Extraction And Separation Of Tungsten(?) From Aqueous Media By TX-100-sulfate Aqueous Two Phase System

The thermodynamic properties and the extraction and separation performance of tungsten(?)in the octyl phenyl polyoxyethylene ether(TX-100)-sodium sulfate/ammonium sulfate/ lithium sulfate aqueous two-phase systems(ATPS)were systematically studied.Firstly,the thermodynamic properties of TX-100-sodium sulfate/ ammonium sulfate/lithium sulfate aqueous two-phase systems were studied.The results indicate that with increase of the temperature,the single-phase area of aqueous two-phase systems decreases and the two-phase area increases which means that phase separation ability of aqueous two-phase systems becomes strong.The phase separation ability of three different aqueous two-phase systems from strong to weak is Na2SO4>Li2SO4>(NH4)2SO4.The liquid-liquid equilibrium data were fitted by Othmer-Tobias and Bancroft empirical equations,which proves that Othmer-Tobias and Bancroft empirical equations can fit the equilibrium data correctly.Secondly,the extraction and distribution performance of tungsten(?)in the TX-100-sodium sulfate/ ammonium sulfate/ lithium sulfate aqueous two-phase systems were researched and the influence of pH value,temperature,initial W(?)concentration,sulfate concentration,TX-100 concentration,mixing time and phase separation time on the extraction performance was also explored.The results show that with the increase of pH value,the extraction rate and the distribution coefficient of W(?)decline gradually.With the increase of temperature the extraction rate of W(?)declines slightly,while the distribution coefficient of W(?)increases.With the increase of initial W(?)concentration,the extraction rate of W(?)first increases and then remains unchanged.With the increase of TX-100 concentration,both the extraction rate and the distribution coefficient of W(?)increase.With the increase of sulfate concentration,the extraction rate of W(?)declines,the distribution coefficient of W(?)in the TX-100-Li2SO4-H2 O aqueous two-phase system is increasing,but in another two aqueous two-phase systems,the distribution coefficients show decreasing trend.Mixing time and phase separation time have little influence on the extraction rate and the distribution coefficient of W(?).By theFIR and DLS tests,extraction mechanism is revealed that new substance is not formed in extracting process and polytungstate anions is transferred from salt-rich phase to TX-100-rich micellar phase depending on solubilization and electrostatic attraction.It is also proved that polytungstate anions have high hydrophobic nature so that they can be solubilized in hydrophilic outer shell of TX-100 micelles by electrostatic attraction.Finally,the stripping and separation performance of W(?)were researched.The results indicate that with the increase of pH value,phase ratio value,temperature and ammonium sulfate concentration,the stripping percentage of W(?)increases.When W(?)is separated from Fe(III),Cu(II),Ni(II),Co(II),Mn(II),Cr(III),Al(III),Zn(III),it can be seen that as the increase of metal cations concentration,the extraction rate of W(?)is always very high and the extraction rates of other metal cations remain relatively low,which demonstrates that TX-100-sodium sulfate-H2 O aqueous two-phase system can achieve the goal of separating W(?)from other metal cations successfully.