Study On Selective Precipitation,Transformation And Separation Of Molybdate And Rhenate

Molybdate and hyperrhenate often exist in molybdenite leaching solution.However,because of the similar physical and chemical properties of molybdate and hyperrhenate,there exists the co-adsorption and co-desorption behavior of Mo and Re.Therefore,the deep separation of Mo and Re is difficult.Especially,the separation and recovery effect of Mo and Re is poor in high Mo concentration and low Re concentration solution.It is very important to develop the selective and separation technology of molybdate and rhenate for the green and sustainable development of Mo industry.In this paper,the separation and recovery of Mo and Mo are successfully achieved by selective precipitation mothed and precipitation flotation mothed.Firstly,the ionic conversion behaviors of Mo-H₂O and Re-H₂O systems are studied,and the existing forms and distribution rules of Mo（Ⅵ）and Re（Ⅶ）in the mixed solution are clarified.The precipitation and separation behavior of Mo and the recovery behavior of Re by precipitation flotation during the separation of Mo and Re by selective precipitation method are studied.The chemical reaction mechanism and step separation process of Mo and Re by precipitation flotation are explored,and the regulation mechanism of selective precipitation and flotation separation of Mo and Re by selective precipitation flotation are revealed.The main conclusions of this paper are as follows:（1）Analysis of ion morphology and separation feasibility:In mixed solution,Mo（Ⅵ）hydrolyzes and exists in the forms of H₂MoO₄,HMoO₄^-,MoO₄^2-,while Re（Ⅶ）always exists in the form of ReO₄^-.What’s more,molybdatehas has strong selectivity with metal hydroxyl functional group,while rhenate has strong selectivity with amino functional group.Hence,Mo can be successfully separated from mixed solution with metal cation as precipitant.At the same time,Re can be successfully recovered from the residual liquid by using ammonium salt as precipitant.In addition,CTAB has a strong selective effect on rhenate under basic condition,while molybdate has a similar selective effect under acidic condition.So the gradual separation of Mo and Re in mixed solution can be realized by using CTAB as precipitant.（2）Behavior analysis of Mo and Re separation by selective precipitation:Metal hydroxyl compounds formed by Fe（Ⅲ）show good selectivity to Mo in mixed solution.When n（Mo）:n（Fe（Ⅲ））is 1:4 and pH value is 4,the precipitation rates of Mo and Re are 99.9%and 5.4%,respectively,and the selective separation of Mo and Re is successfully achieved.In addition,Re in the residual solution is recovered by CTAB.When the concentration of the ratio of n（Re）:n（CTAB）is 1:2,NH₄Cl is 10mg/L,the pH value is 6,and the amount of defoamer is 50 mg/L,the recovery rate of Re are 99.2%and 99.8%,respectively,with adding Al（Ⅲ）and PAM as flocculants.（3）Behavior analysis of Mo and Re separation by precipitation flotation:CTAB and DTAB can successfully separate Re from mixed solution by precipitation flotation method.When n（Re）:n（CTAB）is 1:2,n（CTAB）:n（DTAB）is 1:2 and pH value is 6,the recovery of Re and Mo are 91.6%and 4.2%,respectively.In addition,Mo can be precipitated directly by CTAB at the reaction conditions of acidity.Under the conditions of n（Mo）:n（CTAB）is 2:1,pH value is 3,foam dosage is 50μL/mL,phosphate dosage is 30 mg/L,the recovery rate of Mo is 99%.（4）Mechanism analysis with separation of Mo and Re:During the separation of Mo and Re by selective precipitation,Mo is separated from the solution by hydrolysis and dehydration reaction with metal hydroxyl compounds,while Re precipitates by electrostatic interaction and coordination with amino functional groups and NH₄⁺.During the separation of Mo and Re by precipitation flotation method,Re is separated by electrostatic interaction and coordination with amino functional groups on CTAB.And,DTAB interacts with Mo and inhibits Mo precipitation due to its strong hydrophilicity.Mo and CTAB in the residual solution are separated by chelation precipitation under the action of phosphate.