EXTRACTION OF MOLYBDENUM AND VANADIUM FROM HYDROCHLORIC ACID BY TRI-n-BUTYL PHOSPHATE IN VARIOUS DILUENT SOLUTIONS

Abstract

The mechanism of extraction was studied, employing several diluents with differing electron-accepting properties. For molybdenum, from 3-7 mol/l acid, the following formulation holds for all diluents and over the whole range of loading ratio of TBP.
2TBP+MoO₂²⁺+2CL^-=(TBP)₂MoO₂CL₂ K_ex
The extraction constants are 4.42 for n-heptane, 1.50 for xylene and 0.0114 for chloroform at low loading. They start to decrease sharply at medium and high loading. This is caused by the variation of properties of the organic solution due to the presence of the excessive amount of organic molybdenum.
For vanadium, from 2-5 mol/l acid, the following formulations hold in the range observed.
4TBP+VO²⁺+H⁺+3CL^-=(TBP)₄VO(HCL)CL₂ K_ex.1
4TBP+VO²+2CL^-=(TBP)₄VOCL₂ K_ex.2
The constants are K_{ex, 1} = 1.41 × 10^-5 and K_{ex, 2}=9.19 × 10^-5 in xylene diluent. They remain constant in the range of normal operation, since the extractability of TBP for this metal is very low.