This invention relates to a process for the recovery of cobalt ions and tungstic acid and/or its derivatives from aqueous solutions, such as in particular the spent catalytic waters deriving from processes for the oxidative cleavage of vegetable oils. In particular this invention relates to a process for the recovery of cobalt ions and tungstic acid and/or its derivatives which provides for the use of cation-exchange resins.

The present invention relates to a method for recovering vanadium and tungsten from a leach solution of a waste denitrification catalyst, and more specifically, to a method for recovering vanadium and tungsten from a leach solution of a waste denitrification catalyst comprising the steps of: recovering vanadium by adding acid and then adding a calcium compound to a leach solution of a waste denitrification catalyst to precipitate the vanadium; and recovering tungsten by adding acid and then adding a calcium compound to the remaining leach solution after recovering the vanadium to precipitate the tungsten.

The present invention provides a method for selective recovery of a valuable metal from a waste denitrification catalyst through alkali fusion, the method comprising the steps of: (a) adding an alkali metal to a waste denitrification catalyst, followed by mixing and alkali fusion, to generate a calcination product; (b) subjecting the calcination product to water-leaching to recover an alkali leachate and a residue; (c) adding a precipitator to the alkali leachate, followed by stirring, to recover calcium metavanadate (Ca(VO.sub.3).sub.2) or calcium tungstate (CaWO.sub.4) through precipitation; and (d) subjecting the recovered calcium tungstate to acid decomposition to prepare tungstic acid. Therefore, vanadium and tungsten can be recovered at high efficiency by a method in which a precipitator is added to a leachate, which is obtained by adding an excess amount of an alkali metal to a waste denitrification catalyst and carrying out calcination and water-leaching, and then a reaction rate is controlled.

This invention relates to a process for the recovery of cobalt ions and tungstic acid and/or its derivatives from aqueous solutions, such as in particular the spent catalytic waters deriving from processes for the oxidative cleavage of vegetable oils. In particular this invention relates to a process for the recovery of cobalt ions and tungstic acid and/or its derivatives which provides for the use of cation-exchange resins.

Methods of isolating tungsten and, in particular, methods of separating tungsten and vanadium are described herein. The methods can generally comprise treating a tungsten-containing material in aqueous solution with a reducing agent suitable for the reduction of pentavalent vanadium to one or more lower oxidation states of vanadium, such that the tungsten can be more readily separated from the vanadium, e.g., via solvent extraction. In certain embodiments, the methods disclosed herein can provide tungsten, vanadium, or both tungsten and vanadium in sufficient purities for commercial use.

Disclosed is a method for effectively leaching valuable metals such as vanadium and tungsten contained in a waste denitrification catalyst by using roasting and water leaching. According to the present invention, the method for leaching valuable metals contained in a waste denitrification catalyst comprises the steps of: (a) mixing a waste denitrification catalyst containing vanadium (V) and tungsten (W) in the form of an oxide with an alkali metal compound to form a mixture; (b) roasting the mixture to generate a roasting product comprising sodium vanadate (NaVO.sub.3) and sodium tungstate (Na.sub.2WO.sub.4); and (c) injecting the roasting product into water to water leach sodium vanadate and sodium tungstate in the form of a vanadate ion (VO.sub.3.sup.) and a tungstate ion (WO.sub.4.sup.2).

Methods of isolating tungsten and, in particular, methods of separating tungsten and vanadium are described herein. The methods can generally comprise treating a tungsten-containing material in aqueous solution with a reducing agent suitable for the reduction of pentavalent vanadium to one or more lower oxidation states of vanadium, such that the tungsten can be more readily separated from the vanadium, e.g., via solvent extraction. In certain embodiments, the methods disclosed herein can provide tungsten, vanadium, or both tungsten and vanadium in sufficient purities for commercial use.

The following invention relates to methods for reprocessing SCR catalysts. In a first embodiment, the invention relates to a method for reprocessing SCR catalysts, wherein an oxygen-containing compound of titanium and tungsten or molybdenum is removed from the catalyst and is then reacted with a vanadium compound. In a second embodiment, the invention relates to a method for removing titanium oxide and vanadium, molybdenum, and tungsten compounds from SCR catalysts and to a method for reusing these compounds in such catalysts.

The present invention relates to a method for leaching precious metals contained in a waste denitrification catalyst by using a pressure leaching process, and more specifically, to a method for leaching precious metals contained in a waste denitrification catalyst by using a pressure leaching process, the method comprising the steps of: forming a mixture by mixing a waste denitrification catalyst with a sodium salt solution; and leaching vanadium and tungsten contained in the mixture by feeding the mixture into a sealed pressurized reactor, and then heating and stirring the mixture.

The following invention relates to methods for reprocessing SCR catalysts. In a first embodiment, the invention relates to a method for reprocessing SCR catalysts, wherein an oxygen-containing compound of titanium and tungsten or molybdenum is removed from the catalyst and is then reacted with a vanadium compound. In a second embodiment, the invention relates to a method for removing titanium oxide and vanadium, molybdenum, and tungsten compounds from SCR catalysts and to a method for reusing these compounds in such catalysts.