1. Reduction dissolution of sulfur dyes
Mechanism of action: Sulfur dyes are insoluble in water and need to be reduced to soluble leuco forms under alkaline conditions before they can be adsorbed on fibers. Sodium hydrosulfide (NaHS), as a strong reducing agent, can replace traditional sodium sulfide (Na₂S) to reduce dyes to leuco forms in alkaline dye baths.
Advantages: Compared with sodium sulfide, NaHS requires less dosage, has milder reaction conditions, reduces the generation of by-product hydrogen sulfide (H₂S), and improves the production environment.
2. Dechlorination after dyeing
Application scenarios: Some dyeing processes (such as bleaching or oxidation dyeing) may leave residual chlorine (such as hypochlorite). Sodium hydrosulfide can neutralize the residual chlorine through reduction to avoid fiber damage or color distortion.
3. Post-dyeing cleaning and wastewater treatment
Removal of floating colors: Use sodium hydrosulphide 70% to clean the fabric after dyeing to restore the unfixed dye molecules, reduce floating colors, and improve color fastness.
Wastewater decolorization: In printing and dyeing wastewater, NaHS can reduce oxidative pollutants (such as azo dyes) and reduce the color and toxicity of the wastewater.
4. Other auxiliary purposes
pH adjustment: In alkaline dyeing systems, NaHS can help maintain the pH stability of the dye bath.
Fiber pretreatment: Some cellulose fibers (such as cotton) may be oxidized, and NaHS is used to reduce impurities on the fiber surface and enhance dyeing uniformity.
Post time: Apr-18-2025
