The environmental measures for bleaching fabrics mainly include using environmentally friendly bleaching agents, optimizing bleaching processes, treating bleaching wastewater, and recycling bleaching by-products.
Use environmentally friendly bleach
Sodium hypochlorite: Sodium hypochlorite is a common environmentally friendly bleaching agent, and its effective chlorine content is usually controlled within the range of 3-5 g/l. The ph value is adjusted to about 10 with caustic soda. The bleaching process of sodium hypochlorite is relatively simple and suitable for bleaching cotton fabrics and blended fabrics, but not for protein fibers such as silk and wool.
Hydrogen peroxide: Hydrogen peroxide is widely used due to its excellent bleaching effect and pure color light. Compared to sodium hypochlorite, hydrogen peroxide does not cause accidental chemical damage and is particularly suitable for treating plant stains such as tea, coffee, and red wine.
Optimize bleaching process
Control ph value: The optimal ph values for sodium hypochlorite bleaching are 2-4 and 9-11 to reduce fiber damage. The ph value of hydrogen peroxide bleaching should be adjusted to 10-11 to optimize the bleaching effect.
Control temperature and time: The temperature for sodium hypochlorite bleaching should be controlled between 20-35 ℃, and the time should be set between 30-60 minutes. The high-temperature steaming time for hydrogen peroxide bleaching is 45-60 minutes.
Concentration control: The effective chlorine content of sodium hypochlorite should be controlled at 1-5g/l, and the effective component of hydrogen peroxide should be controlled at 2-6g/l.
Treating bleaching wastewater
Dechlorination treatment: After bleaching with sodium hypochlorite, dechlorination treatment is required to remove residual chlorine gas and prevent fabric yellowing and strength loss during storage. Common dechlorination agents include hydrogen peroxide, sodium bisulfite, etc.
Wastewater treatment: Bleach wastewater needs to undergo steps such as washing, dechlorination, and re washing to ensure effective treatment of harmful substances in the wastewater and avoid environmental pollution.
Recycling and reusing bleaching by-products
Recycling hydrogen peroxide: During the bleaching process, hydrogen peroxide can be recycled and reused, reducing resource waste and costs.
Processing by-products: Sodium chloride produced by sodium hypochlorite bleaching can be recycled and reused to reduce waste emissions.
