What are the applications of Thiourea dioxide in paper making industry

Thiourea dioxide also call FAS in paper making. FAS can bleach because Sulfoxylic acid and dilute sodium sulfate decomposed in alkaline solution have reducibility. When bleaching, it can change the structure of the chromophore group in the pulp, reduce the absorption of light, and improve the brightness of the pulp. FAS bleaching is easy to operate, with good bleaching effect and pollution-free wastewater, which can be directly discharged into farmland.
1. NaOH to FAS dosage ratio. Considering the chemical cost and bleaching effect, a ratio of 2 NaOH to FAS is more suitable.
2.Bleached pulp concentration. Generally speaking, an increase in the concentration of bleached pulp results in a corresponding increase in the effective concentration of chemicals during bleaching, which is beneficial for improving bleaching efficiency. However, as long as the mixture is uniform, FAS bleaching is feasible at medium or high concentrations.
3.FAS dosage. The whiteness of waste paper deinked pulp increases with the increase of FAS dosage at different bleaching temperatures. When the FAS dosage is less than 0.3%, the whiteness increases significantly; When it exceeds 0.6%, the whiteness increases slowly.