps), waste,
(hydrogen) gas, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or
produce heat.
As far as possible fossil derived feedstocks must be substituted and renewable feedstocks, mostly
plant derived, must be developed. The largest amount of such plant derived materials is biomass.
There is a renewed interest in the use of biomass for production of fuels and of basic chemicals and
solvents. When combined with biotechnological methods biomass may become the carbon source for
4
the production of advanced intermediates or final products. Materials obtained from renewable
specific production, namely vegetable oils or starch and traditional natural products, as carotenoids or
quinine are now receiving special attention [18].
Biomass has a broadening range of sources of waste including sewage, crops, municipal waste,
plants (forest/grass), and pulp and paper. The organic matter in the biomass is mostly cellulose,
lignins, and fatty acids. This matter can be converted into a variety of products including fuel, fine
chemicals, pharmaceuticals, polymers, and personal care products.
Evaluation of Green Reactions
To judge the general efficiency of a chemical transformation we can use the concept of atom
economy in addition to the obtained chemical yield..
Atom economy is defined as follows [11]:
The concept of atom economy can be illustrated in general by the reaction,
(reagent)1 +...+ (reagent)n product + by-product (3)
The ultimate in atom economy is achieved when there is no by-product and all the reagents are
contained within the product. Although this is often not achievable in practice, it is desirable to devise
reaction schemes such that
by-product << product (4)
One of the greater needs in chemical research today is the development of reactions for synthesis
that have a high degree of atom economy. To measure the atom economy of a reaction, the masses
of the atoms of all starting materials and reagents according to the stoichiometric equation are added
and are compared with the sum of the masses of all atoms found in the desired product. Atoms of
undesired side products and reaction by-products count as waste. The concept was introduced by
Trost [19]. The method gives a general measure of the efficiency of a reaction. The concept leads to
the conclusion that e.g. addition reactions show better atom economy than condensation or
substitution reactions, which generate stoichiometric amounts of an unwanted product.
While atom economy focus on the reaction only, Sheldon factor of environmental acceptability, E
factor [20] assesses how green a chemical process by measuring the amount of waste generated. E
factor measures the ratio of the mass of waste to that of the product. All processes should aim for the
lowest possible E factor - for truly green processes,
the E factor should be zero. Large-scale
manufacturing units for bulk chemicals may generate
large amount of waste, but their E factors may be
smaller than those of small-scale units as it depends
on the quantity of waste in relation to total production.
If established chemical production processes are
analyzed by these methods, not unexpectedly, a
correlation between environmental acceptability and
production scale is noticed (Table 2).
Advantages of Green Reactions
The advantages of adopting green chemistry [21] are:
1) Increased profits by saving reagents, solvents, energy, waste disposal costs, personnel costs,
and increasing production.
2) Universal application as any industrial process involves basics namely raw materials, chemical
reactions, solvents, and separation/purifications controllable by green chemistry.
3) Green chemistry often remains unchanged for long periods of time.
4) New separation techniques such as carbon dioxide extraction, phase separation, evaporation,
membrane separation, and reforming by-products into new products minimise waste generation.
However, a perfectly green process may not be actually green unless applied in right situations.
Challenges for Green Chemistry
The challenges for green chemistry are the identification of
1) Renewable feedstock, preferably non-food plants and its full conversion to useful products,
2) Reactions having minimum environmental impact e.g. use of eco-friendly organic catalysts.
3) Industrial processes and reactors having maximum efficiency and minimum waste,
4) Products of reduced toxicity and increased biodegradability [22]. Perhaps the greatest challenge
facing green chemists is the eventual elimination of all environmentally harmful chemical
products. Chemists are still a long way from being able to predict the properties, both chemical
and biological, of compounds from its chemical structure.
5
(2)
generated materials of mass molecular Total
product desired of mass Molecular
economy Atom
=
Table 2. Environmental Acceptability (E
Factor) of Various Industries
Industrial chemical process E factor
Oil refining 0.1
Commodity chemicals < 1.5
Special chemicals 5 - 50
Drugs 25 - >100
5) Phasing out of the flammable, toxic and volatile solvents polluting atmosphere and evaluation of
cleaner solvents as replacements [23].
GREEN CHEMISTRY IN TEXTILE INDUSTRY
The following five issues make the life cycles of textiles and clothing unsustainable [24]:
1) Use of water - textile industry is characterized by the intensive use of water and wide spectrum of
processing chemicals. Consequently, textile industrial effluents are characterised by high
chemical oxygen demand (COD) and the presence of non-biodegradable components such as
dyes, pigments and newly introduced sizing polymers. The presence of heavy metals may also be
encountered in numerous situations.
2) Use of chemicals - the pesticides and herbicides in agriculture and the toxic chemicals in
production are used recklessly.
3) Use of non-renewable energy in production - non-renewable energy sources are undervalued and
are used non-regulatorily. The largest environmental impact of textiles occurs during their use by
consumers (75-95% of total environmental impact) and is mainly accounted for the use of
electricity to heat water for running laundry and to dry materials after laundering.
4) Waste generation - the generation of a huge quantity of waste – non-renewable are to be recycled
and renewable are to be composted as much as possible.
5) Energy for transport - to utilise the benefit of cheap labour, land etc. the production units are far
away from consumer point resulting use of excessive non-renewable fuel in transport.
The achievement of delivering sustainable textile products is tarnished when it is packed with huge
quantity of plastics and layers of foam. Recyclable and reusable packaging materials will improve
sustainability of the products.
In paper and textile industries, efforts are being made to develop new greener methods, which result
in reduction in energy, water usage, time in textile processing.
Greener Fibres
Cotton represents almost 38% of the world’s textile consumption, second only to polyester. Cotton is
highly susceptible to pests, especially in humid areas. Though cotton production is restricted to 2.4%
of cultivable land globally, an estimated 25% of global insecticide and 11% of global pesticide are
consumed in its cultivation. This ‘thirsty’ crop also requires 7000-29000 litres of water to produce one
kg of cotton fibre [25].
Organic cotton is generally understood as cotton, from non-genetically-modified plants, that is certified
to be grown without the use of any synthetic agricultural chemicals such as fertilizers or pesticides. In
order to protect organic integrity, all post-harvest processing, storage and transport of organic cotton
fibre products should be segregated from conventional cotton and should not come in contact with
prohibited materials or other contaminants. The treatments should be preferably done with natural
dyes and chemicals and enzymes. Lists of permitted synthetic and non-synthetic chemicals are
declared in eco-labels like GOTS. Similarly, ‘organic linen’ refers to linen that is made from flax fibres
grown without the use of toxic pesticides and fertilizers (http://www.natural-environment.com).
Although wool itself is a natural fibre, traditional wool production is not known for it’s eco-friendliness.
Generally speaking, by selecting organic wool, it is ensured that the wool has been produced in a
much more natural and sustainable way, compared to non-organic wool.
Different countries have different standards regarding organic certification. In some countries, the
standards are set and overseen by the government. In other countries, the standards are set by a
non-profit organization or even a private company. In North America, for certifying wool as organic by
Organic Trade Association (OTA, it must adhere to the following requirements:
Livestock feed and fodder used from the last third of gestation must be certified organic,
Use of synthetic hormones and genetic engineering is prohibited,
Use of synthetic pesticides (internal, external, and on pastures) is prohibited, and
Producers must encourage livestock health through good cultural and management practices
(www.natural-environment.com).
Lyocell fibres are produced by regenerating cellulose in an organic solvent, N-methylmorpholine-N-
oxide (NMMO) hydrate. Non-toxic, biodegradable NMMO solvent used is almost completely recycled
[26]. The fibre is significantly more sustainable than oil-derived synthetic fibres and natural fibres such
as cotton (need pesticides and fertilisers to grow). Land required for cotton is more than the
eucalyptus trees, from which lyocell is made [27].
The process of regenerating the cellulose can be greatly simplified by the use of ionic liquids which
serve as the solvent and can be almost entirely recycled. A truly green ionic liquid would need to be
sustainable, easy and clean to prepare, non-toxic and biodegradable [28].
Bamboo fibre has particular and natural functions of anti-bacteria, bacteriostasis and deodorisation. It
is validated by Japan Textile Inspection Association that, even after fifty times of washing, bamboo
6
fibre fabric still possesses excellent function of anti-bacteria, bacteriostasis. Like chemical
antimicrobial, it does not cause skin allergy. The bamboo fibres are claimed to be very soft, taking dye
to deeper shades than cotton and having natural antimicrobial properties. It was said to grow without
pesticides and is far more eco-friendly than cotton and other fibres [29].
Large quantity of adipic acid (HOOC(CH2)4COOH) is used for the production of nylon, polyurethanes,
lubricants and plasticizers. This is produced from benzene - a compound with convinced carcinogenic
properties. Chemists from State University of Michigan developed green synthesis of adipic acid using
a less toxic substrate. Furthermore, the natural source of this raw material, glucose, is almost
inexhaustible. The glucose can be converted into adipic acid by an enzyme discovered in genetically
modified bacteria [30]. This green route of production guards the workers and the environment from
exposure to hazardous chemical compounds.
Polyurethane polymers are extremely important and versatile materials having numerous applications
in foams, surface and textile coatings, adhesives and elastomers. The synthesis of polyurethane
polymers avoiding or minimising the requirement for toxic diisocyanate is reported. Using the Candida
antarctica lipase B to catalyse the polyesterification, a series of polyurethanes based on bis-
carbamate diols were synthesised. Several polyurethane polymers have been synthesised based on
diamines for which no corresponding diisocyanate exists [31].
The manufacture of synthetic polymers consumes large quantities of petroleum for raw material, and
synthetic and natural polymers make up a large fraction of solid waste. For
these reasons, it is desirable to make both polymers from renewable
biological sources and to synthesize and use polymers that will biodegrade
after disposal. Nature has provided a large variety of polymer such as
cellulose in wood and cotton, lignin in wood, and protein in wool and silk.
With the exception of degradation-resistant lignin, these polymers, made
by organisms, are also degradable by organisms, particularly fungi and
bacteria.
Bio-polymers
The use of biopolymers, i.e. plastics made from corn, sugar, starch and other renewable raw
materials, has exploded in recent years. Henry Ford first used soy plastic to construct various car
parts. Cargiil Dow's wonderful and well-known technology uses corn to produce polylactic acid. It's a
marvellous process that consumes up to 50% less fossil fuel than conventional PLA manufacturing
processes using petroleum-based feedstocks. It produces no toxic wastes, and its end products are
biodegradable.
Corn starch unrefined dextrose fermentation lactic acid monomer production lactide
polymer (PLA) production polymer modification fibre, film, plastic, bottle etc.
Due to its high strength, polylactic acid (PLA) can be fabricated into fibres, films, and rods that are
fully biodegradable (lactic acid, CO2) and compostable, since they degrade within 45–60 days.
Cornhusks, collected from fully mature corn plants, are cleaned and are cut in order to obtain fibres
that had lengths similar to cotton and suitable for processing on the cotton spinning system. The
structure and properties of corn fibres are similar to the two most common natural cellulose fibres
cotton and linen. The unique properties of cornhusk fibres such as good pliability, moderate strength,
durability, high elongation, and high moisture regain would provide unique properties to products
made from corn fibres. The several benefits possible to agriculture, industrial materials, energy and
the environment by using corn fibres are expected to make these fibres preferable over the currently
available natural and man-made fibres [32].
The most active current area of research in natural polymers involves the polyhydroxyalkanoate
(PHA) esters (alkanoates). These polymers were found to be produced by fluorescent
Pseudomonads and other bacteria which generate and store them as reserves of carbon and energy.
Their production has now been achieved in transgenic (genetically engineered) plants. In addition to
their being biosynthesized without the need of petroleum-based monomers, the ‘Green’ alkanoates
reflect their biological origins in being completely biodegradable [11].
Polycaprolactone (I) is a synthetic polymer prepared by ring opening polymerisation of caprolactone. It
is similar to PHAs and fully biodegradable, but degrades at a lower rate compared to PHAs. Due to
lower melting temperature of about 60 °C, the polymer is mainly used in polymer blend or as a matrix
for biodegradable composites. Electrospinning may play a role in the spread of biodegradable fibres,
especially for application in nonwoven biodegradable textiles [33].
The Electrospinning relies on organic solvents for the dissolution of polymeric materials, but most
biopolymers, however, are insoluble in organic solvents so they cannot be electrospun using
conventional approaches. Non-volatile room temperature ionic liquids (RTILs) can provide a ‘greener’
7
O
O*
1. polycaprolactone
*
processing alternative by preventing the release of harmful volatile compounds to the environment
[34].
Recycled Textiles
Much of the painfully achieved textile products are thrown away, buried or burned releasing ozone-
releasing methane gases after use. When the fibres cannot burn thoroughly, air-born particulates are
released due to incomplete decomposition of the material causing asthma.
The textiles being nearly 100% recyclable, nothing in textile and apparel industry should be wasted.
The textile recycling industry is one of the oldest and most established recycling industries in the
world. Textile recycling materials may be pre-consumer or post consumer (i.e. used garments or
articles). The sorting categories of textile recycling by volume is represented by a pyramid structure,
the base of which consists of used cloth market (48%), followed by conversion to value added new
materials (29%), cut into wiping and polishing cloths (17%), landfill and incineration for energy (<7%).
The peak of the pyramid is represented by ‘Diamonds’ (1-2%) which have high value for antique
quality or for other reason [35].
Polyester fibre is one of the most non-biodegradable polymers which create environmental problems.
Major revolution happened in 1993 when Wellman Inc. introduced the first polyester textile fibre made
from post consumer PET packaging - Fortrel® and EcoSpun®. There are two broad types of recycled
polyester namely:
1) Simply melted and re-extruded into fibres and
2) A multi-stage de-polymerisation and re-polymerisation to produce better quality yarn.
However, re-cycled polyester yarn is not always as good as virgin polyester. Colour consistency is
difficult to achieve, particularly on pale shades [36].
If the carpet yarns are made of polypropylene and they’re held together with a polypropylene Licocene
back-coating, the product can be reused simply by melting [37].
Greener Dye and auxiliaries
The greener approaches are:
1) Elimination of harmful azo dyestuffs
2) Alternative synthesis for eco-friendly products.
3) Search for sustainable source such as natural dyes. They, in general, have poor to moderate light
fastness. It was found that the natural additives Vitamin C (ascorbic acid) and gallic acid (found in
stomach, tea leaves, oak bark and many other plants) were most effective in reducing the rate of
fading in madder, weld and woad dyed cotton [38].
4) Easy degradable dyes: Most of the synthetic dyes are not easily biodegradable and are extremely
difficult to remove during effluent treatment. The incorporation of the hydroxy group into the
structure of di-(tri) arylmethane dyes in ortho position to the central carbon will result in a very
easy and effective oxidation of the dye by dilute H 2O2 at moderate pH under strong catalytic effect
of chloride anion together with methyltrioxorhenium MeReO3 (MTO). This universal principle can
be used by synthetic chemists working on the design of future environmentally-friendly
polyarylmethane dyes. As all dyes of this type are synthetically produced, the effect of the ortho-
hydroxy group on the colouristic properties of the dye can be easily counterbalanced by the
choice of another appropriate substituent [39].
Biodegradable surfactants
By reacting dextrins with fatty acids and their derivatives, new sustainable and biodegradable
surfactants have been formed. They have highly desirable physical properties including low foaming,
good wetting and whitening ability, as well as excellent biodegradability [40].
Queste reported [41] that the researchers in France and Germany have jointly developed a new class
of so-called ‘solvosurfactants’ (which exhibit the properties of both solvent and surfactant and are
commonly used in applications such as coatings and degreasing, as well as perfumery and inks) that
are derived from glycerol, a renewable material from bio diesel.
Alkylphenolethoxylates (APEs) or APEO have been widely used for emulsification of hydrophobic
liquids or for dispersing of hydrophophic particles like pigments, resins or fats in water. Besides other
concerns, the biodegradation of nonylphenolethoxylates (NPE) forms NP(EO)1–3, a recalcitrant and
very fish toxic metabolite, whereas biodegradation of green alternatives like alkylpolyglycosides or
fatty alcohol ethoxylates follow a rapid and complete degradation mechanism leading to the
conclusion that polyglycosides and polyglycolethers of short, medium and long chain fatty alcohols
and their sulphates, phosphates or sulfosucinates form a complete base set of green surfactants [42].
Greener Preparatory Processes
Some greener preparatory processes are:
1) Purification of cellulose by extraction by carbon dioxide and ionic liquids,
2) High temperature water extraction of lignin,
8
3) Substitution of chlorine bleaching with non-polluting oxidant, hydrogen peroxide,
4) Carbon dioxide-based dry cleaning.
5) Elimination of ozone-depleting chemicals such as carbon tetrachloride (stain remover).
Photo bleaching
The cellulosic fabrics were bleached effectively by a selective photolysis of the coloured compounds
using various excimer lasers (KrF, XeCl, XeF), a low-pressure mercury lamp, and a black-light
fluorescent lamp in the presence of sodium peroxocarbonate (Na 2CO3·1.5H2O2) or mixtures of sodium
carbonate and hydrogen peroxide aqueous solutions at room temperature. The efficiency of the
photochemical bleaching was found to be comparable to that of the commercial thermal bleaching
processes when a XeF excimer laser or a black-light fluorescent lamp were used as light sources [43].
The experiment was also carried out in the presence of several reducing agents. Sodium borohydride
(NaBH4) gave the best bleaching efficiency [44].
Bio- processing
Bioscouring processes are more environmentally friendly and consume considerably less water than
alkaline scouring. Water absorbency and tenacity at maximum load and DP are similar, but the weight
loss and the whiteness of fabrics are greater in case of alkaline scouring. The ecological parameters
of remaining baths after scouring with alkaline pectinases (Bioprep 3000L from Novozymes) were low
enough to be directly drained into the sewage system. Alkaline peptinases have high ecological
parameters, but both enzymes are biodegradable [45].
Life cycle assessment was performed by M/s Novozymes at textile mills in China. bioscouring with
Scourzyme 301 L (containing a pectate lyase enzyme) saved a range of chemicals, water, steam and
electricity with consequent reduction of environmental impacts like global warming significantly [46].
A study [47] was made to develop a new process to desize, bleach, and dye starch-sized cotton
fabrics in one bath using enzymes. Desizing was performed with an amyloglucosidase/ pullanase
enzyme (Dextrozyme DX, manufactured by Novozymes) instead of a conventional amylase enzyme
for hydrolysis of starch. The advantages of the new one-bath process claimed are less auxiliary
demand, lower environmental impact, and energy and water savings compared to the conventional
desizing, scouring, bleaching, and dyeing sequence.
Nicholson and John [48] identified a series of the enzymes in the genomic sequence of Clostridium
perfringens, a bacterium known to reduce indigo, and suggested that at least one of these enzymes
might play a role in indigo reduction in denim production.
Greener dyeing processes
The following are some of the improvement for making existing dyeing processes greener:
1) Optimise processes to reduce process time and energy consumption.
2) Reduce consumption of water (ultra low liquor ratio dyeing - 3:1 to 4:1 for polyester and 6:1 for
cotton), electrical power, steam consumption in general,
3) Rapid dyeing techniques for polyester utilising optimised design of dyeing machines and suitable
dyes.
4) Optimise dye/chemical costs
5) Eliminate reprocessing and shade correction
6) Sulphur dyeing: substitution of hazardous sodium sulphide with sustainable, nontoxic,
biodegradable, cost-effective reducing sugars [49].
7) Reactive dyeing: The dyeing of cationic cotton is more sustainable because it requires no salt, no
alkali and it can be dyed at relatively low temperatures with reactive dyes. The proposed
cationising agent is 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHTAC) [50] or
copolymer of diallyldimethylammonium chloride and 3-aminoprop-1-ene and copolymer of 4-
vinylpyridine quaternised with 1-amino-2-chloroethane [51].
8) Right-First-Time dyeing: It is also termed as ‘no addition’ dyeing or ‘blind dyeing’. Elimination of
the inspection stage made a significant saving [5]. Twenty factors which must be monitored or
controlled to achieve RFT processing in the dyeing process have been identified [52].
Manufacturers have also helped by continual refinement of textile machine design and its control
equipment, which together with dye selection and reliable recipe prediction systems in the
laboratory have contributed to a high proportion of ‘right first time’ dyeing [5].
9) Multiple savings are possible through automation in textile dyeing and printing such as:
(a) Process control - 10-30% saving in water and energy as well as 5-15% saving in dyes and
chemicals.
(b) Auto-dispensing - 5-10% savings in dyes, pigments and chemicals.
(c) Computer-controlled weighing and stock-taking - 10-15% savings in dyes, pigments and
chemicals.
9
(d) Colour measurement and matching - significant improvement in quality and 30-40% savings
of dyes and pigments.
Some of the new greener coloration technologies with minimum environmental impact [5] are:
1) Attaining about 90% dye fixation on cellulosic fibres by batchwise dyeing using poly-functional
reactive dyes.
2) A reawakened interest in cold pad–batch dyeing processes using reactive dyes.
3) More than halving the energy, water and chemical consumption in the continuous dyeing
methods.
4) In chemical-free denim processing [53] laser technology is used to burn away the surface of the
dyed denim fabric or a pair of jeans on a mannequin to replicate an authentic worn look. The laser
system is very quick and a pair of jeans can take as little as 15 seconds to process.
5) Digital printing is certainly a sustainable technology – it uses far less water and produces far less
waste than traditional methods.
6) Cooltrans cold transfer printing process in which reactive dyes are transferred from printed paper
and fixed at room temperature using cold batching method on pretreated cotton, viscose, linen
and silk [54].
7) Supercritical carbon dioxide dyeing.
Supercritical Carbon Dioxide (scCO2) Dyeing
A supercritical fluid is one that has characteristics of both liquid and gas and consists of a substance
above its supercritical temperature and pressure (31.1 °C and 73.8 atm respectively, for CO2 as
shown in Figure 1).The supercritical fluids can adopt properties midway between a gas and a liquid
expanding to fill its container like a gas but with a density like that of a liquid. Such solvents have not
yet been implemented in textile industry, but their use as dyeing medium (called waterless dyeing)
has received considerable attention from researchers in the past two decades, as is illustrated by the
143 articles mentioned in the review by Bach et al. [55]. The most widely used supercritical fluid is
carbon dioxide (scCO2), because it combines a relatively mild critical point with non-flammability, non-
toxicity and a low price. Because of its green and safe character, it is the best supercritical solvent for
textile dyeing. The CO2 is a waste product of combustion, fermentation and ammonia synthesis, so
that no CO2 has to be produced especially for dyeing.
The carbon dioxide and the residual dye (after dyeing) can be easily separated by depressurisation
and both compounds can be recycled. No waste is generated. The energy-intensive drying after
dyeing is not required. As scCO2 is a non-polar solvent, no dispersing agent is needed when polyester
is dyed. As the process operates at
conditions of typically 120ºC and
300 bar, high-pressure equipment is
needed which results in high
investment costs. The supercritical
dyeing process was investigated
[56] experimentally for both reactive
and non-reactive dyeing.
An outstanding dye fixation of 99%
on cotton dyed in supercritical
carbon dioxide was achieved using
monofluorotriazine reactive dyes
and by adding small quantities of
acids. A rinse step of the cotton
after dyeing is not necessary to
remove unfixed dye [57]. However,
water-soluble dyes are insufficiently
soluble in scCO2. The dyeing is,
therefore limited to synthetic fibres
using scCO2 soluble disperse dyes.
A pilot plant was set up in the field
of supercritical dyeing of PET
textiles. Experimental results
showed that equilibrium partition is more favourable to the fibre than the supercritical bath and
increases at high temperatures and low densities range. The choice of the proper working conditions
is a compromise between a high value of the partition coefficient and an acceptable level of the dye
solubility in the dyeing bath, to guarantee a rapid and uniformly dyed product [58].
10
Fig. 1 Various Physical States of Carbon Dioxide
A two-step process (treatment with supercritical CO2 followed by treatment with liquid CO2) was
proposed for cleaning of old silk textiles. The fibres and the textile structure were not physically
damaged [59].
Greener After-treatments
An environmentally friendly method for improvement of the colour fastness to washing and rubbing is
the layer by-layer (up to 30 layers) deposition of polyelectrolytes multilayers (PEM) on dyed silk fibres.
Successive deposition of cationic poly(diallyldimethylammonium chloride) and anionic poly(sodium 4-
styrene sulphonate act as an electrostatic barrier and is more efficient than single polymer in
preventing the dye diffusion [60].
Greener Finishing Agents
The most widely used crosslinking agents in DP finishes, N-methylol agents or N-methylolamides fall
in the category of formaldehyde reactants [61]. The release of formaldehyde vapours is a problem
with those agents. It depends on the reactant types, the catalyst types, the condition of the treated
fabrics, and the additives in the impregnating bath and most importantly the time and temperature of
cure [62].
The Occupational Safety and Health Administration (OSHA) have set the upper limit for formaldehyde
in air at 0.75 parts per million average over an eight-hour work shift [63]. Formaldehyde is a
carcinogen to animals [62]. Some formaldehyde-free DP finishes are:
1) Cyclic addition of glyoxal with NN/dimethyl urea, namely DHDMI (1,3 dimethyl-4,5-
dihydroxyethyleneurea)
2) Polycarboxylic acids (PCA) - their main drawback is loss of tensile strength due to acid-catalysed
cellulose chain cleavage. The most important PCA reactants are
butanetetracarboxylic acid (BTCA) and citric acid (CA) [64]. BTCA, in the presence of sodium
hypophosphite, provides the same level of durable press performance as conventional DMDHEU
reactant, but it is quite costly [63].
Nano Finish
Nanotechnology offers large specific areas which facilitate a high level of functionality and is highly
compatible with textiles, which also have high specific surface. Aftercare of textiles on both domestic
and industrial scales (such as hotel laundry) has a major negative environmental impact in the textile
life cycle. The impact of durable surface coating could be highly significant. Nano surface finishes may
render textile and clothing stain resistant, abrasion resistant, water and oil repellent, self-cleaning,
antistatic or antibacterial with consequent prolonged useful life of textile materials and minimise the
need for washing or dry cleaning. Certain treatments may reduce the need for ironing with consequent
saving of energy and water.
NanoSphere fabric finish, based on lotus effect developed jointly by Clariant and Swish chemicals,
repels liquids and other viscous food substances. It is based on C6 fluorochemicals and awarded the
bluesign mark for environmental safety. The companies like Silverton, SmartSilver and X-Static
claimed to bond a layer of silver permanently outside of a nylon core claiming improvement in
antimicrobial property and electrical conductivity. A similar finish is developed for cotton based on
polyhexamethylene bignanide (PHMB) with a marketing slogan ‘Stays fresh, wash less’. Silver is non-
toxic to humans at normal molecular scale, but it is toxic to bacteria and micro-organisms at the nano-
scale – destroy cell membrane of bacteria, deactivate metabolism and prevent cell growth. Hence, the
claim that nano silver-based products are totally safe is questionable. Extremely small nanoparticles
may move easily through cell membranes of the body thereby gives rise to serious concern for human
and animal health.
Compared with conventional flame retardants, nanocomposites offer significant advantages as flame
retardant. Only very low concentrations of silicate are necessary in nanocomposites, resulting in low
density, lower cost and ease of preparation. The materials are more eco-friendly as the treatment
adds no halogens, phosphates or aromatics. They do not produce increased carbon monoxide and
soot during combustion.
An interesting development in the field of flame retardancy is the use of polymer nanocomposites as a
substitute of toxic brominated flame retardants (BFR). Nanocomposites may be described as two-
phase materials, consisting of a dispersion of appropriate filler (on a nanometre scale) through a
polymer matrix. Dispersion of 2-5% nanoclay in the polymer matrix significantly improves the
mechanical, thermal, barrier and flame-retardant properties of base polymer. Layered silicates in bulk
polymer form a protective barrier when exposed to heat. The barrier slows fuel pyrolysis and also
reduces the flame temperature. However, the fibres have high surface area and fuel-rich surface.
Nanocomposites by themselves, therefore, only lower the heat release rate and the presence of
nanoclay alone can not make polymer self-extinguishable. The polymer nanocomposite can be used
11
in combination with reduced quantities of conventional flame retardants
(www.eupen.com/highlights/publications.html).
Surface Coating and Treatments
After application of water-based finishes, the textile materials need energy intensive drying process to
remove water and therefore environmentally harmful and expensive. In plasma treatment, dry
treatment is carried out by excited gas phase with negligible consumption of water and low
consumption of energy. The treatment may be utilized for surface cleaning, ablation or etching,
grafting, polymerization of the most external layer of the substrate.
In principle, plasma treatment can be carried on all polymeric and natural fibres for the following
purposes:
1) Desizing,
2) Change in wettability (to make fibres hydrophilic or hydrophobic),
3) Improvement of affinity and levelling properties of dyes,
4) Wool degreasing.
5) Anti-felting finish of wool,
6) Sterilisation of textile materials.
The surfaces of various lignocellulosic fibres were modified using AAPP. Prolonged exposure to
atmospheric air pressure plasma (AAPP) causes the hydrophilic behaviour of abaca, flax and sisal
fibres to increase. The exception is the hemp fibre [65]. In terms of sustainability, there is little doubt
that atmospheric pressure plasmas stand on the threshold of a revolution in textile processing as
great as that delivered by wet- and heat-based processing in times long past. Moreover, it is a dry and
eco-friendly technique, avoiding waste production as found in wet-chemical processes. However, for
the transfer into industry, both the feasibility of scale-up and economic aspects have to be regarded.
Green Composites
Environment-friendly, fully biodegradable, ‘green’ composites based on plant based fibres and resins
are increasingly being developed for various applications as replacements for the prevailing non-
biodegradable materials derived from petroleum. Unlike petroleum, plant based proteins, starches and
fibres are yearly renewable. Moreover these green composites may be easily composted after their
life, completing nature’s carbon cycle. Flax yarn reinforced cross-linked soy flour (CSF) composites
are fully biodegradable, environment friendly green composites which can be used in secondary and,
in some cases, primary structures in indoor applications [66].
Preparation of cellulose composites using ionic liquids, such as 1-butyl-3-methylimidazolium chloride
(BMIMCl) and 1-allyl-3-methylimidazolium chloride (AMIMCl), has broadened the conventional
cellulose application scope. It can reduce society’s dependence on nonrenewable petroleum-based
synthetic polymers [67].
Effluent Treatment
Hydrogen peroxide and oxygen can safely and powerfully destroy many pollutants, but in nature the
process usually requires an enzyme, peroxidase, that vastly increases the rate of the reaction. The
investigators at Carnegie Mellon University’s Institute for Green Oxidation Chemistry have developed
a group of designer catalyst molecules called TAML (tetraamido macrocyclic ligand) activators that
work with hydrogen peroxide and other oxidants to break down a wide variety of stubborn pollutants.
TAMLs accomplish this task by imitating the enzymes in our bodies that have evolved over time to
combat toxic compounds. Synthetic TAMLs peroxide-activator (with iron as the central metal atom)
decomposes peroxide on timescales ranging from minutes to hours. The molecular weight of a TAML
is about 500 daltons (a dalton is equal to one twelfth the mass of carbon 12), whereas the weight of
horse-radish peroxidase, a relatively small enzyme, is about 40,000 daltons. The diminutive TAML
activators are easier and cheaper to make, and much more versatile in their reactivity, than their
natural counterparts [68].
A study demonstrates a good potentiality of peroxidase towards the treatment of halogenated
phenolic compound in presence of an additive [69]. The removal of coloured aromatic compounds
from wastewater by peroxidases is now well-known. Peroxidase from fenugreek (Trigonella foenum-
graecum) (FSP) seeds is highly effective in the decolorization of textile effluent. FSP can be
effectively employed for the decolorisation of textile effluent in the presence of various redox
mediators. The treatment of effluent by FSP in the presence of redox mediator, 1-hydroxybenzotrizole
(HOBT), produced insoluble aggregates which could be easily removed by centrifugation. Thus, the
peroxidase from fenugreek seeds has shown its potential in the remediation of hazardous aromatic
pollutants [70]. Peroxidase adsorbed on a cost free support, fly ash, was very effective and stable for
the oxidative polymerization and removal of highly toxic compound and an endocrine disruptor,
bisphenol A [71].
Coagulant
12
The chemical coagulation by alum and polyaluminium chloride (PAC) is a method of choice for
treating waste waters before being fed to the biological treatment unit. Besides the possibility of
Alzheimer’s disease due to aluminium, the long-term effects of these chemicals on human health are
not known. To minimize these drawbacks, biodegradable natural polyelectrolytes [72], which are
extracted from plant or animal life can be workable alternatives to synthetic polyelectrolytes. Naturally
occurring Cassia angustifolia (CA) seed gum was evaluated against the chemical coagulant
polyaluminium chloride (PAC) for its coagulation ability to remove colour from synthetic dye solutions.
Cassia seed gum can be an effective coagulant aid for direct and acid dyes. It can act as a working
substitute, partially or fully, for synthetic chemical coagulants such as PAC [73].
Adsorbents
The biosorption is more efficient for the retention of cations or organic compounds at trace
concentrations in aqueous solutions than the conventional treatment, involving also low energetic
consumptions. Cationised cotton is sometimes used for the removal of anionic dyes from aqueous
effluent produced by the textile industry as it is natural, inexpensive and renewable [74]. Although the
sorption capacity of the sawdust is not very large, experimental results provide promising perspective
for the utilization of sawdust as bio-sorbent in reducing pollution of textile effluents [75].
The capacity of using cellolignine, sawdust, pumpkin core, hemp fibres and peat as biosorbents for
reactive dyes, Fe (II), Cu (II) and Cr (III) ions from aqueous solutions was studied [76].
Lignin, the third important component of plant biomass (16% to 33%) after celluloses and
hemicelluloses, is an inexpensive natural material, available as a by-product from the paper and pulp
industry (50 million tonnes per year) [77]. The removal of some pollutant species by sorbents based
on lignin, modified lignin and/or lignocellulosic materials has been intensively studied; the results
suggested that sorption on lignin is a progression towards a perspective method [78].
Ash is a residue that results from the combustion of coal in power plants. Easily and abundantly
available ash is a strong choice for economic means of removal of dyes. The coal ash in form of
adsorbent could be disposed off safely by burning after drying [79].
Eco-label
Eco-labels have emerged as a primary tool in marketing to more well-informed and ‘green’
consumers. According to Global Ecolabelling Network, an ecolabel is ‘a label which identifies overall
environmental preference of a product within a product category based on life cycle consideration’.
This label is awarded by an impartial third party to products that meet established environmental
leadership criteria. Such labels are voluntary declarations and are a clean attempt to set new
‘standard’ for labelled textile products. These aim at developing market with greater environmental
protection fulfilling consumer expectation towards reducing environmental and social impacts. Eco-
labels are very important to the development of a sustainable and a credible textile industry.
Examples of a few eco-labels are Oeko-Tex Standard 100 (www.oeko-tex.com ) and Global Organic
Textile Standard (GOTS, www.global–standard.org) used globally, Blue Angel (Germany), Green Seal
(USA), Eco-mark (Japan) etc.
Eco-legislation
REACH (www.fibre2fashion.com) is a new European Community Regulation on chemicals and their
safe use. It is a new regulatory framework proposed by the EC on October 29, 2003. It is a single,
coherent system for new and existing chemicals with the following three new elements:
1. Registration (30,000 substances traded in EU; 100,000 on EINECS)
2. Evaluation (5,000 substances)
3. Authorisation (1,350 substances)
CHemical Substances
Conclusion and Future Trends
What will the chemical industry of the near and far 21st century look like? The application of the
principles of green chemistry and other aspects of clean technology will increasingly lead to more
environmentally compatible manufacturing systems. “Just-in-time” manufacturing can ease
transportation and storage problems with small, intensive plants replacing the giants of the 20th
century. Looking further ahead, we can expect to see more chemical plants taking advantage of local
resources including plant-based feedstocks, clay-based reagents, and catalysts, etc., and it is quite
possible, as transport becomes a bigger issues, that manufacturing will be largely in response to
regional needs rather than global market opportunities.
The 21st century philosophy for textile dyeing is follows:
• Minimum human/operator intervention,
• Process steps optimised for utility consumption,
• Decisions made strategically not on a daily routine basis,
13
• Processes devised and selected to produce the correct shade and quality as an expectation not
just an intention,
• Digital shade passing and colour communication,
• Profits are made by doing it right - not just by doing it cheaply [80].
A systematic approach can ensure effective application. Systematic eco-plan can lead business to
such an extent that by 2012 it should:
• Become carbon neutral,
• Send no waste to landfill,
• Develop sustainable sourcing routes,
• Set new standards in ethical trading,
• Help customers and employees to live a healthier lifestyle.
Carbon neutrality’, or having a ‘net zero carbon footprint’, refers to achieving net zero carbon
emissions by balancing a measured amount of carbon released with an equivalent amount
sequestered or offset [81].
References
1) T J Collins and C Walters, Scientific American, March (2006) 84-90.
2) S K Sikdar, Clean Techn. Environ Policy (2007) 9:167–174, DOI 10.1007/s10098-007-
0087-6.
3) National Research Council, Sustainability in the Chemical Industry: Grand Challenges
and Research Needs— a Workshop Report. (Washington, DC: National Academies Press, 2005).
4) M P Wilson and M R Schwarzman, Environmental Health Perspectives, 117 (2009) no. 8,
1202-1209.
5) T.L. Dawson, Coloration Tech., 124 (2008) 67-78.
6) J Clark and D Macquarrie (Ed), Handbook of Green chemistry and technology, Ltd,
(Oxford: Blackwell Science, 2002).
7) A B Koltuniewicz and E Drioli, Membranes in Clean Technologies. Theory and Practice,
(Weinheim, Germany: WILEY-VCH, 2008).
8) J, Michael Fitzpafrick, Polymer News, 29 (5) (2004) 138-146.
9) M Kidwai, Pure Appl. Chem., 73 (8) (2001) 1261–1263.
10) G J Hutchings, Green Chemistry has a Golden Future, Europacat7, Cardiff University,
UK), August (2005).
11) S E Manahan, Fundamentals of Environmental Chemistry, (Boca Raton: CRC Press LLC,
2001).
12) R Höfer, D Feustel and M Fies, Welt der Farben, 1997, II
13) M Ash and I Ash, The Index of Solvents, (Brookfield, VT, USA: Gower Publishing Limited,
1996).
14) P Tundo, A Perosa and F Zecchini (Edited by), Methods and Reagents for Green
Chemistry: an Introduction, (New Jersey, USA: John Wiley & Sons, 2007).
15) Ionic Liquids in Synthesis, (Edited by) P. Wasserscheid and T. Welton, Weinheim: Wiley-
VCH, 2003).
16) Mahdi M. Abu-Omar, "Green chemistry", in AccessScience@McGraw-Hill,
http://www.accessscience.com, DOI 10.1036/1097-8542.YB020405.
17) W Wardencki, J Cury, J Namieśnik, Polish Journal of Environmental Studies, 14 (4)
(2005) 389-395.
18) R Mestres, Green Chemistry, (2004) G10-G12.
19) B M Trost, Angew. Chem. Int. Ed. Engl, 34 (1995) 259 – 281.
20) R Sheldon, Chemtech, 24(3) (1994) 38 – 47.
21) Chao-Jun Li, Canadian Chemical News, April, 2004.
22) M Poliakoff and P Licence, Nature, 450 (6) December (2007).
23) R. A. Sheldon, (2005). Green Chem., 7 (2005) 267.
24) A Sherburne in Sustainable textiles: life cycle and environmental impact, (Oxford, UK:
Woodhead, 2009), 3-32.
25) L Grose in Sustainable textiles: life cycle and environmental impact, (Oxford, UK:
Woodhead, 2009), 33-60.
26) W Albrecht, M Reintjes and B Wulfhorst, Chem. Fibers Int., 47 (1997) 298.
27) P White, M Hayhurst, J Taylor and A Slater, Biodegradable and Sustainable Fibres.
(Edited by) R S Blackburn (Cambridge: Woodhead, 2005), 157.
28) K Anderson, Ionic Liquids: An Environmentally Friendly Alternative, 02/12/2010,
www.techexchange.com.
14
29) I R Hardin, S S Wilson, R Dhandapani, V Dhende, presented at AATCC International
conference on March 2009, AATCC Review, October 2009, 33-36.
30) M. Merrill, K Parent, M Kirchhoff, Chem Matters, April, 7, 2003.
31) R W McCabe and A Taylor, Green Chem., 6 (2004) 151–155, DOI: 10.1039/b400372c).
32) N Reddy and Y Yang, Green Chem., 7 (2005) 7, 190–195. doi:10.1039/B415102J).
33) I Chodak and R S Blackburn in Sustainable textiles: life cycle and environmental impact,
(Oxford, UK: Woodhead, 2009), 88-112.
34) L Meli, J Miao, J S Dordick and R J Linhardt, Green Chem., 12 (2010) 1883-1892.
35) J M Hawley, Textile recycling: A system perspective, in Recycling in Textiles, (Edited by)
Y Yong (Cambridge: Woodhead), (2006).
36) Dyeing Recycled Pet, www.ecotextile.com.
37) Walking the talk: Clariant products provide ‘green’ chemistry successes, News Release,
www.clariant.com, August 19 (2008).
38) D Cristea and G Vilarem, Dyes and Pigments, 71 (2006) 39.
39) A U Moozyckine and D M Davies, Green Chemistry, 4 (2002) 452–458.
40) H J Wang and K M Chen, J. Applied Polymer Science, 98 (2005) 711.
41) S. Queste et al., Green Chem., 8 (2006) 822.
42) R Höfer and J Bigorra, Green Chem., 9 (2007) 203–212. DOI: 10.1039/b606377b.
43) A Ouchi, H Sakai, T Oishi, T Hayashi, W Ando and J Ito,, Green Chemistry, 5 (2003)
516–523. DOI: 10.1039/b304680j
44) A Ouchi, T Obata, T Oishi, H Sakai, T Hayashi, W Ando and J Ito, Green Chemistry, 6
(2004) 198–205. DOI: 10.1039/b315580c
45) P Preša and P F Tavčer, Textile Research Journal, 79(1) (2009) 76–88. DOI:
10.1177/0040517508092019.
46) P H Nielsen, H Kuilderd, W Zhou and X Lu in Sustainable textiles: life cycle and
environmental impact, (Oxford, UK: Woodhead, 2009) 113-138.
47) H A Eren, P Anis and A Davulcu, Textile Research Journal, 79 (12) (2009) 1091–1098.
DOI: 10.1177/0040517508099388)
48) S K Nicholson and P John, Appl. Microbiol. Biotechnol., 68 (2005) 117.
49) R S. Blackburn, S M. Burkinshaw, Journal of Applied Polymer Science, 89 (2003) 1026–
1031.
50) M Hashem, P Hauser and B Smith, Text. Res. J., 73, 762 (2003).
51) R S. Blackburn, S M. Burkinshaw, Journal of Applied Polymer Science, Vol. 89 (2003)
1026–1031.
52) J Park and J Shore, Practical Dyeing (Bradford: SDC, 2004)
53) Chemical-free denim processing, www.ecotextile.com
54) M R Thiry. AATCC Review 10 (3) (2010) 32-39.
55) S E Manahan, Fundamentals of Environmental Chemistry, (Boca Raton: CRC Press LLC,
2001).
56) R Höfer, D Feustel and M Fies, Welt der Farben, 1997, II
57) M V Fernandez Cid, J van Spronsen, M van der Kraan, W J T Veugelers, G F Woerleeb
and G J Witkamp, Green Chem., 7 (2005) 609–616.
58) M Banchero, S Sicardi, A Ferri, and L Manna, Textile Research Journal, 78(3) (2008)
217-223. DOI: 10.1177/0040517507081297).
59) M Sousa, M J Melo, T Casimiro and A Aguiar-Ricardo, Green Chem., 9 (2007) 943–947,
doi:10.1039/B617543K).
60) S T Dubas, E Chutchawalkulchai, S Egkasit, C Iamsamai and S Potiyaraj, Textile
Research Journal., 77(6) (2007) 437–441. DOI: 10.1177/0040517507071969).
61) H Peterson, Rev. Prog. Col., 17 (1987) 7-22.
62) T. F. Cooke & H. D. Weigmann, Textile Chemist and Colorist, 14 (1982) 100-106 and
136-144
63) B A K Andrews, Textile Chemist and Colorist, 22 (1990) 63-67.
64) C. M.Welch, Textile Research Journal, 58 (1988) 480-486.
65) A Baltazar-Y-Jimenez and A Bismarck, Green Chem., 9 (2007) 1057–1066.
doi:10.1039/B618398K.
66) S Chabba, G F Matthews and A N Netravali, Green Chem., 7 (2005), 576–581.
67) S Zhu, Y Wu, Q Chen, Z Yu, C Wang, S Jin, Y Ding and G Wu, Green Chem., 8, (2006)
325–327.
68) T J Collins and C Walters, Scientific American, March, 2006, 84-90.
69) H Ashraf, Q Husain, Desalination, 262 (2010) 267–272.
15
70) Q Husain, Z Karim and Z Z Banday, Water Air Soil Pollution 212 (2010) 319–328).
71) Z Karim, Q Husain, Food and Chemical Toxicology (Elsevier), 48 (2010) 3385–3390).
72) R Sanghi, Asian Textile J. , 10(3) (2001) 73–75.
73) R Sanghi, B Bhatttacharya and V Singh, Green Chemistry, 4 (2002) 252–254.
74) A P Abbott, T J Bell, S Handa and B Stoddart, Green Chem., 8 (2006) 784–786.
75) D Suteu, D Bilba, C Zaharia, A Popescu, Scientific Study & Research, IX (3) (2008).
ISSN 1582-540X, p293-302.
76) D Suteu, I Volf, M Macoveanu, Environmental Engineering and Management Journal, 5
(2) (2006) 119-134.
77) D Suteu, T Malutan and Doina Bilba, Desalination, 255 (2010) 84–90.
78) X Guo, X Shan, S Zhang, Journal of Hazardous Materials, 151 (2008) 134–142.
79) D Suteu, Sorption of Dye from Aqueous Solution onto Lime-Coal Ash Sorbent,
International Scientific Conference at Gabrovo on 23 – 24 November 2007.
80) A C Welham, www.dyehousedoctor.com, Textile Dyeing in the Age of Aquarius.
81) Mark Sumner, Plan A & Eco Dyehouses, Part I, (Bradford: Society of Dyers and
Colourists, 2009).
16
Chapter
Investigation on removal of C.I. Disperse Orange‐25 was performed by commercial microcrystalline cellulose after modification with aminopropyltriethoxysilane to enhance the adsorption capacity. Initial dye concentration, pH, sorbent dosage, contact time and temperature were the parameters, which were followed to decide the impact in batch adsorption method. Characterization study was done using scanning electron microscope, infrared spectrometer investigation, nitrogen‐adsorption surface zone. The outcomes demonstrated that the adsorption was positive at acidic pH and reduction in COD. Rise in contact time, sorbent dosage, and decline with initial dye concentration and temperature of the medium had a positive impact on dye removal. Sorption balance was proposed by 2‐parameter (Langmuir, Freundlich) and 3‐parameter (Redlich‐Peterson) conditions, and it was found that Langmuir isotherm fitted well the adsorption data with the most elevated correlation (R 2 ≥0.99). The Gibb's free energy, change in enthalpy and entropy were the thermodynamic parameters, which were evaluated during adsorption process and the results clearly suggested the endo‐dermic nature of the process. Furthermore, the results revealed that modified sorbent proved to be effective and low‐priced sorbent.
ResearchGate has not been able to resolve any references for this publication.