Printing and dyeing is a very large-scale engineering project, involving various process steps such as raw materials, semi-finished product processing, textile, printing and dyeing factories, and sorting. Dyes will be applied throughout the entire printing and dyeing process, resulting in wastewater. Due to the complexity of the water body in printing and dyeing wastewater, pollutants can be divided into two categories based on their origin: one comes from the introduction of chemical fiber raw materials themselves; Another type is the slurry, degreaser, dye, chemical additive, etc. used in the production process. Textile printing and dyeing wastewater has the characteristics of high water consumption, high proportion of organic chemical pollutants, high alkalinity, and large water transformation, and is one of the difficult industrial production wastewater to solve. The wastewater contains dyes, slurries, modifiers, degreasers, strong acids and bases, chemical fiber residues, sand compounds, carbonates, etc. The specific methods used to solve printing and dyeing wastewater include organic chemistry, biochemistry, chemical methods, and a combination of several processing processes. The pre-treatment in wastewater treatment is mainly aimed at improving the wastewater body, removing floating debris and residues that can immediately settle the foundation, adjusting the wastewater body and water flow rate, reducing the environmental temperature of the wastewater, and improving the overall practical effect of wastewater treatment, ensuring the reliability of all disposal operating systems. Therefore, preparatory treatment has a very important influence in the solution of printing and dyeing wastewater.

The treatment of printing and dyeing wastewater is the first to remove and alleviate pollutants from the production process. If using dry clothing printing processing technology, remove printing and dyeing wastewater. According to the characteristics of printing and dyeing wastewater, they should be recycled and reused separately, with multiple uses for one water; Using sedimentation and filtration methods to recover and utilize soil dyes and magnetized dyes, and using ultrafiltration methods to recover and utilize reducing dyes, dispersed dyes, etc.

Secondly, carry out harmless treatment of wastewater. For alkaline wastewater, a sewage tank is generally set up to ensure the necessary homogenization time; Regarding saturation, according to the regulations for wastewater discharge and utilization, chemical or physical methods such as coagulation, adsorption, air oxidation, and electrolysis of salt water can be used to solve the problem. It is also possible to shape unique bacteria and carry out fading under anaerobic standards.

Frequently asked questions:

(1) The coagulation method has a very good removal effect on the saturation of immediate dyes, reducing dyes, magnetized dyes, and dispersed dyes, but it has a poor actual effect on acid and alkaline dyes, reactive dyes, and fading.

(2) Activated carbon has selective adsorption properties for dyes, and has excellent adhesion properties for water-soluble dyes such as cationic dyes, immediate dyes, acid-base dyes, and reactive dyes. However, it has poor adsorption properties for insoluble dyes such as vulcanized rubber dyes, vat dyes, and building coatings.

(3) Common reactive oxygen oxides have a very good fading effect on absorbent dyes such as immediate dyes, acid-base dyes, alkaline cations, and reactive dyes, but their actual fading effect on hydrophobic dyes such as vat dyes, vulcanized rubber dyes, and dispersed dyes is poor.

There are many organic compounds in wastewater, and biological methods are usually used to achieve reliable practical results; For organic chemical slurries such as PVA, biodegradation or recycling methods can be used. In biological dissolution, high MLSS first and second stage hydrolysis acidification tanks and anaerobic fermentation aerobic acid treatment processes can be used separately; In recycling, various methods can be used, including gel precipitation (adding boron sand and sodium nitrate), coagulant method (such as using mirabilite and boron sand as coagulants), and ultrafiltration.

The selection of the solution process for printing and dyeing wastewater should be based on the raw materials, product varieties, production processing methods used in the production process, the drugs added throughout the processing process, the characteristics of dyes and modifiers, and their water output regulations. Each should adopt a primary organic chemistry and physicochemical solution or a secondary biological method as the main solution or a tertiary deep solution.

Membrane separation equipment is a new type of high-efficiency and environmentally friendly stripping technology. With the rapid development of membrane separation equipment in China, contemporary new technology membrane separation equipment (key technologies include ultrafiltration membrane, nanofiltration membrane, and membrane separation technology) has been widely and successfully applied in industrial production of printing and dyeing plants, and has formed good social and economic benefits, generating new trends for technological innovation in the field of textile printing and dyeing.

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