"Asbestos Use in Chlorine Manufacturing
Manufacturing chlorine has been in practice for well over a century, though many plants still use more toxic and unsafe methods to produce it. In general, the industry relies on three basic manufacturing processes:
The mercury cell process
The diaphragm cell process
The membrane cell process
All of these processes rely on the same basic chemistry. Chlorine and its co-products are created by electrolysing a salt solution with a direct electric current that ultimately converts chloride ions into chlorine. While the mercury cell process is decreasing globally and much of Europe has adopted the safer option of the membrane cell process, several plants in America still use diaphragms made from asbestos.
The diaphragm cell process works with a combination of water and sodium chloride to create a brine solution, which is processed and filtered to remove impurities. Heat is applied to the solution and more salt is added until the purified brine solution is prepared for the electric current, which is where the asbestos materials come into play.
An asbestos diaphragm is usually used to separate the cathode and anode, which will create the current. Though the United States Geological Survey noted in a recent asbestos study that more plants are looking for alternatives for the asbestos diaphragms, at least 15 plants in the United States still use these products today. According to the EPA, a typical plant will use anywhere from 5 – 25 tons of asbestos each year in production of these diaphragms.
The industry relied on making asbestos diaphragms because of the mineral's durability and chemical resistance. These properties help the diaphragm prevent the caustic soda also being produced in the process from reacting with the chlorine."
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