Method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide

Abstract

Provided is a method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, which sequentially comprises: (1) mixing manganese oxide ore and pyrite, continuously feeding the mixture and sulfuric acid into a continuous leaching tank to form a one-stage or multi-stage continuous leaching, removing potassium ions first after leaching, and then removing iron by means of a neutral iron removal method, and adding lime powder at the late stage of iron removal to adjust the pH value of the solution to 6-6.5, so as to obtain a manganese sulfate solution after reaction at 90-95° C. for 3-4 hours; (2) performing purification and impurities removal on the manganese sulfate solution by a two-stage continuous purification process, wherein, during the first stage of the continuous purification on the manganese sulfate solution, calcium polysulfide is added, and during the second stage of the purification, the solution passes through a sluice and calcium and magnesium are dynamically removed, and then the solution is sent to a still tank to stand to deposit and remove impurities such as calcium and magnesium; and (3) subjecting the purified manganese sulfate solution to ultra-fine filtering, heating to 90-100° C. by a plate heat exchanger, and then entering an elevated tank, and at the same time, adding a prepared suspending agent and a prepared foaming agent, and supplying the resulting product to electrolysis baths through pipelines for electrolysis, so as to obtain mercury-free alkaline-manganese type electrolyzed manganese dioxide. The method has the advantages of wide adaptability to manganese oxide ores, short process flow, and low production cost.

1 . A method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide, comprising the following sequential steps:
 (1) mixing manganese oxide ore and pyrite, continuously feeding the mixture and sulfuric acid into a continuous leaching tank composed of 1-7 stirring leaching tanks to form a one-stage or multi-stage continuous leaching, controlling the reaction temperature at 90-95° C. for about 3 to 4 hours during the process, removing potassium ions first after leaching, and then removing iron by means of a iron removal-method by neutralization, and adding lime powder at the late stage of iron removal to adjust the value of the solution to 6-6.5 at 90-95° C. for 3-4 hours, so as to obtain a manganese sulfate solution;   (2) performing purification and impurities removal from the manganese sulfate solution by a twice-stage continuous purification process, wherein, during the first stage of the continuous purification of the manganese sulfate solution, calcium polysulfide is added, at the controlled temperature of 60° C., and then performing the second stage of the purification, during which the solution passes through a sluice and the calcium and magnesium are dynamically removed, and then the solution is sent to a stand tank to left for 32 hours to ageing and remove impurities such as calcium and magnesium as precipitate;   (3) subjecting the purified manganese sulfate solution to ultrafiltration, heating the solution to 90-100° C. by a plate heat exchanger, and then entering it into an elevated tank, and adding the prepared suspending agent and foaming agent at the same time, and supplying the resulting product to electrolysis baths through pipelines, electrolysis conditions: electrolyte temperature is 100-103° C., the anodic current density is 80-85 A/m 2 , the cell voltage is 2.2-3.5V, electrolytic period is 12-20 days, after electrolysis the mercury-free alkaline-manganese type electrolyzed manganese dioxide is obtained.   
     
     
         2 . The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to  claim 1 , wherein the step 1 further comprises; directly feeding the manganese oxide ore and pyrite into the continuous leaching tank by the ratio of 1:0.24, at the same time blending sulfuric acid and waste electrolyte the ratio of 1:0.47. 
     
     
         3 . The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to  claim 2 , wherein said waste electrolyte come from the raffinate liquid generated during the electrolysis in the step 3. 
     
     
         4 . The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to  claim 1 , wherein the step 3 further comprises broking the crude electrolyzed manganese dioxide products obtained during the electrolysis on the anode into particles of 6-8 mm, sending the particles into rinse ranks; using the three-stage rinsing process consisted of washing by water-caustic washing-washing by water, wherein, the temperature of the alkali liquor of the first and the second rinsing are both 60-70° C., the temperature of the water of the last washing is 80-90° C., the rinsing period is about 40 hours, and the rinsing liquids are directly heated by steam, and then obtaining the electrolyzed manganese dioxide with required particle size through milling. 
     
     
         5 . The method for producing mercury-free alkaline-manganese type electrolyzed manganese dioxide according to  claim 4 , further comprising sending the milled electrolyzed manganese dioxide into gravity mixing silos by the dense phase conveying mode to homogenization mixing, and the time of mixing is about 16 hours.