Process to separate the vanadium contained in inorganic acid solutions

Abstract

A process for recovering vanadium contained in inorganic acid solutions by precipitating the vanadium as a solid compound of vanadium and alkali metal or monovalent cation ferricyanide. Separation is carried out electrochemically by depositing the compound on to a metal immersed in the acid solution that contains vanadium, to which a ferricyanide salt of an alkali metal or a monovalent cation has been added. If the inorganic acid present in solution is different from nitric acid, the vanadium can be also separated by direct addition of a ferricyanide salt of an alkali metal or a monovalent cation to the acid solution containing vanadium. The method described allows recovery of vanadium without modifying the initial composition of the solution, except for the concentration of the vanadium dissolved.

What is meant to be protected is:  
     
         1 . A process that separates the vanadium contained in inorganic acid solutions which consist in: 
 a. Adding a ferricyanide salt (hexacyanoferrate (III)) of alkaline metal or monovalent cation to the acid solution, in a proportion determined by the quantity of dissolved and to be recovered vanadium, in a minimal relation of at least two moles of iron in the salt for each three moles of vanadium contained in solution. It is also possible to add an excess of iron compound without affecting the percentage of recovery.    b. Electrodepositing a solid compound of vanadyl and alkaline metal or monovalent cation ferrocyanide on a piece of conducting material immersed in the solution described in ‘a’.    c. Electrodeposition is done applying a cathodic current density higher than 0.52 mA/cm 2 , or a constant potential more negative than 0.85 V with respect to the saturated calomel electrode, to a piece of conducting material.    d. The electrodeposition charge described in ‘b’ and ‘c’ is determined by the quantity of vanadium dissolved in the solution described in ‘a’ using the following relation: 36.8 C/cm 2  for each vanadium gram to be recovered.    e. The solid builds up on the piece of conducting material and eventually, by the effects of gravity, detaches from the conducting material and remains suspended in solution. Then the solid suspended in the solution is separated with some physical method like filtration or centrifugation. Because of its low adherence, the material that has deposited over the conducting material is recovered by softly scraping the surface.    
     
     
         2 . A process that recovers vanadium dissolved in solutions or liquors of sulfuric acid which consists in: 
 a. Adding a ferrocyanide salt (hexacyanoferrate (II)) of alkaline metal or monovalent cation to the acid solution or liquor that contains dissolved vanadium, in a proportion determined by the quantity of dissolved vanadium, and with a minimal relation of at least two moles of iron contained in the salt for each three moles of vanadium in solution. It is also possible to add an excess of the iron compound without affecting the percentage of recovery.    b. Separating from solution or liquor the solid formed in the numeral ‘ 2   a ’, vanadyl and alkaline metal or monovalent cation ferrocyanide, by means of a physical method such as filtration, centrifugation, decantation, etc.    
     
     
         3 . A process according to claims ‘ 1 ’ and ‘ 2 ,’ where the acid solution comes from the processing of a carbonaceous material.  
     
     
         4 . A process according to claims ‘ 1 ’ and ‘ 2 ’, where the carbonaceous material described in claim ‘ 3 ’ can be: crude oil and its fractions or residues originated from refining processes or treatments of crude oil, cokes, mineral coal and bitumen sands.  
     
     
         5 . A process according to claims ‘ 1 ’ and ‘ 2 ’ where the acid solution can be concentrated or dilute.  
     
     
         6 . A process that according to claim ‘ 1 ’ where the acid solution is selected among the following group of acids: sulfuric, nitric, perchloric, hydrochloric, phosphoric and hydrofluoric or a mixture of them.