Bleaching Paper

These rosin-based sizes, whether paste, Hquid, or emulsions, can be used to size all grades of paper that are produced at acid pH. The latter include bleached or unbleached kraft Hnerboard and bag paper, bleached printing and writing grades, and cylinder board. In addition, polyaluminum compounds have been used in place of alum, most notably, polyaluminum chloride (48), which can reduce barium deposits where these have been a problem. The barium chloride by-product is more water-soluble than barium sulfate. Other polyaluminum compounds such as polyhydroxylated forms of alum and polyaluminum siHcosulfate have been evaluated as alum replacements. 

Sodium sulfite [7757-83-7] which is used in pulp and paper bleaching, is usually produced by the reaction of sulfur dioxide with either caustic soda or soda ash. 

Uses Metallurgy (e.g., making steel), metal fabrication, chemical manufacture, medical and life-support applications, sewage treatment, rocket propellant, paper bleaching. 

Uses Chlorine is used for water purification and in decreasing amounts for pulp and paper bleaching. Some is used for metallurgical purposes such as metal extraction. Its largest use is for the production of organic compounds used in plastics, pesticides, herbicides, refrigeration fluids, solvents, and others. 

The bleaching process, in contrast, poses major difficulties. Traditional paper bleaching uses chlorine gas, which is reduced to chloride anions, cr, as it oxidizes the colored pigments in wood pulp. The chloride anion is not a pollutant, as it is a major species in the oceans. Unfortunately, chlorine processing also generates small quantities of chlorine-containing dioxins such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin, whose stmcture (below) appears less formidable than its name ... 

IR spectrophotometry, 661, 662 TEARS assay, 667 hydroperoxide oxidation, 692 Upid hydroperoxides, 977-8 decomposition, 669 DNA adducts, 978-84 protein adducts, 984-5 ozone adducts, 734 ozonide reduction, 726 ozonization characterization, 737, 739 peroxydisulfate reactions, 1013, 1018 Alkali metal ozonides, 735-7 Alkaline peroxide process, pulp and paper bleaching, 623... 

Packing class, commercial codes, 621 Packing effect, dialkyl peroxides, 121 Palm olein, oxidative deterioration, 662 Pamctinal laser photocoagulation, 640 Paper, bleaching agents, 623 Parasites... 

Minute amounts of dioxin are created in certain combustion processes and by a few chemical manufacturing processes, including the use of chlorine in paper bleaching. 

Ryan et al. (1992) analyzed the concentrations of CDDs/CDFs in Canadian bleached-paper milk containers from 1988 to 1989 and examined the resulting concentrations transferred to the milk. Milk-carton paper manufactured prior to 1989 tested positive for 2,3,7,8-TCDF and 2,3,7,8-TCDD, with levels on a TEQ basis varying between 1.4 and 55 ng/kg of paper. Bleached milk-carton paper produced after mid-1989 tested negative for these compounds at a limit of detection of 1 ng/kg paper. Storage of 3 types of milk in the pre-1989 low- and high-level cartons resulted in the transfer of the TCDD/TCDF into the milk, most of which occurred within the first 7 days. The TCDD/TCDF transfer varied between 3 and 25%, with whole and 2% fat milk accumulating about twice the concentrations of skim milk. On the basis of these results, milk stored for up to 14 days at 5 °C in currently produced bleached-paper containers with less than 1 ng TEQ/kg of paper would not contain any detectable CDDs/CDFs (<0.005 ng TEQ/kg milk). 

In other oxygen applications, metal fabrication involves cutting and welding with an oxygen-acetylene torch. Chemical manufacture use includes the formation of ethylene oxide, acrylic acid, propylene oxide, and vinyl acetate. Miscellaneous uses include sewage treatment, aeration, pulp and paper bleaching, and missile fuel. 

Dioxin is formed as a by-product of many industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing, and pulp and paper bleaching. Dioxin was the primary toxic component in Agent... 

Hydrogen peroxide is a green chemical that only leaves water or 02 as byproducts. Thus, it is increasingly used to bleach pulp and paper, bleach... 

Acetate Tow A yellowish powder that is a byproduct of paper bleaching, used for cigarette filters and medical gauze. 

This chapter will focus on three important industries where peroxygens have had a significant impact, particularly with respect to environmental issues chemical purification, pulp and paper bleaching and hydrometallurgy and metal finishing. 

Oxidation-reduction reactions, also known as redox reactions, are chemical processes in which electrons are transferred from one atom, ion, or molecule to another. Explosions, fires, batteries, and even our own bodies are powered by oxidation-reduction reactions. When iron rusts or colored paper bleaches in the sun, oxidation-reduction has taken place. 

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