Recovery of tungsten trioxide from waste diamond core drilling crowns by nitric acid leaching

Abstract

A cost-effective and simple hydrometallurgy procedure for recycling the diamond core drilling crowns by nitric acid leaching, followed by the sodium hydroxide leaching, has been developed. The effect of temperature, nitric acid/sodium hydroxide concentration, leaching time and stirring rate were studied. For the acid leaching process the optimal values for parameters were 60 °C, 1.0 M HNO3, 2.5 h, and 800 rpm. It has been noted that the key factors in the alkaline leaching process were temperature and NaOH concentration. For the alkaline leaching, the optimal parameters were 100 °C, 40% concentration of NaOH solution, and leaching time of 4 h. Identification and characterisation of products in all technological processes were performed by X-Ray Diffraction (XRD), scanning electron microscope using energy-dispersive X-ray spectroscopy (SEM-EDS), and laser desorption ionisation mass spectrometry (LDI-MS). The analysis of solutions in all phases was performed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The use of LDI-MS as a new approach to identify the products after phases in the recycling process was an important part of the study, and the results were consistent with the XRD analysis. The total tungsten recovery was over 95.6%, with a high purity of the obtained tungsten trioxide.