Magnesium Hydroxide Nanoparticles Production from Natural Bitterns

Magnesium hydroxide nanoparticles are widely employed in numerous industrial applications. Several preparation methods have been proposed using mainly synthetic Mg²⁺ containing solutions. In the present work, the possibility of producing Mg(OH)₂ nanoparticles from real bitterns, the by-product of sea salt production, is investigated. Bitterns are highly concentrated Mg²⁺ containing solutions whose exploitation can turn a waste into valuable products embracing the circular economy idea. Two bitterns collected from Galia and Margi saltworks of the district of Trapani (Italy) were studied. Galia and Margi bitterns had a 1 M and 2.5 M Mg²⁺ concentration, respectively. A 2 mm diameter circular-cross sectional T-mixer was adopted to ensure fast reactant mixing. NaOH solutions were employed as precipitant agents. Mg(OH)₂ nanoparticles characterized by cationic and mass purity higher than 99 % and 90 %, respectively, were successfully produced when treating Galia bitterns, while the excessive Margi Mg²⁺ concentration yielded stronger micrometer Mg(OH)₂ agglomerates.