Method for preparation of high purity, crystalline cobalt nitrate from spent cobalt/silica catalyst

A method for preparing crystalline cobalt nitrate from spent catalyst of Co/SiO2, the method comprising:

• 1) calcining a spent catalyst of Co/SiO2 in the presence of air for between 3 and 6 hours at a temperature of between 350 and 500° C., cooling to room temperature, and grinding the spent catalyst of Co/SiO2 to yield a powder;
• 2) introducing the powder of 1) to a fluidized bed reactor, and heating the powder of 1) for between 8 and 12 hours in the presence of a mixed gas of H2 and N2 to obtain a heated powder, a volume ratio of H2 to N2 in the mixed gas being between 1:1 and 4:1;
• 3) adding the heated powder of 2) into excess dilute nitric acid solution, and then filtering to obtain a first cobalt nitrate solution;
• 4) adjusting a pH value of the first cobalt nitrate solution of 3) to 1.5 using an alkali solution, adding a preheated oxalic acid solution having a temperature of between 25 and 80° C. and a pH value of 1.5 to the first cobalt nitrate solution in a water bath of between 25 and 80° C. to obtain a resulting solution, adjusting a pH value of the resulting solution to 1.5 using a dilute alkali solution, immediately filtering the resulting solution to yield a precipitate of cobalt oxalate, and then washing the precipitate of cobalt oxalate using deionized water to yield a neutral filtrate, wherein a mole number of oxalic acid in the oxalic acid solution is controlled to be between 2 and 3 times a mole number of cobalt in the cobalt nitrate solution;
• 5) drying the precipitate of cobalt oxalate of 4) to obtain a dried precipitate, and then calcining the dried precipitate for between 4 and 8 hours at a temperature of between 550 and 650° C. to yield cobalt oxide;
• 6) dissolving the cobalt oxide of 5) with a dilute nitric acid solution to yield a second cobalt nitrate solution;
• and
• 7) evaporating and crystallizing the second cobalt nitrate solution to yield crystalline Co(NO3)2.6H2O.