Characterization of Mg(OH)2 powders produced from real saltworks bitterns at a pilot scale (Pre-print version)

The growing demand for a reliable supply of minerals has pushed the European Union toward seeking novel mineral sources. In the present work, the recovery of magnesium, in the form of magnesium hydroxide, Mg(OH)₂, from saltworks bitterns was investigated at a pilot scale. The natural bittern collected from Margi saltworks (Trapani, Italy) was treated with synthetic sodium hydroxide (NaOH) solutions. The influence of different reactant concentrations, flow rates and pH environments, on Mg(OH)₂ particle sizes, filtration characteristics, Mg²⁺ extraction performance and the Mg(OH)₂ solid purity was thoroughly assessed. The presence of additional dissolved salts in NaOH solutions was also analyzed. The pH environment was found to be the most crucial parameter. On the one hand, high pH values ensured high Mg²⁺ recovery and powder purities, i.e. > 98%, with boron content complying with market requirements. On the other hand, filtration characteristics considerably worsened due to the lyosorption phenomenon.