Method of removing iron ions from a solution containing neodymium, praseodymium, dysprosium and iron

Abstract

The present invention discloses a method of removing iron ions from a solution containing neodymium, praseodymium, dysprosium and iron, in which glucose is added into an acid solution containing neodymium, praseodymium, dysprosium and iron, at a molar ratio of iron/glucose at 0.2-2, and mixed evenly, and the solution is then hydrothermal treated, and after that an iron-containing precipitate is formed at the bottom, and the residual concentration of iron in the supernatant is less than 20 mg/L, and the retention rate of the rare earth elements is more than 97%. The present invention may separate iron from a solution containing neodymium, praseodymium, dysprosium and iron efficiently, which solves the pollution problem of iron to the extraction agent during the purification of the rare earth solution, and enhances the purity and utility value of the rare earth elements in the solution; the present invention is applicable to treat a rare earth solution containing a high concentration of iron or an acid solution of wastes, in which the retention rate of the rare earth elements is high, and the residual concentration of iron in the solution is low, with a simple operation and a low cost.

1 . Method of removing iron ions from a solution containing neodymium, praseodymium, dysprosium and iron, which is characterized in that, including the following steps:
 A. taking a solution containing neodymium, praseodymium, dysprosium and iron, with a pH value between 0.1-3.5;   B. adding glucose to the solution from step A, and mixed evenly;   C. heating the mixed solution obtained from step B to 60° C.-350° C., keeping the temperature constant for 5 minutes-72 hours;   D. after the solution from step C is cooled, a precipitate is formed at the bottom, and the concentration of iron in the supernatant is less than 20 mg/L, the retention rate of the rare earth elements is more than 97%.   
     
     
         2 . The method according to  claim 1 , which is characterized in that, the solution from step A comprised, but not limited to, the solution generated after extracting the rare earth materials by an acid, wherein the acid refers to hydrochloric acid or nitric acid. 
     
     
         3 . The method according to  claim 1 , which is characterized in that, the content of iron in the solution from step A is between 0.15 g/L-300 g/L. 
     
     
         4 . The method according to  claim 1 , which is characterized in that, the content of iron in the solution from step A is between 4.2 g/L-300 g/L, in which ethylene glycol or ascorbic acid is employed instead of glucose. 
     
     
         5 . The method according to  claim 4 , which is characterized in that, the additive amount of ethylene glycol is based on the molar ratio of iron/ethylene glycol at 0.5-3.8, after treatment with ethylene glycol, the residual concentration of iron in the supernatant is less than 500 mg/L. 
     
     
         6 . The method according to  claim 4 , which is characterized in that, the additive amount of ascorbic acid is based on the molar ratio of iron/ascorbic acid at 0.1-1.5, after treatment with ascorbic acid, the residual concentration of iron in the supernatant is less than 800 mg/L. 
     
     
         7 . The method according to  claim 5 , which is characterized in that, after collected, the supernatant is aerated with air for 10 minutes-2 hours, and then adjusted to pH 4 with ammonia water, making iron to precipitate, while the rare earths also co-precipitating to generate a precipitate, the content of iron in the supernatant is less than 15 mg/L, and the retention rate of rare earth elements is between 30%-52%. 
     
     
         8 . The method according to  claim 7 , which is characterized in that, after the above precipitate is dissolved with hydrochloric acid or nitric acid according to the solid-to-liquid ratio of 40%-70%, the concentration of iron in the solution is more than 1500 mg/L, then it is treated according to step B, step C and step D, successively. 
     
     
         9 . The method according to  claim 1 , which is characterized in that, the above step B particularly further included: the additive amount of glucose is based on the molar ratio of iron/glucose at 0.2-2, the glucose is mixed with wastes containing neodymium, praseodymium, dysprosium and iron, into which then an acid is added, and finally the glucose is heat treated according to step C. 
     
     
         10 . The method according to  claim 1 , which is characterized in that, the heating in the above step C employs a programmed heating, the heating conditions are confined as follows: when the temperature is between 60° C.-120° C., the duration of heating is not less than 10 hours; when the temperature is between 300° C.-350° C., the duration of heating may less than 30 minutes.