ABSTRACT
Extensive industrial use of mercury has led to significant pollution of the environment. Mercury introduced to the natural environment, regardless of the form can be relatively easily converted into highly toxic volatile and water soluble forms, i.e. methyl-or ethyl-mercury chloride, far more bioavailable and much more toxic than other forms of mercury. Furthermore, mercury is highly retained in living organisms, and therefore becomes biomagnified. Hence, mercury is a very dangerous, global pollutant because of its extreme toxicity, global atmospheric transport and accumulation in the food chain. (Boening 2000)
Today, the major anthropogenic sources of mercury emissions to the environment include the burning of coal to produce electricity, the incineration of waste and the chlor-alkali technology.The chlor-alkali industry produces chlorine and alkali, sodium hydroxide or potassium hydroxide, by electrolysis of brine. The main technologies applied for chlorine and alkali production are mercury-, diaphragm-and membranecell electrolysis. The mercury-cell (amalgam) process has been in use, mainly in Europe, since 1892 and now still accounts for ca. 50% of total production of chlorine in Europe. In the EU and EFTA countries there are presently about 50 operating mercury-cell chlor-alkali installations, with a chlorine production capacity of over 5.8 million tons per year. In line with the commitment of Euro-Chlor members, these plants will be decommissioned and/or converted to an alternative mercury-free process by 2020, as will a
number of mercury-cell chlor-alkali plants in the US and other countries. Considering only the European mercury-cell plants, this decommissioning activity will release ca. 12 000 tons of process mercury, and even if mercury-cell processes are phased out in the European Community they will be still operating in Eastern Europe and developing countries worldwide. (Eurochlor 2006)
Due to the amalgam chlor-alkali technology characteristics, mercury can be emitted to the environment through air, water, solid wastes and in the products. Total mercury emission from chlor-alkali plants in Europe was about 40 tons in 2006, ranging from 0.15 to 3.0 g Hg per t of chlorine produced at the individual plants. As it was mentioned mercury is a dangerous global pollutant and therefore removal of mercury from industrial emissions in all possible places is mandatory and should take into account the latest achievements in science and technology.
