Leaching Vanadium From Petroleum Coke By Alkali Solution And The Structure Of Vanadium In Alkali Leaching Liquid

Petroleum coke is the main raw material to produce carbon anode. The quality of carbon anode is closely related to the electrolytic aluminium efficiency and yield.At present, most of the petroleum coke contains excessive levels of vanadium at home and abroad. The carbon anode made by high vanadium petroleum coke will produces excessive consumption which influence the electrolytic aluminium efficiency seriously. A new process of extraction vanadium from high vanadium petroleum coke by alkali was investigated. And the structure of leaching liquid was analyzed multiplicity. Provided a theoretical basis for optimizing vanadium leaching processes.In the experiment, the high vanadium petroleum coke is adopted from a factory in Shandong province. In the early stage, the preliminary exploration of vanadium leaching from high vanadium petroleum coke under ambient temperature and atmospheric pressure was done. And on this basis The vanadium petroleum leaching by tank,column and heap-leaching tests were done. The influence of major factors in tank-leaching were studied, and the optimal conditions were: temperature of 110 ℃;liquid-solid of 6:1; the NaOH concentration is 150g/L. The leaching efficiency can reach67.89%. The results compared with early test have been significantly increased. Different concentrations in the column-leaching were done. When the NaOH concentration is75g/L, the leaching efficiency can reach 53.76%. Heap-leaching rate can reach 47.97%under 75g/L of the NaOH concentration.In the second stage, the infrared spectrum of the pure solution system of NaOH-V2O5 was analyzed. The ion structures was determined in the solution. And make sure that as the conditions change, the changing of ion structures. The infrared spectrogram of vanadium leachate from petroleum coke was studied under different conditions. The change of vanadium acid radical ions in leachate was analyzed, and the three kinds of vanadate ions can be transformed while leaching condition was changed.When the leaching time was prolonged, the ion of vanadium dimer acid radical ions was formed to V-O chemical bond by depolymerization; when the leaching temperature increased, the ion of vanadium dimer V-O-V was exploded to V-O and V-OH chemical bond; when the leaching environment was under medium and low NaOH concentration, the V-OH was partly turned to vanadium dimer acid radical ions and V-O when the leaching environment was under high NaOH concentration, the leaching rate did not change essentially, and the ions remained unchanged. The ions changing ruleswere further verified through the Raman spectrum of leachate under different NaOH concentrations which further validated the changes of ion structures.In the last stage, the influence of impurity element-S on the petroleum coke leaching was done. Assessing the relationship between the sodium sulfate and sodium vanadate solution, thus analysis inhibitory effects of impurities on the petroleum coke extracts which relies on the relationship between the viscosity, conductivity, contact angle and surface tension with the leaching rate in petroleum coke leach liquor. Results show that with the increasing of sodium sulfate amount, the leaching rate rising firstly and then declining. At this point, the viscosity is just opposite with it. In addition, the change of conductivity is rising firstly, then downing and rising at last in the same condition. But the surface tension is first decrease and then remain unchanged, at last present a increasing trend. The changing of contact angle have approximately the same with leaching rate. The main reason produced the above phenomenon is : the low sodium ion concentration promoting effect to the leaching reaction, which accelerate the reaction rate, and then increasing the leaching rate. When the concentration of sodium ion increased, the ion of V(OH)6- dehydration condensation into V2(OH)102- because of the sodium ion hydration.Then ionic radius increases which cause the increasing of solution conductivity and viscosity. Affecting the leaching reaction. At the same time, the presence of high sodium ions concentration make the sodium transform into vanadium radical is low. The surface tension and contact angle increased which inhibits the reaction between pentavalent vanadium ion and sodium hydroxide. Then the leaching rate reduces.