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Elemental chlorine free (ECF) is a technique that uses chlorine dioxide for the bleaching of wood pulp. It does not use elemental chlorine gas during the bleaching process and prevents the formation of dioxins and dioxin-like compounds , carcinogens .
Chlorine dioxide is sometimes used in combination with chlorine, but it is used alone in ECF (elemental-chlorine-free) bleaching sequences. It is used at moderately acidic pH (3.5 to 6). The use of chlorine dioxide minimizes the amount of organochlorine compounds produced. [8]
Elemental chlorine bleaching uses chlorine and hypochlorite. Elemental chlorine-free bleaching is more environmentally friendly since it eliminates the use of hypochlorite and replaces chlorine with chlorine dioxide or sodium chlorate. [3] Totally chlorine-free bleaching utilizes oxygen and hydrogen peroxide. This is the most environmentally ...
The worst, elemental chlorine, releases highly toxic dioxin into wastewater, but its use has mostly been eliminated. The most popular method now is elemental chlorine free (ECF) bleach — which ...
In the past, plants using elemental chlorine produced significant quantities of dioxins, [35] persistent and very toxic organic pollutants. From the 1990s onward, the use of elemental chlorine in the delignification process was substantially reduced and replaced with ECF (Elemental Chlorine Free) and TCF (Totally Chlorine Free) bleaching processes.
Chlorine is too reactive to occur as the free element in nature but is very abundant in the form of its chloride salts. It is the 20th most abundant element [71] in Earth's crust and makes up 126 parts per million of it, through the large deposits of chloride minerals, especially sodium chloride, that have been evaporated from water bodies.
The Kappa number estimates the amount of chemicals required during bleaching of wood pulp to obtain a pulp with a given degree of whiteness. Since the amount of bleach needed is related to the lignin content of the pulp, the Kappa number can be used to monitor the effectiveness of the lignin-extraction phase of the pulping process.
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