Recovery of Elemental Boron From Boron carbide Using KCl-KF-KBF4 Electrolyte in Fused Salt Electroextraction Process

Abstract

Technology for extraction of elemental boron from boron carbide by fused salt electroextration using 70KCl-12KF-18KBF4 (in wt%) salt mixture as electrolyte was successfully demonstrated. The electrolytic cell was designed and fabricated suitably for using boron carbide as soluble anode, and boron was electroextracted on mild steel cathode plate. Initially, the salt mixture was characterized using differential thermal analysis (DTA) and thermogravimetry (TG) to understand the melting and evaporation behaviour of the salt. The electroextraction experiments were conducted at the optimized temperature of 860 °C applying a cathode current density (CCD) of 24.4 A dm−2 with varying times of 3, 7, 10, 12, and 24 h. High purity boron (∼98%) powder containing both rhombohedral and tetragonal crystals was successfully electroextracted. The morphology, composition and crystal structure of the electro-deposited boron was characterized using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction analysis. The kinetics of deposition of boron in cathode was found to be linear with an achievable current efficiency of 86.5%.