Effect of temperature on the stability constants of zinc- nitrilotriacetic acid- ammonia system

To study the effect of temperature on the stability constant of zinc-nitrilotriacetic acid- ammonia (Zn-NTA-NH3) system, the protonation constants of the free ligands and stability constants of the ternary complexes were determined via pH potentiometric method at temperatures of 25.0 °C, 40.0 °C, 55.0 °C, 70.0 °C. The first and second stability constants of Zn-NTA-NH3 system decrease from 11.83, 14.00 to 10.72, 12.81, respectively, with the temperature increasing from 25.0 °C to 70.0 °C. While those of the Zn-NTA-H2O system decrease from 9.20, 11.98 to 8.27, 11.29. These results indicate that Zn-NTA-NH3 system is more stable than Zn-NTA-H2O system, leading to enhanced zinc leaching efficiency in the zinc leaching process.