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Use of Chlorine Dioxide
Published in Willy J. Masschelein, Unit Processes in Drinking Water Treatment, 2020
Chlorine dioxide can theoretically be considered as a mixed anhydride of chlorous acid and chloric acid: 2ClO2+H2O=HClO2+HClO3 However, in a neutral solution, chlorine dioxide hydrolyzes only poorly, although KH=HClO2⋅HClO3ClO22=1.2×10−7at20∘C The entire reaction is complex and involves disproportionations important in the design of chlorine dioxide generation systems.
Bleaching of Cellulosic and Synthetic Fabrics
Published in Menachem Lewin, Stephen B. Sello, Handbook of Fiber Science and Technology: Volume I Chemical Processing of Fibers and Fabrics, 2018
The use of sodium chlorite as a bleaching agent began in 1939, and despite its higher cost compared to H2O2 and NaClO it attracted wide interest due to several established advantages [117, 148, 163–167, 170, 171] : Sodium chlorite is an effective bleaching agent. It produces high-whiteness fabrics and at the same time appears to attack only the impurities of the cotton without visibly degrading the cellulose when applied at the range of conditions used in bleaching processes.Traces of metal ions do not catalyze the decomposition of sodium chlorite or chlorous acid, and do not bring about a degradation of cellulose.Sodium chlorite can be used advantageously for the bleaching of other cellulosic and noncellulosic fibers and their blends. It is particularly useful for rayons and flax for which mild bleaching agents and longer bleaching times are needed.A precooking or scouring stage is not essential, and since the cellulose is not degraded, conditions can be adapted to permit an even bleaching of cottons heavily contaminated with seed husks.The weight loss is lower, and due to the incomplete removal of the waxes, the hand of the chlorite-bleached fabric is softer as compared to NaClO and H2O2 bleaches.Due to the acid conditions of the bleaching, only a slight swelling of the fabric is obtained.The bleached fabrics have low residual alkali, which facilitates removal of chemical residues. Relatively small amounts of water are needed for rinsing and removing the chlorite bleach liquor.
Preparation and characterization of lotus fibers from lotus stems
Published in The Journal of The Textile Institute, 2018
Cheng Cheng, Ronghui Guo, Jianwu Lan, Shouxiang Jiang, Zoufei Du, Ludan Zhao, Linghui Peng
Sodium chlorite not only dissolves extra epidermis but also removes abundant lignin and hemicellulose in S1 during purification treatment. Equation (5) shows the ionization balance between chlorite () and chlorous acid (HClO2) in acid solution. The disproportionation reaction of HClO2 can form hypochlorous acid (HClO) as shown in Equation (6). The Chemical HClO2 is consumed by HClO and intermediate product Cl2O2 is produced (Equation (7)). This intermediate product further forms ClO2 (Equation (8)) in subsequent reactions (Lehtimaa, Kuitunen, Tarvo, & Vuorinen, 2010). The chemical ClO2 is the dominate specie during the purification of S1 with sodium chlorite. The bonds between lignin and cellulose are broken and the chemical structure of lignin is damaged due to the oxidation of ClO2 (Liu, Li, Zhang, Zhang, & Xu, 2016). Therefore, the impurities that have not been completely removed including lignin, hemicellulose, pectin, and other non-cellulose substances can be dissolved into acid sodium chlorite solution. The content of cellulose of sample is enhanced.