Effect of various mineral acids during the hydrothermal leaching process of NiTi Alloy

Nickel and titanium-based alloys are commonly used for engineering or medical applications. NiTi alloys are recycled as additive materials at the end of their lifetime. Separate recovery of metals present in NiTi alloy is possible via hydrometallurgical methods; however, NiTi alloys are highly resistant to corrosion. Various mineral acids (H2SO4, HCl, HNO3, H3PO4) have been investigated, and the effect of H2O2 in the leaching medium has also been explored. Different leaching yields have been observed, and correlations between them according to acid treatment conditions have been established. SEM, XRF, and EDS techniques characterized alloys' microstructure and chemical properties. Among mineral acids, H2SO4 and HCl illustrated the highest extraction efficiencies. However, the addition of hydrogen peroxide decreased this efficiency severely. The kinetics of dissolution was obtained through decreased leaching efficiency with the addition of hydrogen peroxide.