A Different Solvent for Dissolution of Ulexite: A Kinetic Study in Ammonium Hydrogen Sulphate

Abstract

This research delves into the dissolution kinetics of ulexite, a mineral characterized by its high boron content, in ammonium hydrogen sulphate (NH₄HSO₄) solution. Considering Turkey's pivotal position in the global boron market, the study is geared towards discovering a greener and more cost-effective alternative to the conventional sulfuric acid process for producing boric acid. Dissolution experiments were systematically performed under varying conditions, including temperatures of 30°C to 80°C, NH₄HSO₄ concentrations ranging from 0.2 M to 1 M, solid-to-liquid ratios of 0.02 to 0.1 g/mL, stirring speeds between 200 and 600 rpm, and particle sizes from 53 to 600 micrometers. The findings revealed that the dissolution rate increased with rising temperatures, higher NH₄HSO₄ concentrations, and smaller particle sizes. Specifically, at 80°C and NH₄HSO₄ concentration of 1 M, the dissolution rate was considerably higher than under lower temperature and concentration conditions. In contrast, a higher solid-to-liquid ratio resulted in a reduced dissolution rate, indicating that an optimal balance must be struck for efficient processing. Kinetic analysis, employing the shrinking core model, revealed an activation energy of 42.98 kJ/mol, signifying that the process is governed by chemical reactions. These insights suggest that NH₄HSO₄ could serve as a promising alternative solvent for boric acid production, offering potential environmental and economic advantages. Nonetheless, further research is essential to assess its feasibility for commercial use. Kinetic dissolution with ammonium hydrogen sulphate provides more efficient and faster results compared to dissolution with conventional solutions. © 2025, Iranian Institute of Research and Development in Chemical Industries. All rights reserved.