High-efficient and selective extraction of vanadium (V) with N235-P507 synergistic extraction system

A high-efficient and selective extraction method for recovering vanadium (V) was proposed using the mixed extractant consisting of N235 and P507. Various common synergistic extractants on vanadium (V) extraction was investigated and P507 was selected as the effective synergistic extractant in the N235-based extraction system according to the synergistic effect and the extraction efficiency. The effects of extractant mixture composition on vanadium extraction efficiency and synergistic coefficient were studied when the extractant concentration kept 20% (v/v). The results showed the maximum synergistic coefficient 1.42 and extraction efficiency 89.36% were attained by adjusting volume ratio to 8: 12 (N235: P507). According to the slope method and FT-IR spectra analysis, the hydrogen bond between N235 and P507 (NH⋯OP) was produced after mixing N235 and P507, which leaded the broken of P507 dimer and a higher extraction efficiency, and (VO2A·R3NH+)2SO42− was formed through a cation exchange mechanism. Acid leaching solution obtained from stone coal was used to test the selectivity of the synergistic extraction system. The separation factors of mixed extractant for vanadium with other impurities had obvious improvement compared with the single N235 or P507. More than 95% vanadium was extracted and most of impurities stayed in the feed after one stage extraction using 8 vol.% N235 and 12 vol.% P507 mixed extractant under the following conditions: initial pH of 1.70, contact time of 10 min, temperature of 25 °C, and phase ratio (O/A) of 1: 2.