Bleaching, with chlorine

Pulp bleaching with chlorine dioxide is most often performed at an acidic pH, so that the final pH of the bleach Hquor is in the range of 2—5. Under these conditions, the residual concentration of chlorite and chlorate ions in the bleach Hquor are minimized and chloride ion is the predominant chlorine species in the spent bleach (77). In addition to direct addition to pulp in bleaching, chlorine dioxide also finds use in wastewater treatment from pulp mill operations as a means to remove effluent color (85). 

Dioxin and furan. During the late 1980s, bleaching with chlorine and hypochlorite were discovered to be a source of dioxin and furan. Although the use of chlorine dioxide (ClOj) bleaching minimizes the formation of chlorinated pollutants, measurable quantities of... 

Celdecor A process for making paper from straw or bagasse. The fiber is digested in aqueous sodium hydroxide and bleached with chlorine. The essential feature is that the alkali and chlorine are used in the proportions in which they are made by the Chlor-Alkali process. 

Elementary chlorine-free (ECF) process. Using modifications to the standard process, such as alternatives to free chlorine in the form of chlorine dioxide (delivered by sodium chlorate), prolonged cooking times, and prebleaching with oxygen before the main bleaching with chlorine dioxide, about the same quality of paper was reached without the drawbacks of elementary chlorine (see Table 6.4). 

The removal of excess chlorine or hypochlorous acid from fabrics which have been bleached with chlorine ... 

During 1988, the EPA and the U.S. pulp and paper industry jointly conducted a survey of 104 pulp and paper mills in the United States to measure concentrations of CDDs in effluent, sludge, and paper (EPA 1990d). This study is commonly called the 104-Mill Study and includes all U.S. mills where wood pulps are bleached with chlorine or chlorine derivatives. Higher chlorinated CDDs/CDFs are typically found in effluent when chlorine dioxide is used, but not when elemental chlorine is used. In 1992, the pulp and paper industry conducted its own survey (NCASI 1993). As part of an effort to develop revised effluent guidelines and standards for the pulp and paper industry, the EPA recently published the development... 

Before the pulp can be made into paper, it is necessary to mechanically beat or refine it. It is also usually bleached with chlorine and calcium hypochlorite. Unbleached kraft pulp is used for grocery bags and heavy wrapping paper. Other materials may also be added to the pulp depending on the type of paper to be made. For book paper, fillers such as white clay and titanium oxide may be added to provide opaqueness and extra whiteness. Size may be added for stiffness and smoothness. Dyes are added for tinted papers. The specific combination of pulp and additives used to produce a particular type of paper is called the furnish for that paper. With better grades of paper, care is taken to produce a furnish that is chemically neutral (pH 7 on the acid-base scale). For a paper to have long life, it must be acid-free. 

While the results of the Wohler-Liebig paper could easily be fitted into Berzelius scheme, a parallel development could not. Some candles bleached with chlorine had given off highly irritating vapors at a gathering at the Tuileries. Dumas was asked to investigate the problem. Chlorine, it turned out, had replaced hydrogen in the wax, volume for volume, or equivalent for equivalent as... 

A measure of the amount of chlorine that is chemically bound to the soluble organic pollutants in the effluent. Collective term for the several hundred chlorinated compounds formed during bleaching with chlorinated chemicals. It is also formed naturally. Some of these substances accumulate in fish and fish-eating birds. 

One plant in Sweden produces 315,000 ton/yr of pulp that is bleached with ozone. The pulp is just as strong as the standard pulp bleached with chlorine. Almost all (95%) of the effluent waste is recycled.98 Ozone is also being used to bleach Eucalyptus in Brazil.99 Dioxiranes work well in bleaching pulp. They can be generated in situ from a ketone and peroxymonosulfate ion (3.11).100... 

Nemetz, Thomas M., and Ball, David W. (1993). Bleaching with Chlorine Another Tomato Juice Demonstration. yo rw / of Chemical Education 70(2) 154-155. 

Thus, flour bleached with chlorine dioxide contains little or no tocopherol. On the other hand, no measurable loss occurs when similar white flour is bleached using ascorbic acid or potassium bromate (Moore et al., 1957). 

Ivaska A, Forsberg P, and Heikka R (1990) Application of an amperometric sensor to in-line monitoring of pulp bleaching with chlorine dioxide. Analytica Chimica Acta 238 223-229. 

Berthollet, Claude-Louls (1748-1822) French physician and inorganic chemist whose ideas on the formation of chemical compounds, although mistaken, led other workers to come nearer to the truth. He made important advances in dye-making, bleaching with chlorine, and steel making. His two major published works were Researches into the Laws of Chemical Affinity (1801) and Essay on Chemical Statics (1803). 

The careful removal of lignin by bleaching does not always remove the extractives, however. For example, chlorination of unsaturated fatty acids increases the difficulty of saponification on subsequent treatments. In addition the resin becomes more hydrophobic. If the resin acids are chlorinated, their solubility is decreased and their ability to solubilize neutral resin substances such as sterols is reduced. On the other hand, bleaching with chlorine dioxide produces components that are easily saponified with alkali, and the free acids can solubilize some of the other components (13). 

Table 11.14 Chlorinated fatty acids in flour bleached with chlorine.

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