Reduction of sulfates by hydrogen

Abstract

The initial stage of reduction of anhydrous sulfates by H 2 may lead to the formation of any of the following: (1) sulfates at lower valency, e.g., reduction of CuSO 4 , HgSO 4 , Fe 2 (SO 4 ) 3 ; (2) metals, e.g., Cu 2 SO 4 , Ag 2 SO 4 ; (3) sulfides, e.g., NiSO 4 , CoSO 4 , CdSO 4 , CaSO 4 , SrSO 4 , BaSO 4 , and alkaline metal sulfates; (4) oxides, e.g., Al 2 (SO 4 ) 3 , MgSO 4 , BeSO 4 ; (5) a mixture of oxide and sulfide, e.g., FeSO 4 , MnSO 4 , ZnSO 4 , PbSO 4 . While CuSO 4 , Ag 2 SO 4 , and PbSO 4 are the only sulfates that yield metals on reduction, CuSO 4 is the most interesting because it yields the metal at 350 °C. PbSO 4 is reduced to metal at about 800 °C, and Ag 2 SO 4 already yields the metal by thermal decomposition above 800 °C.