Study On Extraction Separation Characteristics Of Scandium From High Acid And High Iron Solution

Due to the high energy consumption,high cost and the emission of harmful gases in traditional vanadium extraction technology,a new technology of extraction of vanadium from converter vanadium slag by high pressure acid leaching without roasting was proposed by our team.In this paper,the research of extraction separating scandium from the acid]eaching solution was carried out.First of all,for the preparation of high acid and high iron containing scandium solution was basic studied scandium extraction separation of iron,focuses on the selection of extraction agent,extraction,washing and stripping process,the optimal process conditions;then,based on the study of the actual extraction separation in leaching solution of scandium and other elements the new technology industrialization so as to provide a necessary theoretical basis for implementation;and the extraction mechanism was investigated.The main contents of this paper were listed as follows:1)Chemical state analysis of high acid and high iron containing scandium solutionIt is known that,soluble Sc in solution mainly exists in the form of Sc3+,ScSO4+ and so on.The stable existence of soluble Sc is Fe3+,Fe(SO4)+,Fe(SO4)2-,and HSO4-plasma from draw the potential-pH diagrams of S-H2O,Fe-S-H2O,Sc-S-H2O and concentration fraction-pH diagrams of Fe and Sc were drawn in water solution.2)Extraction separation of scandium and iron in a simulated mixture of high acid and high iron in scandium containing solutiona.The extraction separation was carried out in synthetic solution according to the composition of leaching solution.The best conditions of extraction as follows:at room temperature,the initial pH of solution of-0.4,composition of organic pHase of 8%P204+2%TBP+90%sulfonated kerosene,ratio of phase(O/A)of 1:10,rotating time of 5 min.Under these conditions,the single stage extraction rate of scandium and iron were 94.02%and 1%,respectively.The extraction rate of scandium could reach 99.72%with two stages countercurrent extraction,but only 4.05%of iron was extracted.b.Scrubbing of iron from loaded organic phase was studied.The best conditions were shown as follows:hydrochloric acid was choose as washing agent,at room temperature,concetration of HCl is 4 mol/L,ration of phase(O/A)is 2:1,rotating time is 5 min.Under those conditions,single stage scrubbing rate of iron is 89.56%,however,scandium was hardly to be removed.Four stage flow scrubbing and three stage countercurrent scrubbing were studied,results shows the scrubbing rates of iron were 99.94%and 98.67%respectively,with only 0.1%of scandium of both.c.Stripping of Sc from organic phase was studied.NaOH and NaCl were selected as stripping agent,under the conditions of 40?,2 mol/L NaOH and 1 mol/L NaCl,the ratio(O/A)is 1:1,rotating time is 30 min.The stripping rate of single stage is 78.69%,85%of scandium was stripped by three flow stripping.The reason that scandium cannot be stripped thoroughly may be the secondary extraction of scandium ion in organic phase,again,by forming complex or aquo-complex with OH-or H2O.3)Extraction separation of Scandium from strong acidic liquid of Vanadium slag leached by waste acid of titanium dioxide:a.The extraction separation in leaching solution.The best conditions of extraction as follows:at room temperature,the initial pH of solution is-0.75,composition of organic phase is 10%P204+2%TBP+88%sulfonated kerosene,ratio of phase(O/A)is 1:10,rotating time of 5min.Under these conditions,the single stage extraction rate of scandium were 93.3%,the extraction rate of Fe,V,Mn,Mg,Al and Cr is less than 5%,and the extraction rate of Ti is 9.7%.The separation of Scandium with other valuable elements and impurities can be achieved.b.The optimal washing conditions of pure solution experiments on the load organic phase:4mol/LHCl,O/A=1:10,washing time is 5min,washing results of the elements:the elution rate of Sc is 1.1%,and the elution rates of Fe,Mn,Ti,Al and Mg are all above 95%,the elution rate of V is 80%,and Cr is 85.6%.c.The organic phase stripping experiment using optimal stripping conditions of pure solution:2mol/LNaOH+1mol/LNaCl,O/A=1:1 time is 30min,temperature is 40?,the result of elements stripping:the stripping rate of Sc reached 87.2%,the stripping rate of Fe and V was 13.8%,10.3%,and the other elements were 0.4)Extraction mechanism was studiedThe ratio of extraction agent to scandium is about 2,which was determined by determining saturated capacity and slop method.It is found that the extraction mechanism was changed by experimental analysis and FT-IR analysis under the condition of different pH.The results show that cation exchange mechanism plays an important role at high value of pH,however,solvation plays an important role at low value of pH.