METHOD FOR RECOVERING CERIUM

摘要

PROBLEM TO BE SOLVED: To provide a method for efficiently recovering cerium with high purity from a solution containing cerium and chromium and to provide a chromium etching solution using the recovered cerium. SOLUTION: A reducing agent is added to a solution containing cerium and chromium to reduce tetravalent cerium and hexavalent chromium in the solution respectively into tervalent cerium and tervalent chromium. An alkali agent is added to the reduced solution to control its pH to the range of 1 to 6, and tervalent chromium is adsorbed and removed by using ion exchange resin. Next, an alkali agent is added to the reduced solution freed from tervalent chromium to control its pH to >=8, and tervalent cerium is precipitated and recovered as cerous hydroxide. As the reducing agent, one or more kinds of compounds selected from organic acid, alcohol and aldehyde are used, and, as the ion exchange resin, the one having a tertiary amino group on an ion exchange group is used. The recovered cerium is made into a cerium source of ammonium cerium (IV) nitrate and is reutilized for a chromium etching solution.