Group 6 metals, dithiocarbamate chromium

There are two treatability groups of dissolved metals for chemical precipitation, complexed and non-complexed metals. Non-complexed metals can be removed by a direct precipitation with such a chemical as lime (Ca(OH) ), caustic (NaOH), sodium sulfide (Na2S), ferrous sulfide (FeS), or sodium carbonate (NajCOj). Complexed metals require coprecipitation with ferrous sulfate (FeS04), ferrous chloride (FeClj), or sodium dimethyl dithiocarbamate (DTC) in addition to a regular precipitant such as caustic or lime. Electrochemically generated ferrous ion is also effective in removing a wide variety of heavy metals, including hexavalent chromium. 

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