Influence of Electrodes Surface Area Ratio on Titanium Electrorefining Process

Abstract

Listen

Translate article

Most titanium is commercially produced by the Kroll process, which was developed in the 1960s. Recently, it has been criticized for its high energy consumption, toxicity, significant greenhouse gas emissions, and the generation of iron-contaminated titanium scrap. Consequently, numerous attempts to develop alternative methods for titanium production have been widely studied in the past few years, electrorefining is one of these methods.The titanium electrorefining process is based on the transfer of titanium from an impure electrode (CuTi anode) to another electrode (cathode) in an electrolyte environment. The configuration of the electrodes is highly important for the electrorefining process, as it can limit conditions for efficient electrorefining and reduce the quality of the produced titanium deposits.Titanium electrorefining tests were conducted in molten LiCl-KCl-NaCl with 7.5 mol.% of TiCl2, in an argon atmosphere at 600 °C. A CuTi ingot was used as the anode, and a steel electrode served as the cathode. The influence of the electrodes' surface area was studied to improve the efficiency of the electrorefining process and the quality of titanium deposits. The surface area ratio of the anode to cathode was varied from 2.28 to 7.84, and the current density applied to the cathode ranged from 12.5 to 104 mA/cm².Electrode potentials, cell voltage, and maximum current density were measured using a data logger and DC power supply for experimental setups with various surface area ratios of the electrodes. The experimental results indicated that current efficiencies ranged from 69 to 82.5% based on weighing the leached titanium deposits. Typically, lower current densities resulted in higher current efficiencies and improved quality of titanium deposits. Higher cell voltages and potentials were observed in setups with lower surface area ratio.Morphology and chemical analysis of titanium deposits were obtained through SEM/EDS analysis and N/O analysis. It was found that higher current densities resulted in finer titanium deposits and increased oxygen content in the deposits. The optimal surface area ratio was estimated to be 2.84 at a current density of 62.5 mA/cm² for producing large dendritic titanium with oxygen as low as 963 ppm, and as 5.21 at current density of 104 mA/cm2 for production of fine titanium powders with oxygen of 3163 ppm.