27 октября, 2015 
Pokraskin Since alkali dichromates or chromic acid anhydride are used as starting materials for the production of chromium(III) oxides, occupational health requirements for the handling of hexavalent chromium compounds must be observed [3.69]. The sulfur dioxide formed on reduction with excess sulfur must be removed from the flue gases according to national regulations, e. g., by oxidation and absorption to H2SO4.
Process wastewater may contain small amounts of unreacted chromates; recovery is uneconomical. Prior to release into drainage systems, the chromates in these wastewater streams must be reduced (e. g., with SO2 or NaHSO3) and precipitated as chromium hydroxide [3.70]. In Germany, for example, the minimum requirements for wastewater in the production of chromium oxide pigments are specified in Ref. [3.71].
3.1.2.3
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