Author: Zahid Sarwar
Supervisor: Dr. Munir Ashraf
A large quantity of water is consumed by textile units for manufacturing of end products. Textile processing industries though consume major portion as each step involves large consumption of water like desizing has to be followed by intensive washing with water to remove impurities and sizing agents. Scouring and bleaching also require intensive washes as well as hazardous chemicals are used for these treatments. Dyeing also require large amount of water especially in washing off. There are about 10,000 commercial available dyestuffs and 7×105 tones of dyestuff are being produced per annum in the world. The effluent of textile contains other toxic chemicals as well as these dyestuffs. The dyes are normally non-biodegradable and some are toxic as well.
Textile industry is the most water consuming and effluent producing industry. About 200 L of water is used to produce 1 kg of textile. The annual generation of waste water in Pakistani industries is 1.37 BCM. Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, color, acidity, and other soluble substances etc. Among the different types of dyes used in textile industries,60–70% are azo compounds. These dyes create severe environmental pollution problems by releasing toxic and potential carcinogenic substances into the aqueous phase.
Why to Treat Effluent:
The effluent should be treated before discharging due to its toxic nature and environmental concerns. Water is a natural source and preserving of natural resources is the need of the hour. The effluent when treated becomes less toxic and even non-toxic by various techniques. The overall benefits of the decolonization of textile industrial wastewater may include saving a huge amount of water, because textile industries are regarded as chemical intensive and water intensive. The treated water may be recycled in the same factory or reused in other applications such as other industries or agriculture that require a less quality water. This is considered to be very excellent means for saving huge amounts of water, especially, in the countries which are suffered with water deficiency.
Different Techniques for Effluent Treatment:
There are different chemical and physical methods available for color removal from water like
Why to Go With Nanotechnology:
Currently available treatment technologies either concentrate the pollutants by transferring them to other phases like coagulation and adsorption or involve high operating costs like sedimentation, filtration, chemical and membrane technologies with still the risk of generation of secondary toxic pollutants into the environment.Nano technology is the field of science focused on design, synthesis, characterization and application of materials on nano scale. This results in materials and systems that exhibit novel properties due to their size and broad applications.
The word Photocatalysis is from Greek origin and compose of two parts; Photo is derived from phos which means “light” and catalysis is derived from katalyo which means to “break apart” or “decompose”. As a whole photocatalysis means a chemical reaction in which a catalyst is activated by photons of light energy to modify the rate of chemical reaction without being consumed itself in that reaction. Photocatalyst is a material that is capable of absorbing light, producing electron–hole pairs that enable chemical transformations of the reaction participants and regenerate its chemical composition after each cycle of such interactions . Most common photocatalyst are transition metal oxides and semiconductors.