Magnesia from seawater: a review

Abstract

The process developed in the U K to produce magnesium hydroxide from seawater is described, together with the heat treatment that the hydroxide receives to produce the active oxide. Some of the characteristics required of the dolomite used in the process are also discussed. Impurities introduced by the seawater are noted and the means by which they can be reduced explained.

A systemic investigation on the hydroxylation behavior of caustic magnesia and magnesia sinter

“…On the other hand, for high solid load suspensions of polycrystalline particles at temperatures above 20 1C, dissolution occurs more rapidly. Consequently, the massive and exothermic precipitation of Mg(OH) 2 particles generate a thick and porous brucite layer [11,12,16,25,43]. Because of the large density mismatch (ρ MgO =3.5 g cm À 3 and ρ Mg OH ð Þ 2 =2.4 g cm À 3 ), this extra volume generated cannot be suitably roomed and induces compression stresses that crack the Mg (OH) 2 layer and the MgO beneath it.…”

“…Depending on the conditions employed (final temperature, residence time, atmosphere, and impurities), different types of polycrystalline materials can be obtained [1,[4][5][6][7][8][9]. The MgO grade known as caustic magnesia (CM) is produced through the rapid calcination of brucite or magnesite at temperatures of up to 800-900 1C in rotary and Herreshofftype kilns [8,9,11]. During calcination, such precursors undergo a series of topotactic changes before their total conversion into MgO ( Fig.…”

“…Schematic representation of topotactic changes that occur during calcination and sintering processes of MgO starting from Mg(OH) 2[4][5][6][7][11][12][13]. (SSA=specific surface area; ρ=solid density; CM=caustic magnesia; MS=magnesia sinter).…”

Preparation of periclase (MgO) nanoparticles from dolomite by pyrohydrolysis–calcination processes

“…Thereafter, we obtained the Mg‐rich solution containing 1.70 mol/L Mg 2+ and 3.89 mol/L Cl − ions for the pyrohydrolysis process. These values were higher than the concentration of the seawater that can be used to produce the MgO particles .…”

Effect of ZrO2on the densification behavior and properties of Indian magnesite

“…Magnesia refractory bricks also find their application in cement rotary kiln linings . Magnesia (MgO) is not available naturally in the oxide form, and the sources of MgO are natural magnesite, seawater, or inland brine . However, natural magnesites may contain impurities such as CaO, SiO 2 , Fe 2 O 3 , FeO, and Al 2 O 3 .…”