Mechanism And Properties Of Manganese Oxide Prepared By In Situ Oxidation Of Mn²⁺ With Ozone

In recent years,with the depletion of traditional resources,new energy battery industry has developed rapidly.As an important raw material of ternary battery materials,the purity of high-purity manganese sulfate will directly affect the quality of battery products,so it has far-reaching significance to realize the purification and impurity removal of manganese sulfate solution.Manganese oxides have large specific surface area,good pore structure and good adsorption potential.However,there are many kinds of manganese oxides and their crystal forms are complex.The structure and properties of many manganese oxides need further study.In this paper,the preparation of manganese oxide by ozone in-situ oxidation of manganese sulfate solution and its adsorption performance in manganese sulfate solution were studied,and a simple and economic controllable preparation method of manganese oxide and purification method of manganese sulfate solution were explored.The effects of four oxidants on the phase composition,micro morphology,element content,physical adsorption and hydroxyl group of the product were studied under weak alkaline conditions;In the process of sodium hypochlorite preparation,Cl₂would be produced and impurity sodium would be introduced;The main component of the product was Mn₃O₄and its adsorption capacity was weak;Ozone did not introduce new impurities,and the product had a high degree of oxidation.There were a lot of hydroxyl groups on the surface,which could be chemically adsorbed.The micro morphology showed that the product was formed by uniform spherical particles,with a diameter of only 50nm,rich pores,and a maximum specific surface area of 60.37m2/g.The adsorption capacity of N₂was the highest,which was better than that of sodium hypochlorite,potassium permanganate and oxygen.The effects of reaction time,pH value,temperature,Mn²⁺concentration and ozone flow rate on the morphology and physicochemical properties of manganese oxides were investigated.The results showed that the structure and properties of manganese oxides were greatly affected by pH and reaction temperature.When the solution was in weak alkaline environment,the oxidation ability of ozone was limited,so it was difficult to oxidize Mn²⁺to Mn O₂,only Mn₃O₄could be produced,With the increased of the acidity of the solution,the oxidation potential of ozone becomed higher,and Mn²⁺could be directly oxidized to Mn O₂;When the reaction temperature was 10?,the specific surface area of manganese oxide was 158.03m²/g.When the reaction temperature rised to 85?,the specific surface area of manganese oxide was41.24m²/g.The difference of specific surface area was obvious.Lower reaction temperature was conducive to obtain excellent products.The optimum conditions for the preparation of manganese oxide were as follows:reaction time was 2.5h,pH=4,reaction temperature was 10?,Mn²⁺concentration was 15g/L,ozone flow rate was 600L/h.At this time,the composition of the new manganese oxide was Mn O₂(?and?).The maximum specific surface area was183.89m²/g,the adsorption curve reaches the maximum,the particle diameter was about 20nm,the length was about 55nm,the pore was rich,the specific surface area was large,the particle was small and evenly distributed,the surface was rough and loose,and had good adsorption potential;It could provide more binding sites and better adsorption conditions for heavy metal ions in solution.Manganese oxide prepared under the above optimum conditions was used as adsorbent to study the adsorption of manganese sulfate solution.The effects of the amount of new manganese oxide,pH value of solution and adsorption time on the removal of cobalt and nickel ions were investigated.The results showed that the pH value of solution had a great influence on the removal of cobalt and nickel ions in manganese sulfate solution,and the weak acid environment was conducive to the removal of cobalt and nickel ions by manganese oxide.The adsorption process of cobalt and nickel ions was more in line with the pseudo second order kinetic equation model,and the adsorption rate was controlled by both membrane diffusion and intra particle diffusion.The results showed that the optimal adsorption conditions for removal of cobalt and nickel ions in manganese sulfate solution were as follows:the amount of manganese oxide was 1.00g,the solution pH was 6,and the adsorption time was 30min.At this time,the residual amounts of CO²⁺and Ni²⁺were 0.433mg/L and 1.063mg/L respectively,and the removal rates were 96.45%and 96.49%respectively,which met the process quality requirements of battery grade manganese sulfate HG/T 4823-2015 standard.