Preparation And Adsorption Properties Of Heavy Metal Ion Adsorbents For Electrolytic Manganese Residues

Electrolytic Manganese Residue（EMR）is a kind of acid solid waste produced in the process of producing electrolytic manganese from manganese ore,which belongs to the second class general industrial solid waste.The storage of EMR not only occupies a large amount of land,but also pollutes the surrounding water after leaching of heavy metal ions.In order to improve the comprehensive utilization rate of EMR and promote its resource utilization process.The EMR adsorbent（M-EMR）was prepared by the composite modification method of inorganic modification,ultrasonic synergism and heating assistance.The effects of M-EMR on the adsorption of Cu（Ⅱ）,Zn（Ⅱ）,As（Ⅲ）,Cd（II）,Cr（Ⅲ）,Mn（II）,Pb（II）,Ti（Ⅴ）and V（Ⅵ）were studied and the adsorption conditions were optimized;The adsorption kinetics,adsorption thermodynamics,XRD and XPS were used to reveal the possible adsorption mechanism.The experimental results showed that the EMR after washing pretreatment,when 3.0 mol/L KOH as alkali modifier,modification time was 40 min,heating temperature was 140℃,heating time was 1.0 min,the modification effect was better,the removal rate of Cu（Ⅱ）was 99.12%.The adsorption conditions of Cu（II）and Zn（II）by M-EMR were optimized.The results showed that the removal rate of Cu（II）was more than 99%when the initial concentration of Cu（Ⅱ）was 80 mg/L,the addition of M-EMR was 1.2 g/L,the adsorption time was 40 min,and the p H value of solution was 6.The removal rate of Zn（Ⅱ）was99.94%when the initial concentration of Zn（Ⅱ）was 80 mg/L,the amount of M-EMR was 1.8 g/L,the adsorption time was 20 min,and the p H value was 6.Under the same adsorption conditions,M-EMR has different adsorption effect for different heavy metal ions.V（Ⅵ）was the best adsorbent,and the removal rate was 68.33%;The second is Cd（Ⅱ）,the removal rate is 42.13%;The removal rate of As（Ⅲ）is 15.34%.By analyzing the surface morphology of EMR before and after modification,it is found that the surface of EMR after modification is broken into many small sheets,and the channels or voids are obviously increased.BET analysis shows that the modified EMR has rich pore structure.When the ratio of Epoxy Resin:Curing Agent:M-EMR was 2:1:0.2,the amount of M-EMR-P was16.28 g/L,and the p H value of solution was 7.0,the removal rate of Cu（Ⅱ）was 99.42%.The material ratio has influence on the hardness of the M-EMR-P.As the addition ratio of M-EMR increases,the hardness of the M-EMR-P decreases.Through the desorption experiment of M-EMR,it was found that the desorption effect was the best when 3%Na OH was used as desorbent and the ratio of solid to liquid was1:12.The removal rate of Cu（Ⅱ）by M-EMR after desorption reached 90.56%.The adsorption kinetics analysis showed that the adsorption process of M-EMR for heavy metal ions followed the pseudo-second-order kinetic model.The adsorption thermodynamics studies showed that△H°>0,△S°>0,△G°<0,which indicated that the adsorption process was a spontaneous endothermic reaction.The microcalorimetric analysis further proved that the adsorption process of M-EMR for heavy metal ions was an endothermic process.The results of adsorption isotherm showed that the adsorption process of M-EMR for heavy metal ions was more consistent with Langmuir adsorption model among the three isotherm models.The iron in EMR was mainly Fe S and Fe₂O₃,which was oxidized to Fe₃O₄and Fe OOH after modification.After adsorption,the form of iron was basically unchanged and relatively stable,indicating that the adsorption of heavy metal ions was caused by chemical reaction and electrostatic adsorption.The surface of M-EMR is negatively charged,while the heavy metal ions are positively charged.The adsorption of heavy metal ions is caused by electrostatic attraction and van der Waals force.Manganese in M-EMR has a great adsorption effect on Cu（II）,while hydroxyl on Fe OOH can coordinate with other metal ions such as copper ions.Therefore,the adsorption of heavy metal ions by M-EMR is a combination of chemical adsorption and physical adsorption.This study provides some theoretical guidance and data reference for the treatment of heavy metal wastewater and the resource utilization of EMR,and M-EMR has a certain industrial application prospect.