The Ions Behavior And Thermodynamics Analysis Of Solution System During Leaching Processing Of Roasted Stone Coal

The leaching process is key link in vanadium extraction from stone coal.While a large number of impurity ions such as Fe and Al would also enter in the solution when the vanadium was leached,which affect the subsequent purification enrichment and vanadium precipitation process.Finding out the ion behaviour of vanadium,iron,aluminum during leaching process and the main ions existence form in leaching solution were of great significance for the optimization of leaching solution treatment technology.This thesis researched the leaching behaviour of vanadium,iron and aluminum during acid leaching process by using decarburization sample of stone coal from Hubei province on the basis of determining the optimum leaching system and combining thermodynamics method.Calculating and analyzing the existence form of V,Fe,Al in acid leaching solution.As the results showed during the acid leaching processing the vanadium leaching efficiency was 81.05%,at the same time the iron and aluminum leaching efficiency were 42.74% and 85.44%.Through the thermodynamics analysis in the calcium fluoride and sulfuric acid leaching system when the main vanadium-bearing mineral muscovite was dissolved the potassium feldspar and hematite would also be dissolved.The effects of sulfuric acid concentration,leaching temperature,leaching time,and liquid/solid ratio on vanadium,iron,and aluminum leaching efficiency have the same trend.And the leaching efficiency of aluminum is higher than that of vanadium and iron.During the vanadium extraction from stone coal decarburization sample the sequences of leaching difficult degree of the main minerals were obtained as follows: hematite,muscovite,potassium feldspar.Hematite needs a long time to reach the dissolution balance.So the leaching time can be shorten appropriately on the premise of vanadium leaching efficiency so as to decrease the iron leaching as far as possible.Using the ion concentration in acid leaching solution obtained under the optimum experimental condition as a benchmark.Analyzing the thermodynamic equilibrium distibution vary with p H value of the existence form of vanadium,iron,and aluminum in sulfuric acid solution system,sulfate solution containing fluorine ion system,and acid leaching solution system.The results showed that the fluorine ion and sulfate ion have great influence on the existence form of vanadium,iron,and aluminum.In this acid leaching solution the vanadium existed in the forms of VO²⁺ and VOSO₄,the ferrous iron existed in the forms of Fe²⁺ and FeSO₄,the iron existed in the forms of FeSO₄⁺ and Fe?SO₄?₂^-,the aluminum existed in the forms of AlF²⁺?AlF₂⁺?AlSO₄⁺ and Al?SO₄?₂^-.The fluoride ion would not cause the existence form of vanadium ion complex to affect the extraction process,due to the iron and aluminum ions have the priority of complexation with fluorine ion.The determination of different ion components and existence forms in acid leaching solution have a certain guilding role in optimizing subsequent purification enrichment and vanadium precipitation process.