Solvent Extraction Of Vanadium From The Leachate Of Stone Coal With N235

Nowadays, the acid leaching and P204 extracting is a common technology for extracting vanadium from stone coal. This technology needs to adjust the pH value of leachate to 2 by lime and restore the leachate before extraction, and it also needs to oxidize the stripping liquid after extraction. The process is complex, high-cost, and it is difficult to separate solid and liquid after adjusting the pH value. What's worse, it is hard to separate the main impurities from leachate completely since P204 is a kind of cationic extraction agent. In order to simplify the process flow and reduce the cost, we propose to use N235 to extract the vanadium from leaching solution of stone coal in condition of low pH value, and recycle vanadium.The study investigates the ability of N235 to extract the main impurities. The result shows that in the same condition, N235 is more suitable for extracting V(V) than V(?). High pH value contributes to the extraction of V(V). The extraction rate reaches to 97.21% when the pH value is 1. When pH value varies from 0 to 2, Fe2+, Al3+, Mg2+, PO43-and Si2O32- can be extracted weakly by N235, and the extraction rate of Fe3+ markedly decrease when the pH is under 1.5. Overall, Fe3+, Al3+, Mg2+, PO43-and Si2O32- have barely influence on vanadium extraction.The study indicates the extraction parameters from leaching solution by amine extractant N235. The total extraction rate of vanadium after 2-stage extraction is 97.82% under conditions of the volume fraction of N235 is 40%, and the ratio of organic phase to water is 1:4, and the extraction time is 6min at 25?;The total washing rate of sulfuric acid after 2-stage washing is 52.5%,under conditions of the ratio of organic phase to water is 1:1, and the washing time is 10 min at 55?; The total extraction rate of vanadium after 2-stage stripping is more than 99% under conditions of the concentration of Na2CO3 as stripping agent is 0.8mol/L, and the ratio of organic phase to water is 3:1, and the extraction time is 6min at 25?. Vanadium can be separated effectively from major impurities after extraction. The main impurities, such as iron, aluminum, calcium, magnesium, have been removed more than 95%. According to the result of infrared spectrum analysis, the organic phase after stripping is similar to the organic phase before extraction on the characteristic peaks of infrared spectrum, and it means that the N235 extractant after stripping can be recycled.The paper also discusses the mechanism of vanadium extraction by N235. The results of the saturation method and the slop method indicate that the composition of extraction is [R3NH]4[H2V10O28]. The equilibrium constant of extraction reaction is 195.434 mol-1·L·s-1. And in the reaction systerm, H is-10.683 kJ/mol, G is-13.076 kJ/mol, S is 8.032 J/(mol·K). Therefore the reaction is exothermic reaction, and rising the temperature goes against the reaction. The G is under 0, thus the reaction is easy to occur and can occur spontaneously.