Analysis of particles size distributions in Mg(OH)2 precipitation from highly concentrated MgCl2 solutions

Abstract

Magnesium is a raw material of great importance, which attracted increasing interest in the last years. A promising route is to recover magnesium in the form of Magnesium Hydroxide via precipitation from highly concentrated Mg 2+ resources, e.g. industrial or natural brines and bitterns. Several production methods and characterization procedures have been presented in the literature reporting a broad variety of Mg(OH)2 particle sizes. In the present work, a detailed experimental investigation is aiming to shed light on the characteristics of produced Mg(OH)2 particles and their dependence upon the reacting conditions. To this purpose, two T-shaped mixers were employed to tune and control the degree of homogenization of reactants. Particles were analysed by laser static light scattering with and without an anti-agglomerant treatment based on ultrasounds and addition of a dispersant. Zeta potential measurements were also carried out to further assess Mg(OH)2 suspension stability.

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

“…The XRD pattern for the powder prepared by electrolysis (figure 4(c)) shows that with increasing electrolysis temperature, the diffraction peaks due to the (001), ( 101) and (110) crystal planes gradually increase, indicating that Mg(OH) 2 crystals preferentially grow on the (001), ( 101) and (110) crystal planes; that is, the increase in the number of primitive layers and primitive planes at the same time will inevitably increase the size of a single crystal. In addition, a high electrolysis temperature promotes the growth of crystals, which is why the crystal size increases with increasing electrolysis temperature [24,25]. When the electrolysis temperature is 70 °C, the diffraction peak of the (001) crystal plane is significantly enhanced, indicating that the primitive plane obtained under this condition grows better than the number of primitive layers, the shape tends to be thinner and flakelike, and the increased internal stress leads to the redispersal of the agglomerated powder.…”

Influence of Operational Strategies for the Recovery of Magnesium Hydroxide from Brines at a Pilot Scale

“…In such conditions, better mixing of the reactants led to a more homogeneous supersaturation level for the Mg­(OH) 2 reactive crystallization that produced weak agglomerates of nanosized aggregates that can be easily broken down. On the other hand, stronger agglomerates of nanosized aggregates were formed in test 1 that require high energy to be broken, as discussed by Battaglia et al…”

“…Five PSDs were measured after every 5 min of ultrasound treatment. As explained in ref, the use of a dispersant and sonication are required for the analysis of Mg­(OH) 2 suspensions due to its high flocculation tendency. In fact, only agglomerates made of the actual Mg­(OH) 2 particles would be measured, if they were not broken down.…”

High-Throughput Synthesis of Uniform Mg(OH)2 Nanoparticles in an Oscillating Feedback Minireactor Designed by the Selective Dimension Scale-Out Method

“…This is because the prepared small Mg(OH) 2 nanoparticles tend to agglomerate during the DLS tests, which could be confirmed by zeta potential measurements in the reported study. 9 In addition, as shown in Figure 12d,h, an average particle size of 66.0 nm with a narrow PSD (geometric standard deviation of particle size: σ g = 1.15) is achieved at Q total = 40 mL/min. Under this condition (Q total = 40 mL/min), it must be noted that the pressure drop within the microreactor would increase sharply (58.5 kPa), thus limiting the application for high-throughput production.…”

“…In addition, the shape, particle size, and particle size distribution (PSD) of Mg(OH) 2 play key roles in the sintering step for the synthesis of magnesium oxide. 5 Recently, a lot of methods have been developed to synthesize Mg(OH) 2 nanoparticles, including the wet precipitation method, 9 microemulsion method, 6 hydrothermal method, 10 and sol− gel method. 11 Among them, wet precipitation is the common one for industrial production owing to its rapidity and simplicity.…”