Research On The Technology Of Recovering Manganese Metal From Wastewater And Preparing High Purity Manganese

As an important strategic resource,electrolytic manganese is widely used in fields such as steel smelting,non-ferrous metallurgy and electronic industry due to its high purity and low impurities.However,due to the limitations of existing processes,the production process of electrolytic manganese will generate a large amount of manganese containing wastewater.At present,most enterprises use sedimentation method to treat manganese containing wastewater,and the manganese in the wastewater is removed in the form of manganese slag.This not only pollutes the environment,but also endangers human health,and also causes serious loss of manganese resources.Therefore,how to efficiently treat manganese containing wastewater to reduce environmental pollution and achieve manganese resource recycling has become an urgent problem to be solved in the electrolytic manganese production industry.A dedicated process is developed to study the water quality characteristics of smelting wastewater in the production process of electrolytic manganese.A process of enrichment concentration membrane electrolysis recovery secondary electrolysis purification is adopted to improve the purity of manganese and maximize the utilization of manganese resources on the basis of achieving manganese recovery in wastewater.The study first used ion exchange method to enrich metal Mn²⁺in wastewater,and selected Na type strong acidic cation exchange resin as the adsorbent.Through static and dynamic adsorption experiments,the effects of resin dosage,p H value,adsorption time,flow rate,and resin layer height on the adsorption efficiency of Mn²⁺were investigated.In the experimental study of controlling variables,the optimal parameters for static adsorption experiments were determined as follows:resin dosage of 0.3g,p H value of 6.0,adsorption time of 180 minutes.Under the optimal parameter conditions,the adsorption rate of Mn²⁺on the resin was 95.63%;The optimal parameters for dynamic adsorption are:flow rate of 8m/h,resin layer height of 90cm,exchange time of 3h,and the highest adsorption rate at 95.8%.Afterwards,a resin elution regeneration experiment was conducted,and the reverse countercurrent regeneration process was selected.The optimal regeneration parameters were determined as follows:a Na₂SO₄solution with a regeneration solution concentration of 8%,a regeneration solution flow rate of 2 m/h,a regeneration specific consumption of 1.6,and a enriched Mn²⁺concentration of 32.5 g/L,with an elution efficiency of over 99%.This achieved the enrichment and concentration of Mn²⁺.After the ion exchange process,the stepwise precipitation method is used to purify and remove impurities from other metal ions(Fe²⁺,Mg²⁺,Zn²⁺)in the enrichment solution,providing a relatively pure electrolyte for subsequent membrane electrolysis experiments.The membrane electrolysis method is used to treat enriched and concentrated manganese containing wastewater.The cathode solution is the enriched and purified Mn²⁺solution,and the anode solution is a dilute sulfuric acid solution.The cathode plate is made of stainless steel,and the anode plate is determined to be a titanium based ruthenium iridium plate through experimental comparison.The ion exchange membrane is a homogeneous anion exchange membrane.Using electrolysis yield,manganese recovery rate,cell voltage,and electrical energy consumption as indicators,the effects of Mn²⁺concentration,current density,electrolyte temperature,cathode p H,electrode film spacing,cathode（NH₄）₂SO₄concentration,and H₂Se O₃concentration on membrane electrolysis efficiency were investigated through single factor experiments.Subsequently,the degree of influence of different factors on electrolysis yield was determined through orthogonal experiments.The results showed that:The current density has the most significant effect on the yield of cathode electrolysis.The optimal experimental parameters ultimately determined are:Mn²⁺concentration of 40 g/L,current density of 350A/m²,electrolyte temperature of 40℃,cathode p H of 7.0,electrode film spacing of 5.5cm,cathode（NH₄）₂SO₄concentration of 100 g/L,and H₂Se O₃concentration of 0.03 g/L.Under the optimal conditions,the cathode electrolysis yield can reach 75.31%,and the manganese recovery rate is 93.75%.The manganese precipitated from the cathode has silver white metallic luster,flat and smooth surface,and the SEM image shows that the particles are uniform and dense,the particles are connected compactly,and are distributed in stepped stripes with clear layers.The XRD spectrum shows that the metal manganese crystal form precipitated from the cathode isαtype.The ICP-MS detection results show that the purity of metal manganese in one electrolysis is 99.63%.Finally,the metal manganese precipitated under the optimal parameters of the membrane electrolysis experiment was used as the raw material,crushed and sieved,and dissolved in sulfuric acid solution.The effects of solid-liquid ratio,sulfuric acid concentration,dissolution time,and reaction temperature on the dissolution effect of manganese were investigated.The optimal dissolution parameters were determined as follows:solid-liquid ratio of 60 g/L,sulfuric acid concentration of 1.5 mol/L,dissolution time of 30 min,and temperature of 50℃.At this time,the content of Mn²⁺in the solution can reach 96.7%.Using this dissolved solution as the cathode solution for secondary electrolysis,analyze the changes in the p H value of the cathode solution and the concentration of various ions in the cathode and anode solutions at different times during the electrolysis process,and explore the ion transport process and the mechanism of manganese precipitation from the cathode during the secondary electrolysis process.The experiment found that the ion transport process in the secondary electrolysis process is mainly divided into the directional migration of SO₄^2-,the concentration diffusion of H⁺,and the electroosmotic reaction of water.Afterwards,SEM and ICP-MS characterization tests were conducted on the metal manganese products precipitated by secondary electrolysis,and it was found that the manganese particles precipitated by secondary electrolysis were tightly bonded,with a large number of stepped stripes on the surface of the particles.The precipitated manganese products followed the growth mechanism of spiral dislocations.According to ICP-MS testing,the purity of secondary electrolytic manganese metal can reach 99.97%（3N）,which is 0.34%higher than that of primary electrolytic manganese.The paper uses a large amount of experimental data to recover and purify metal manganese in wastewater using the enrichment concentration membrane electrolysis recovery secondary electrolysis purification process.The application of this process not only reduces the pollution caused by manganese containing wastewater to the environment,but also effectively recycles and utilizes metal manganese resources.On this basis,the purity of manganese is improved,and the application range of metal manganese is further expanded,with significant social and economic benefits.