Investigation on the reaction progress of titanium and lead chloride in NaCl-KCl melt

Abstract

The in-situ preparation of NaCl-KCl-TiClx molten salt electrolyte was investigated by replacement of PbCl2 and Ti in a NaCl-KCl melt at 750 ℃. The reaction progress of PbCl2(3.38 wt.%) with excess Ti was monitored in real-time by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. The thermodynamic calculation and electrochemical test results show that titanium ions are mainly generated in the form of Ti(III). The redox peak current of Pb(II) decreases rapidly and drops to below the detection limit of the electrochemical tests after 275 min. Simultaneously, the reduction peak current of Ti(III) increases rapidly from 0 to 75min, and reaches to the maximum value until 275 min. At this time, the replacement reaction has been completed, and the NaCl-KCl-TiClx(2≤x≤4) molten salt is obtained finally. Ti-Pb alloy was obtained by depositing at -1.0 V(vs. Ag/AgCl) for 30 min during the replacement process. Lead by-product of the replacement reaction was precipitated and collected. Electrolytic refining was carried out successfully using the NaCl-KCl-TiClx molten salt electrolyte prepared as described above. The results demonstrated that a stable NaCl-KCl-TiClx molten salt electrolyte can be obtained by the present method. The study provides a new thinking for the preparation of molten salt electrolyte containing titanium ions, and also provides theoretical references for the electrolytic refining of titanium and the preparation of titanium alloys by electrodeposition.