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Minamata Convention - Primary Zinc metallurgical industries worldwide

About 90% of world’s total zinc output is produced from zinc sulphide concentrates through conventional hydro-metallurgical route i.e. Roast – Leach – Electro-win (RLE) process.

These zinc sulphide concentrates invariably contain varying amounts of mercury. [Pls. refer click: http://www.slideshare.net/prchandna/zinc-smelter-concept-note page 19]

The pre-requisite condition of zinc metal extraction from sulphide concentrate through a hydro-metallurgical process route is the elimination of its sulphur content in order to make it amenable to further treatment by leaching and then electro-winning processes.

This is predominately accomplished by roasting of zinc sulphide concentrates in fluid bed roasters and the fixation of SO₂ bearing off – gases thus generated as sulphuric acid by double contact process.

1 (One) tonne of Zinc metal co-produces approximately 1.8 (One point eight) tonnes of Sulphuric acid. [Please refer click:  http://www.slideshare.net/prchandna/zinc-smelter-concept-note page 18].

The present zinc production capacities in India have grown in geometric proportion to One million tonnes per annum in the past one decade.

The bye-product Sulphuric Acid thus produced at zinc smelters are utilized to produce phosphoric acids, which is further used for production of various types of fertilizers.

During roasting operations at 1000-1100 °C, almost all the mercury contents of the zinc sulphide concentrate fed to roasters gets volatilized and carried along with the SO₂ bearing off-gases, which is further converted to Sulphuric Acid manufacture.

Unless, the well proven technologies, which are already available worldwide, are installed and operated religiously by the Zinc metallurgical industries in the country, to remove and recover the mercury contained in the zinc sulphide concentrate fed into these smelters, all the mercury metal is compulsorily entering into fertilizers [entering the food chain] and are being served to us on our plates starting every day morning at breakfast till at dinner, subjecting all of us to mercury poisoning – a well-known disease ‘MINAMATA’.

View these Videos:  
Mercury Poisoning- The Minamata Story http://www.youtube.com/watch?v=ihFkyPv1jtUThe Minamata Disease Truth http://www.youtube.com/watch?v=LdKG1Y2XFN0