Effect of processing parameters on the properties of electrolytically prepared Mg(OH)2 powders

Abstract

In this paper, Mg(OH)2 was prepared by the diaphragm electrolysis method using bischofite (MgCl2·6H2O). The influence of electrolysis process conditions such as current density, electrolysis temperature and electrolyte concentration on powder particle size is discussed. The electrolytic product Mg(OH)2 powder was characterized by laser particle size analysis, XRD, SEM, BET, XRF, and DSC-TGA. The results show that the particle size of Mg(OH)2 powder first increases and then decreases with increasing current density and reaches a maximum D50 value of 20.1 μm at a current density of 0.04 A cm−2. The Mg(OH)2 powder particle size first decreases, then increases and then decreases with increasing electrolysis temperature, at an electrolysis temperature of 60 °C and 70 °C, the particle size reaches a maximum D50 value of 23.8 μm and a minimum D50 value of 7.7 μm, respectively. The Mg(OH)2 powder particle size first increases and then decreases with increasing electrolyte concentration and reaches a maximum D50 value of 22.3 μm at an electrolyte concentration of 0.7 mol l−1. The Mg(OH)2 powder prepared at a current density of 0.3 A cm−2, electrolyte concentration of 0.3 mol l−1 and an electrolysis temperature of 30 °C shows an average particle size of 13.8 μm, a purity higher than 98.66%, and a sheet-like structure. The surface area is 58 m2 g−1. The Mg(OH)2 powder can be decomposed at 300 °C–400 °C and calcined at 400 °C for 2 h, through SEM and Scherrer formula calculation, the calcined product is nano-MgO powder with good crystallinity.