Extraction And Separation Of Vangandium (Ⅴ) From Aqueous Media By Temperature-induced L35/Sulfate Aqueous Two Phase System

The thermodynamic properties and the extraction and separation performance of vanadium (V) were researched by aqueous two-phase system (ATPS) composed of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) tri-block copolymer surfactant L35 and sulfate (Li2SO4/Na2SO4/MgSO4).Firstly, the thermodynamic properties were studied about the ATPS of L35/sulfate (Li2SO4/Na2SO4/MgSO4). The experimental results show that the cloud point of L35 aqueous solution decreases first and then increases with increase of L35 concentration. The cloud point of L35 falls after adding sulfate and declines gradually with increasing sulfate concentration, and the ability of reducing L35 cloud point is MgSO4>Li2SO4>Na2SO4 for three sulfate. For the L35/sulfate systems, the two-phase district area expands and the single phase district area decreases with increasing temperature. The change of pH has a little influence on two-phase district area. The liquid-liquid equilibrium data of the ATPS were correlated successfully by Othmer-Tobias and Bancroft empirical equations.Secondly, the influences of extraction conditions on extraction and separation of vanadium (V) were studied by L35/sulfate aqueous two-phase system. The experimental results indicate that the extraction rate and distribution coefficient of vanadium (V) increase first and then decreases with pH increasing. The extraction rate and distribution coefficient of vanadium (V) increase clearly after adding charge modifier octadecyl amine ethoxylate ether (1815). The extraction rate and distribution coefficient of vanadium (V) drop gradually with increasing temperature. The extraction rate and distribution coefficient of vanadium (V) are all enhance first and then maintain constant with increasing L35 and sulfate concentration. The time of extraction and equilibrium are all short. Under optimal conditions, the extraction rates of vanadium (V) of three systems were 96%,84.26% and 90.02%, respectively, and the distribution coefficients were 52.6, 8.1 and 14.8, respectively. The extraction mechanism were inferred by FT-IR and DLS. The results of separation performance of vanadium (V) with metal cations show that the efficient separation among V(V) and metal cations effectively improves after adding 1815, while the concentration of metal cations has little influence on separation performance.Finally, the stripping and precipitation performance of vanadium (V) were studied. The results demonstrate that pH has less impact on the stripping rate of vanadium (V). The stripping rate of vanadium (V) are all enhance first and then decline with increasing NH3·H2O mass fraction and temperature. The stripping rate of vanadium (V) decreases first and then increases with increasing O/A ratio. The stripping rate of vanadium (V) grows gradually and finally reaches steady with increasing stirring time and phase-separation time. Under the optimal conditions, the stripping rate of vanadium (V) is up to 98.64%. The precipitation rate of vanadium (V) increases firstly and then decreases with pH increases. The precipitation rate of vanadium (V) enhances first and then maintains constant with increasing (NH4)2SO4 mass fraction. The precipitation rate of vanadium (V) grows with increasing temperature. The stripping rate of vanadium (V) decreases first and then increases with increase of O/A ratio. Under the best conditions, the precipitation rate of vanadium (V) is up to 98.94%.