Extraction And Separation Of Vanadium From Aqueous Media By Polyethylene Glycol-Sodium Sulfate Aqueous Two-phase System

The extraction and stripping,separation with associated cations and extraction mechanism of vanadium were studied by aqueous two-phase systems composed of polyethylene glycol 2000?PEG2000?and sulfate.The purpose is to provide theoretical guidance for future industrial application.First,the phase equilibria of PEG2000-Na₂SO₄ aqueous two-phase system were studied and the effect of system constitute and temperature on the phase equilibria performance.The results indicated that the difference in two phases increases,the area in two phases district enlarges and the ability of phase separation becomes stronger with increasing system constitute and temperature.The phase equilibrium data were correlated by Othmer-Tobias and Bancroft empirical equations,and the correlation accuracy is high.Second,the extraction of vanadium was carried out with PEG2000-Na₂SO₄ aqueous two-phase system.The effects of pH value,charge modifier type and concentration,initial vanadium concentration,different temperature and salt type and concentration on vanadium extraction were researched.The experimental results showed that the aqueous pH value and charge modifier are important factors affecting the extraction performance of vanadium.The effect of type of charge modifier on the extraction of vanadium is little.The extraction rate and partition coefficient of vanadium decreases with increasing temperature,showing that the extraction of vanadium is exothermal.The effect of lithium sulfate,sodium sulfate and magnesium sulfate on the extraction of vanadium is lesser and higher extraction rate was obtained,but the extraction rate of vanadium decreases significantly after adding sodium chloride and sodium nitrate in aqueous two-phase systems.The extraction mechanism analysis revealed that polyvanadate anion is extracted into PEG 2000-rich phase due to the electrostatic attraction between protonated charge modifier and polyvanadate anion by the change of the initial and equilibrium pH in aqueous phase,Fourier Transform Infrared Spectroscopy?FT-IR?and Dynamic Light Scattering?DLS?.Third,the separation performance between vanadium and metal cations(?Fe?III?,Co?II?,Ni?II?,Cu?II?,Zn?II?,Al?III?,Cr?III?,Mn?II??under various concentrations was studied under the optimal extraction conditions of vanadium.The results indicated that the extraction rate of vanadium has no obvious change with the increase of metal ion concentration,but increases with increasing 1815 concentration.At the same time,the extraction rate of metal cations tends to decrease gradually and is below 10%,which showed that efficient separation of vanadium and metal cations realizes.Last,the effect of stripping performance on ammonium carbonate concentration,temperature,phase ratio,stirring and aging time,et al was studied for PEG2000-rich phase loaded vanadium.The experimental results showed that the stripping rate of vanadium increases with the increase of ammonium carbonate concentration and temperature.The precipitation rate of vanadium decreases with increasing ammonium carbonate concentration,temperature and phase ratio,however,the precipitation rate of vanadium increases as increasing aging time.The effect of stirring time on the stipping and precipitation of vanadium is little.