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Dyeing wastewater and its treatment

2025-01-10

Production of printing and dyeing wastewater
Printing and dyeing wastewater mainly comes from the production process of printing and dyeing plants. In the process of printing and dyeing, a large number of dyes, auxiliaries and high concentration salts and other chemicals need to be used. These chemicals will be dissolved in water during the production process to form wastewater. In addition, the printing and dyeing process will also produce a large number of textile waste and solid waste, which will also become an important part of wastewater after treatment.
Characteristics and hazards of printing and dyeing wastewater
Printing and dyeing wastewater has the characteristics of large amount of water, high content of organic pollutants, large alkalinity and large changes in water quality, which is one of the industrial wastewater that is difficult to treat. The wastewater contains dyes, size, additives, oil agents, acids and bases, fiber impurities, sand substances, inorganic salts, etc. Printing and dyeing wastewater contains unreacted dyes, pigments (coatings), with heavy color, unreacted auxiliaries, as well as the products after reaction and the shedding on the fabric. More serious are carcinogenic and teratogenic organic compounds, toxic heavy metals and so on. The composition and properties of various components in wastewater vary irregularly with market changes, seasonal changes and supply changes.
Printing and dyeing wastewater not only pollutes the environment, but also destroys the ecosystem. If discharged directly without treatment, it will pollute rivers, lakes and other water bodies and affect the survival of aquatic organisms. At the same time, harmful substances in printing and dyeing wastewater may also enter the human body through the food chain, posing a threat to human health.
Principle and advantages of treating printing and dyeing wastewater with polymeric ferric sulfate
Polyferric sulfate (PFS) is an efficient inorganic polymer coagulant. The principle of its treatment of printing and dyeing wastewater mainly includes coagulation, adsorption and precipitation.
Coagulation: after hydrolysis of polyferric sulfate in water, a large number of positively charged iron ions (Fe ³ +) will be produced. These iron ions can neutralize with negatively charged colloidal particles, suspended solids and partially dissolved organic matter in wastewater to form large flocs.
Adsorption: polyferric sulfate has strong adsorption capacity due to its high polymerization, which can adsorb small particles of pigment, organic matter and other pollutants in wastewater.
Sedimentation: the formed flocs settle rapidly under the action of gravity, so as to realize the removal of pollutants in wastewater.
The advantages of polymeric ferric sulfate in treating printing and dyeing wastewater include:
Efficient decolorization: polymeric ferric sulfate has good removal effect on pigment in printing and dyeing wastewater. Its enhanced flocculation can adsorb and bridge the small pigment particles in the water, and sweep them, so as to achieve a high degree of decolorization effect. At the same time, the iron ions carried by PFS dissolved in water also have a certain reduction effect on the pigment in water.
Organics removal: PFS can also remove some organics in wastewater, especially those that precipitate with iron ions.
Significant phosphorus removal effect: printing and dyeing wastewater usually contains high phosphorus content, and polyferric sulfate can combine with phosphate ion (PO ₄ ³⁻) in wastewater to form insoluble iron phosphate precipitation, so as to effectively remove phosphorus.
Strong adaptability: PFS can maintain good coagulation effect in a wide pH range, and is suitable for the variable water quality conditions of printing and dyeing wastewater.
Economic and environmental protection: the dosage of polyferric sulfate is small, the cost is low, and the treatment cost can be saved by 20%~50%. At the same time, it does not contain harmful substances such as aluminum, chlorine and heavy metal ions. It is non-toxic, harmless, safe and reliable. It is less corrosive to the treatment equipment, which is conducive to environmental protection and sustainable development.
In conclusion, polyferric sulfate is an effective agent for the treatment of printing and dyeing wastewater, which can remove pollutants such as pigment, phosphorus and organic matter, and has significant environmental and economic benefits.6628b57d9cfb764461