Biocides, oxidizing sodium hypochlorite

Uncooked starch suspensions can easily spoil. If suspensions are to be held for more than a few hours, a preservative (biocide) needs to be added. Some commonly used reagents, such as chlorine or sodium hypochlorite, will attack (oxidize) starch. This reaction has to be considered when choosing a preservative. 

Biocides are used widely in industry. There are at least three main classes of industrial chemical biocides. The first class includes the oxidizing and bleaching agents, such as chlorine dioxide, hydrogen peroxide, and sodium hypochlorite. The oxidizing action may directly kill bacteria or fungi or weaken the cell walls so that they are more susceptible to other classes of biocides (see below). Sodium... 

Typical biocides include hypochlorous acid, chlorine dioxide, hypobromus acid, hydrogen peroxide, ozone, ultraviolet-light treatment, phenolics, aldehydes, and quaternary ammonium compounds (Ref 73, 80). A brief description of each follows (Ref 73, 80). Hypochlorous acid is probably the most commonly used biocide and also one of the most powerful oxidizing agents. The sources of hypochlorous acid are chlorine gas and sodium hypochlorite. In aque-... 

Chlorine gas and sodium hypochlorite are used in fresh water and process water (white water) applications. Some mills are also using hypochlorite for thickstock applications. Because bleach is a relatively cheap commodity chemical, many mills are increasing application of this oxidant to reduce biocide costs. However, bleach can be very aggressive towards papermaking equipment and chemicals. 

---