| 摘要 |
<p>Prodn. of (NH4)6Mo7O24.4H2O (I) comprises first leaching a MoO3 concentrate in H2O at 70-95 degrees C (solids content 5-50%) for a time sufficient to extract at least part of the contaminating metal ions into the aq. phase. The leached concentrate is then sepd. from the aq. extract, and soluble molybdates are recovered from the latter. The leached concentrate is then leached with NH4OH soln. to extract NH4 molybdates, and the extract is sepd. from the insoluble residue and concd. in an evaporator to form a satd. soln. of NH4 molybdates. The satd. soln. is (partly) withdrawn and adjusted to a NH3:MoO3 molar ratio of 0.86-1.25:1, and is then cooled to ppte. crystals of (I). These are sepd. from the mother liquor, which is recycled for mixing with a fresh batch of ammoniacal extract entering the evaporator. (I) is used as an analytical reagent, for the prodn. of pigments and catalysts (e.g. for petroleum refining and coal treatment) and for the prodn. of metallic Mo. The process does not require a purified MoO3 starting material, air-roasted molybdenite concentrates are suitable.</p> |
