Novel Titanium Electrowinning Process Using Specialized Segmented Diaphragms

Titanium metal, with high strength-to-weight ratio, is an important structural metal for aerospace and defense applications. However, titanium is expensive largely due to the energy-intensive nature of the Kroll process conventionally used for titanium extraction from ore. At Case Western Reserve University, we are developing an alternative low-cost titanium extraction process based on electrolysis of titanium salts from halide melts. The key innovation in our titanium electrowinning process is a specialized diaphragm stack, which separates the catholyte and anolyte compartments of the cell. The diaphragm stack eliminates extraneous reactions in the electrowinning cell, enabling stable and energy-efficient electrolytic extraction of high-purity titanium sponge. In this talk, we will outline the fundamental electrochemical principles governing the operation of this novel electrowinning process. We will also present proof-of-concept results collected on a prototype electrowinning reactor, which show feasibility of this revolutionary electrolytic titanium extraction approach. Broader impacts of our electrowinning approach to other multivalent metal systems will be discussed.

Figure 1. Schematic of our titanium electrowinning cell, showing a stack of thin diaphragm separators, each with thickness L. Diaphragm thickness is selected so that the potential drop across the diaphragm is lower than the thermodynamic onset potential for bipolar reactions. This design eliminates extraneous bipolar reactions in the cell, enabling stable cell voltage [as shown in (a)] and efficient titanium electrowinning [as shown in (b)].