Industrial Water Footprint: Case Study on Textile Industries
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10.3 Scouring
Scouring is a chemical washing process carried out on the cotton fabric to remove
natural wax and nonfibrous impurities. Naturally occurring impurities such as noncellulosic components, wax, as well as added impurities such as dirt that are present
in the fiber and fabrics, are removed by this process. Scouring is performed in the
iron vessels called kiers where the fabric is enclosed and boiled in an alkali solution
of sodium hydroxide which forms a soap with free fatty acids. An excess amount
of water is then used to wash off these impurities from the surface of the fabric.
This method improves the absorptive capacity of the fabric material which enhances
the dyeing process that comes in the consecutive steps. Also, this process whitens
the color of the material without damage to the fiber structure. The effluent water
from this process consists of detergents, pectin, oil, and solvents from various other
processes.
10.4 Bleaching
Madhav et al. [23]. Bleaching is generally employed in both batch and continuous
modes of operation. The degree of bleaching is determined by the required level of
whiteness and absorbency.
10.5 Mercerising
Mercerization makes the fabric more lustrous and its tensile strength and dye uptake
capacity. It also reduces the shrinkage of fabric and gives a silk-like texture. This
process is carried out by submerging the cotton fabric in a medium of sodium
hydroxide (15–25%). It results in the phenomenon of swelling due to the absorption
of sodium hydroxide by the cotton fiber. After swelling, the basic solution used is
washed off thoroughly either by using an acid solution or water itself. During this
process, the fabric is subjected to vertical deformation which is prevented by applying
tension on both ends of the fabric material. Sodium hydroxide used in this process
is recovered in most of the industries by membrane assisted technologies.
10.6 Dyeing
Dyeing is the final process where the absorbent fiber responds readily to the coloration
of the final textile product. Colorants are added in the industry to impart color to the
cotton fabric material. Dyes are colorants that have a natural affinity towards the
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10.3 Scouring
Scouring is a chemical washing process carried out on the cotton fabric to remove
natural wax and nonfibrous impurities. Naturally occurring impurities such as noncellulosic components, wax, as well as added impurities such as dirt that are present
in the fiber and fabrics, are removed by this process. Scouring is performed in the
iron vessels called kiers where the fabric is enclosed and boiled in an alkali solution
of sodium hydroxide which forms a soap with free fatty acids. An excess amount
of water is then used to wash off these impurities from the surface of the fabric.
This method improves the absorptive capacity of the fabric material which enhances
the dyeing process that comes in the consecutive steps. Also, this process whitens
the color of the material without damage to the fiber structure. The effluent water
from this process consists of detergents, pectin, oil, and solvents from various other
processes.
10.4 Bleaching
Madhav et al. [23]. Bleaching is generally employed in both batch and continuous
modes of operation. The degree of bleaching is determined by the required level of
whiteness and absorbency.
10.5 Mercerising
Mercerization makes the fabric more lustrous and its tensile strength and dye uptake
capacity. It also reduces the shrinkage of fabric and gives a silk-like texture. This
process is carried out by submerging the cotton fabric in a medium of sodium
hydroxide (15–25%). It results in the phenomenon of swelling due to the absorption
of sodium hydroxide by the cotton fiber. After swelling, the basic solution used is
washed off thoroughly either by using an acid solution or water itself. During this
process, the fabric is subjected to vertical deformation which is prevented by applying
tension on both ends of the fabric material. Sodium hydroxide used in this process
is recovered in most of the industries by membrane assisted technologies.
10.6 Dyeing
Dyeing is the final process where the absorbent fiber responds readily to the coloration
of the final textile product. Colorants are added in the industry to impart color to the
cotton fabric material. Dyes are colorants that have a natural affinity towards the