Study On Oxidation Of Cerium In Alkaline Cake Of Baotou Rare Earth Concentrate

A new technology was present based on traditional technology of decomposing Baotou rare earth concentrate with alkaline method. In order to divert cerium into prior dissolving dregs to be redissolved and separated while prior dissolving using chloride acid, some oxidant was used to oxidize trivalent cerium in alkaline cake to tetravalent cerium after decomposing rare earth using alkali liquid. In this flow sheet, on the one hand, the excess sodium hydroxide after decomposing can fulfill the alkalinity oxidation reaction need; on the other hand, pressure of extraction section can be greatly alleviated while very large proportion of cerium has been separated from prior solutionCerous oxidation is the best key step in new technology. Air, oxygen and sodium hypochlorite was used respectively to oxidize cerium in alkaline cake of Baotou rare earth concentrate in this study.Orthogonal design was used to investigate effects of reaction temperature, reaction time, solid—liquid ratio, basicity and air inlet speed on oxygenation ratio in the method of selective oxidation of air and oxygen, and the best conditions of two methods by means of analysis of range and variance were found out. Cerous oxygenation ratio could be up to 73.50% at reaction temperature 80℃, reaction time 16h, basicity 0.3mol/L, solid—liquid ratio selected at will between 1:11 and 1:8, air inlet speed selected at will between 0.6L/min and 1.5L/min in the method of selective oxidation of air; cerous oxygenation ratio could be up to 75.81% at reaction temperature 80℃, reaction time 16h, basicity 0.2mol/L, solid—liquid ratio 1:11 and air inlet speed selected 0.04L/min in the method of selective oxidation of oxygen. Using orthogonal design to optimize conditions of new technology is successful.Cerium chloride solution was used as feed stock oxidized at basic condition in the method of selective oxidation of sodium hypochlorite. The results indicate that cerous oxygenation ratio can overtop 93% at room temperature, pH=8～9 and measure ratio 0.7 for 1.5h. When sodium hypochlorite was used to oxidize cerium in alkaline cake, the results indicate that, at pH=8～9, due to the blocking of slag to contact of sodium hypochlorite and cerium hydroxide and catalytic decomposition of Fe3+,Mn2+to sodium hypochlorite, cerous oxygenation ratio could reach up to 85% while measure ratio was augmented to 9 and reaction time was prolonged to 2.5h.