A Novel Pilot-scale Crystallizer for the Production of Mg(OH)2 Powders from Saltworks Bitterns

Magnesium hydroxide suspensions and powders are widely used products in several industrial fields. Among the various synthetic methods, the reactive crystallization technique from saline solutions has low environmental impact, although difficulties are often encountered to obtain products with high technical specifications. In this study, Mg(OH)2 suspensions and powders were synthesized using an innovative crystallizer called 2nd generation "Magnesium Crystals Granulometry Controlled Reactor". Two bitterns with a Mg2+ concentration of 2 M were used, a real one collected from the Trapani saltworks (Italy) and an artificial one. 0.5 M NaOH solutions were employed as the alkaline stream. The obtained solids were characterized by mass purities greater than 98%, with magnesium ions recoveries exceeding 99%. The produced suspensions exhibited excellent settling and filtration properties: in the best scenario, the initial settling velocity and the filtration rate were 433 mm/h and 58.8 kg/m2·h, respectively. Results mark the considerable potential of the innovative pilot-scale crystallizer in producing Mg(OH)2 suspensions with excellent solid/liquid separation properties, as well as highly pure solids in line with market standards.