Experimental Study Of Vanadium Extraction From The Acid Leaching Solution Containing Vanadium Steel Slag

The method of solvent extraction and the method of ion exchange are researched most to recover vanadium from acid extract. These two methods can both play two roles in the process of the recovery of vanadium from the vanadium-bearing solution. Firstly, the low concentrations of vanadium have been enriched from several grams per liter to the enrichment of a few dozen grams per liter, which is conducive to precipitate vanadium and increase the recovery rate of precipitated vanadium. Secondly, the vanadium and the impurities in the extract have been separated, which replaces the purification process, and reduce the cost of purification. There exist advantages and disadvantages in both methods. Generally speaking, the method of extraction is more suitable for recovering valuable metals from the acidic solution, and it makes vanadium and most of the impurities in the leaching solution separate, which replaces the purification process.The liquid raw materials of the test is the acid leaching solution from re-election concentrate for the converter containing vanadium steel slag. The main impurity element in the steel slag acid extract is iron whose form is mainly Fe3+ and Fe2+. The primary purpose for the purification is to remove iron. FeCl3 cannot be hydrolyzed to remove iron when its pH is between 1.5 and 2.3. Because when the iron is precipitated, the vanadium is also precipitated. Therefore, the method of extraction can be used to extract to purify, remove iron and extract vanadium and the process is extracting- washing- stripping.Aiming to the peculiarity of the steel slag acid extract containing vanadium, an experimental study has been made to prove the feasibility of the method of extracting vanadium from five aspects as follows:(1) The results can be got from the comparative tests of the extraction of N235 and P204 in different conditions. The effect of the extraction test with the main extractant N235 is better and the extraction rate and the stability of vanadium are relatively higher;(2) The results can be got from the selective tests in different pretreatment ways. The pretreatment speed of oxidant H2O2 is faster and the processing cycle is shorter and the cost is lower;(3) It is essential to use synergic reagent TBP in order to make the phase clear in the process of extraction of vanadium. The N235 and TBP sulphonated kerosene system is adopted for sure and the multilevel extraction must be adopted to increase the extraction efficiency.(4) It is essential to wash the load organic phase before stripping, because the load organic phase removed the majority of impurities after washing, and provided a qualified load organic phase for stripping, which directly compared to the stripping with no washing; after washing the stripping rate reached over 99%, and it did not appear muddy or precipitable phenomenon in the process of stripping.(5) The studies of N235 extraction mechanism show that the stripping is relatively easier when the process of the ion exchange for N235 extracting HV10O285- compared to the primary amine and the secondary amine of the coordination mechanism extraction.It is recommended in the test to use the techniques of six level extraction-three level washing-one level stripping. The extraction system is the sulfonated kerosene solution with 10%N235+5%TBP, when which acidity adjusting to pH=1.50, after H2O2 oxidation pretreating, the extraction rate can reach to 98%; the washing solution is the solution 0.50mol/L Na2SO4, which removed the impurities in the load organic phase, such as Fe and the loss rate of vanadium can reach to below 0.5%; the solution 0.70 mol/L Na2CO3 is used as the stripping agent and the stripping rate can reach to 99%.After the process of extracting- washing- stripping, not only vanadium enriches from 2.23g/L to 17.14g/L, but also most of the impurities are separated and Fe2+, Ca2+ and Mg2+ are almost removed. This solution can directly be used to deposit vanadium. The depositing vanadium about the stripping fluid of steel slag is held and the depositing vanadium rate can reach to over 98%. The products of refined vanadium are up to the national standards.