The invention provides a method for preparing high-purity
manganese sulfate through extracting low-grade
pyrolusite by using
rice straw. The method comprises the steps of adding a
sulfuric acid solution and dry
rice straw into
pyrolusite, reacting at the temperature of 70-950 DEG C for 8-15h while continuously stirring, and filtering to obtain
pyrolusite leachate; respectively removing heavy
metal ions such as iron ions, Ni<2+> and Co<2+> as well as
calcium and
magnesium ions by using an
ammonia solution,
barium sulfide and
ammonium fluoride to obtain an initial solution of
manganese sulfate; adding
ammonium carbonate to form a white
sediment, filtering, mixing the obtained
solid and 500-DEG C water, stirring for 10 minutes, filtering, mixing the obtained
solid and 500-DEG C water, stirring for 10 minutes, and then, filtering to obtain
solid manganese carbonate; and adding the
sulfuric acid solution to completely dissolve the solid manganese
carbonate, continuing to stir for 30 minutes, heating to concentrate the solution, crystallizing, centrifugally dehydrating, and
drying in hot air to obtain high-purity solid manganese
sulfate. By using the method, the process flow is simplified, the operation condition is improved, the
energy consumption is greatly reduced, and the industrial application prospect is huge.