Recycled paper bleaching

Paper,recycled -H202 bleaching of [HYDROGEN PEROXIDE] (Vol 13)... 

Reductive bleaching -m paper recycling [RECYCLING - PAPER] (Vol 21)... 

Both for the environment and for yourself, it s best to use recycled paper as much as possible. Toilet paper from the natural products store is an acceptable substitute for the more luxurious non-recycled toilet paper which is chemically bleached and often colored and perfumed. 

Hypochlorites (OCI ). Hypochlorite bleach solutions are made from NaOCl and, to a lesser extent, Ca(OCl)2. Hypochlorites are used in laundering, as disinfectants, in the bleaching of pulp and textiles, and in the removal of ink from recycled paper. Commercial bleaching solutions are obtained by passing chlorine gas through cold, dilute, aqueous sodium hydroxide, as shown in equation 7. 

Closed-Mill Concept. The closed-mill concept, or water circuit closure, has been studied by the pulp and paper industry for many years. In some parts of the paper manufacturing process, up to 98% of the water is recycled within the process, eg, the wet end of the paper machine. However, in the pulp mill, especiaUy kraft mills, effluents are produced owing to the need to purge from the system various metals that come in with the wood, as weU as organic by-products from the pulping process, additives, and especially chloride ions that originate in the bleach plant. 

This growth will substantially increase demand for surfactants, bleaching agents, complexing agents, and other chemicals used in paper recycling... 

Bleaching is defined as any process that chemically alters pulp to increase its brightness. Bleached pulps create papers that are whiter, brighter, softer, and more absorbent than unbleached pulps. Bleached pulps are used for white or light colored paper. Unbleached pulp is typically used to produce boxboard, linerboard, and grocery bags. Of the approximately 65.5 million T (72 million tons) of pulp (including recycled pulp) used in paper production in the U.S. in 2000, about 50% is for bleached pulp.1... 

Hydrosilation inhibitors, in paper release coating fabrication, 22 591-592 Hydrosilation silicone, heat-curable, 10 5 Hydrosilylation. See also Silylation monoallyl derivatives, 2 242 products of, 22 552-554 Hydrosorbic acid, physical properties, 5 31t Hydrostatic cooker, 12 81 Hydrostatic lubrication, 15 212 Hydrosulfide salts, oxidation of, 23 633 Hydrosulfite bleaching, 21 50, 52 of recycled pulps, 21 52 Hydrosulfite-induced reductive-cleavage, 9 439-140... 

When bleaching wood pulp in a paper mill, the amount of leftover or residual hydrogen peroxide present in the spent bleach liquor can be important. Sometimes the bleach liquor is used in a second bleach or recycled back to the first bleach. Also, the residual peroxide level can indicate whether the bleach liquor makeup needs adjusting. Laboratory scale bleach tests are performed on the wood pulp, and the residual peroxide levels are checked by titration of the spent bleach liquors using potassium iodide and sodium thiosulfate. By monitoring the residual peroxide levels of these bleaches, the bleach liquor makeup can be adjusted, giving the best level, as needed by each paper mill. 

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