Study On The Recovery Of Manganese In Wastewater And Membrane Refining Technology

Manganese is an important metal element with high strategic value,which is widely used in steel manufacturing,battery manufacturing,chemical industry,medicine,environmental protection and other fields.A large amount of manganese containing wastewater is generated during the production of manganese,and effective wastewater treatment measures are needed to reduce its impact on the environment and human beings.Compared with the traditional chemical precipitation or biological treatment technologies,which have problems of incomplete pollution control,high treatment cost and waste of resources,this study designs the"ion exchange enrichment+single membrane double chamber electrolysis recovery"process for manganese wastewater with high manganese ion content but not enough to reach the optimal concentration standard for membrane refining and recovery.With the use of membrane refining technology,the quality of recovered manganese products is improved,and the enrichment of sulfuric acid can be achieved in the anode chamber,which maximizes the recycling of resources while treating heavy metal wastewater.Firstly,the optimal process parameters of ion exchange resin enrichment for Mn²⁺containing wastewater were investigated.The Mn²⁺enrichment was carried out by using the downward inlet and upward outlet feeding direction for Mn-containing wastewater,and the resin was regenerated by using the upward inlet and downward outlet feeding direction for dilute sulfuric acid.The results showed that the adsorption rate of Mn²⁺was as high as 99.7%under the conditions of initial pH value of 4,inlet liquid speed of 6m/h,resin height of 70cm and adsorption time of 180min.Then,530ml of 8%sulfuric acid was used to elute the Mn²⁺,and the regeneration liquid feed rate was controlled to be 2.5m/h.The enriched Mn²⁺concentration could reach 14.48g/L,and the elution efficiency was as high as 99.6%,and the enrichment multiplier could reach 26 times,which realized the enrichment of Mn²⁺.Subsequently,the membrane refining technology was used to recover the wastewater containing manganese in high concentration.The enriched Mn²⁺solution was used as the cathode solution,H₂SO₄as the anode solution and stainless steel plate as the cathode,and the TRJAM-10W type homogeneous membrane for the anion exchange membrane and the titanium-based iridium-tantalum plate for the anode were determined by preferential selection.The results showed that the Mn²⁺concentration was 40g/L,the cathode current density was400A/m²,the anode current density was 800A/m²,the cathode liquid（NH₄）₂SO₄concentration was 80g/L,the cathode liquid H₂SeO₃concentration was 0.03g/L,the initial pH value of the cathode was 7.5;the anode liquid H₂SO₄concentration was 0.5mol/L;the spacing between the electrodes was 50mm The electrolysis temperature is 40℃.Under these conditions,the current efficiency can be maintained at about 75%,acid recovery at about 64%,manganese recovery at about 92%,voltage at about 5.9V,and power consumption at about7400k W·h/t.Finally,the experimental analysis shows that the ion transport in the membrane refining process is dominated by electrochemical polarization and ion migration,accompanied by a certain degree of differential concentration polarization.In the cathode chamber,Mn²⁺and free ammonia are adsorbed on the surface of the electrode plate through the formation of manganese ammonia complex ions,which are then reduced to manganese monomers to desorb free ammonia for deposition on the surface of the electrode plate.In addition,there is hydrogen precipitation reaction in the cathode chamber,and the generated OH^-will increase the pH of the cathode liquid;the oxygen precipitation reaction will occur in the anode chamber,and the generated H⁺and the migrated SO₄^2-will form H₂SO₄to realize the enrichment of sulfuric acid.SEM,XRD,EDS and ICP-OES analyses of the manganese recovered under the optimal parameters showed a uniform microscopic stacking of layers with tight crystalline connections and a crystal growth trend in accordance with a spiral dislocation mechanism;the manganese obtained by electrolysis was a body-centered cubicα-type manganese;the elements contained on the surface were pure manganese;and the overall purity could reach 99.81%.In addition,the treatment of each ton of wastewater can create an economic benefit of 4.43 yuan.The paper verifies the feasibility of recovering manganese from manganese containing wastewater through enrichment-membrane refining process by comparing a large amount of experimental data and analyzing the experimental mechanism.This process is a manganese recovery process that is both environmental friendly,energy saving and economic,which is in line with the development of the times and provides theoretical support and new ideas for the research of manganese containing wastewater and heavy metal wastewater treatment.