Boric Acid Production from a Low-Grade Boron Ore with Kinetic Considerations

Abstract

The most important Iranian boron reserves are in the basin of Ghezel Ozan, a river in the West and Northwest area of Zanjan. In the present study, boric acid production from an Iranian low-grade borate ore by hydrometallurgical process was investigated. In order to produce boric acid, boron ore was reacted with sulphuric acid. The influence of four parameters on the course of reaction such as pH, temperature, liquid to solid ratio, and reaction time was examined. Optimum condition for leaching part was obtained in temperature of 90°C, reaction time of 2 hours, L/S ratio of 3, and pH of 1. Under these conditions, the recovery of boron acidic leaching was reported to be 92.21%. Neutralization of pulp was done by lime. Finally, boric acid was obtained by crystallization. The purity of produced boric acid was 99.56%. The data obtained from the acidic leaching kinetics indicated that the dissolution of boron ore is fluid film diffusion controlled reaction and the reaction activation energy equals to 11.6 kJ/mol. Enthalpy of activation and entropy of activation were 11.2 kJ/mol and -246.3 J/(mol.K) respectively.