| As a important strategic resources,more than 88%of vanadium and it's products in our country is produced by using vanadium slag as raw material.On account of the high energy consumption?high cost and the emission of harmful gases during the process of traditional V extraction technology,our group proposed directly pressure of vanadium slag leaching by waste titanium dioxide without roasting.This paper take the acid leach solution of vanadium slag above-mentioned as the main project of stuy,the chemical composition,existent state of elements,forms of vanadium ion and iron ion in the leach solution was analysised.And experiments of V4+?V5+ extraction,separation between V4+ and Fe3+ was carried out meanwhile tetravalent vanadium extraction mechanism was also explained.(1)E-pH diagrams of V-Ti-H2O system,V-Mn-H2O system,V-Cr-H2O system,V-Al-H2O system and V-Fe-H2O system of the leaching system were obtained through thermodynamics calculation,which revealed that in the relevant acid leaching condition,soluble vanadium in the acid leaching system mainly exist in the form of VO2+,VO2+ or V3+?V02+,which with Fe3+,Mn2+,Fe2+,Cr2+ and Al3+stabilized leaching together.(2)When the leachate pH = 2,standard addition method is used which indirectly obtain that V4+ concentration is 0.238 mol/L(12.124g/L),V 5+concentration is 0.017 mol/L(0.866 g/L),Fe2+concentration is 0.452 mol/L(25.312 g/L),Fe3+ concentration of 0.585(32.760 g/L)in the leachate.It can be known that tetravalent vanadium mainly exists in the form of VO2+,pentavalent vanadium mainly exists in the form of V02+ by drawing component advantage area diagram of V-H2O and Fe-H2O.(3)Using P204 as extraction agent,this paper make research on the P204 extraction performance for V4+ and reaction mecnanism,the result show that under optimal extraction condition:pH=2.2,phase ration(O/A)=3:1,reaction time 6 min in the 25%P204-75%sulfonated kerosene extraction system,single-stage extraction rate of V4+ can reach 91.36%.when the V4+ concentration of 10 g/L,P204 dosage is 25%,the extraction equilibrium equation can be expressed as VO(a)2++1.5H2A2(o)(?)VOA2·HA(o)+2H(a)+,or an average of three P204 molecules combine with a VO2+ ions.(4)The comparison of P204 extraction performance for V4+ and V5+ shows the extraction performance of V4+ is better than V5+,under optimal extraction condition:pH=2.4,phase ration(O/A)=1:1,reaction time 8 min in the 20%P204-80%sulfonated kerosene extraction system,the single-stage extraction rate of V5+ is 88.41%,and for the same concentratio and experiment condition,the extraction rate of V4+ can reach 96.39%(5)From the result of separation experiment between V4+(10g/L)and Fe3+(30g/L),the optimal separation condition is obtained as:T=30?,pH=1.6,phase ration(O/A)=1:1,reaction time 8 min,dosage of reductant Na2SO3 0.4 Fe.Under the optimal exerimntcondition,the extraction rate of V is 79.39%and the extraction rate of Fe is 18.72%.According to the vanadium iron separation of orthogonal test and single factor test results,multilevel cross-flow extraction stage can be calculated to be 3 and then vanadium overall yield was 98.17%,iron total yield of 29.13%,vanadium iron separation factor of 126.7,eventually achieve a perfect separation effect between vanadium and iron. |
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