A study of separation of iron powder and preparation of Ti-Al alloy by selective electrolysis of ilmenite

Abstract

Titanium and its alloys are very attractive materials due to its higher weight to strength ratio and high resistance towards corrosion. In this investigation, a laboratory scale trial has been conducted for extraction of titanium from ilmenite by fused salt electrolysis. Ilmenite prepared from beach sand in the purity of 95–96% was used as raw material for molten salt electrolysis studies. Process parameters for molten salt electrolysis were optimized by: (1) investigations on the degree of dissolution of iron and titanium from ilmenite in electrolytic baths, (2) optimization of bath composition and temperature to maximize the difference in the solubility of iron and titanium and (3) optimization of the degree of mechano-chemical activation of ilmenite for maximizing the difference in solubility. The molten salt electrolysis experiments were conducted for: (i) selective removal of iron and production of “synthetic rutile”, and (ii) electrolysis of “synthetic rutile” to produce titanium and its alloys. A suitable electrolytic cell was fabricated and the electrolysis was conducted in two stages using optimized mixture of chloride and halide bath at 900C in an inert atmosphere. In the first stage, the electrolysis was conducted of low voltage for selective electrolysis of iron ions to deposit on cathode. The TiO2 rich residue left in the anode chamber was collected and named as “synthetic rutile”. The efficiency of the 1st stage process was 40–45% and the purity of iron and titanium dioxide were 96–97% and 92%, respectively. In the second stage, the electrolysis was conducted at higher potential for preparation of Ti/ Ti-Al alloys using synthetic rutile prepared in the first stage process. The cathodic deposits were characterized by chemical method, namely by conventional technique as well as AAS, optical microscopy, XRD, SEM- EDAX. From the preliminary investigations, it can be inferred that Fe separation is feasible and Ti has been successfully deposited in the cathode as Ti-Al intermetallic.