Electro-oxidizing Cerium (Ⅲ) To Cerium (Ⅳ) On Cnode And Simultaneous Reducing Cu(Ⅱ) On Cathode To Produce Copper Powder

Industrialization of electro-oxidizing Cerium(III) to Cerium(IV) has been a important project for long time because of its low cost, no chemical oxidation agents used and no pollution to rare earths productions. Many factories focus on this method to reduce the process cost to deal with the price drop of cerium products special for recent years. The oxidation of Cerium(III) to Cerium(IV) had been unsuccessfully used in sulfuric acid solution in spite of nitric acid media for low solubility of rare earths sulfate, low current efficient, high consume of electric energy and expensive electrode material of platinum. The separation of rare earth in sulfuric acid media had been a major process with development of Chinese rare earth industry. It is requirements of present process and current situation of Chinese rare earth factories, also result of increasingly ripe for rare earth market to invent a way of electro-oxidizing Cerium(III) to Cerium(IV) in sulfuric acid media at lower cost.Structural design suitable to electro-oxidizing Cerium(IH) to Cerium(IV) in sulfuric acid had been achieved by selection of electrolysis parameters. Systematic studies of electro-oxidizing Cerium(III) to Cerium(IV) had been carried out by employed firstly lead alloy and copper as anode and cathode respectively, and with ion-exchange membranes as cell diaphragms. The results that platinum anode and ion-exchange membrane made in overseas can be replaced by lead alloy and domestic membranes broke the limit of high investment caused by platinum anode and membrane. Current density, anolyte acid and concentration of SO42" in anolyte are notable factors influencing the current efficiency, oxidation rate and cell potential. The electro-oxidation in anion exchange membrane system can be carried out in larger range of anolyte acid but cation exchange membrane system only for over 0.75mol/L. At dilute Cerium(III) solution, the anion exchange membrane system has higher current efficiency than cation exchange membrane system.Aimed at the decrease of current efficiency with the procedure of electrolysis, the method of variable current density electrolysis was put forward firstly. The oxidation rate and anode current efficiency can be kept over 98% and 80% which are higher about 8% and 15% than the values reported in the papers by variation of current density according to concentration of Cerium(III) in this electrolysis process. By the varying current density, the cell potential decreases from 3.0V for constant current electrolysis to 2.2-2.5V, consume of electric energy for CeO2 decrease from 1.6KWh/t to 0.61KWh/t. The relation between current density and electrolysis time had been induced and its correctness had been verified with the test dates.Cathode-current is wasted for deposition of H2 in the process of electro-oxidizing Cerium(III) to Cerium (IV) in the available ways. For purpose of the using electric energy, the method of electro-oxidizing Cerium(III) to Cerium(IV) on anode and simultaneous reducing Cu(II) on cathode to produce copper powder was represented firstly. So the deposition of copper powder in the membrane electrolysis system was processed firstly. The consumption of electric energy of copper powder approached to the ones without cell diaphragms because of high current efficiency and powder yield rate. Electro-oxidizing Cerium(III) to Cerium(IV) on anode and simultaneous reducing Cu( II)on cathode to produce copper powder does not make the electrolysis complicated, but reduces the cell voltage about 0.2-0.5V further. The cell voltage and energy consumption of cerium dioxide decrease to 2.0V and 0.5KWh/kg respectively.Copper powder is made without investment and consume of energy in this method. According to profit of copper powder made by available process and the decrease of energy cost, the extra profit for It CeO2 brought by copper powder is about 1000yuan RMB without counting investment interest, depreciation of equipments, service cost and worker's salary.The surface complex-discharging kinetics and mechanism of the...