Characterization of Dolomitic Lime as the Base Reagent for Precipitation of Mg(OH)2 from Seawater

Abstract

The process of obtaining magnesium hydroxide from seawater involves precipitation of magnesium ions with suitable basic reagents, such as calcined dolomite. The purity of the magnesium hydroxide precipitate depends on dolomite characteristics; therefore, it is necessary to find high purity dolomite with good physical properties. The aim of this study was to characterize the specific dolomite from the location of Đipalo-Sinj (Croatia), its quality, and the favourable conditions for calcination. Certain physical and chemical characteristics were determined by pure chemical analysis, as well as by using TG/DTG-DTA, FTIR and SEM/EDS analysis. Good chemical quality of dolomitic lime (59.03 wt. % CaO, and 40.69 wt. % MgO) with low content of impurities was confirmed with the TG/DTG-DTA thermal analysis. In the atmosphere of air + CO 2 , dolomite decomposes to CaCO 3 and MgO in a temperature area between 415 and 824 °C; thereafter, another reaction begins-the decomposition reaction of calcium carbonate, completed at 897 °C. In air, the simultaneous decomposition of two carbonates occurs between 657-840 °C. The FTIR and EDS analyses confirmed the complete breakdown of carbonates at 950 °C. The main components (Mg, Ca, and O) confirmed the purity of the dolomite lime.

Techno-economic analysis of integrated processes for the treatment and valorisation of neutral coal mine effluents

“…The dolime is given by the calcination of dolomite that is a mixture of calcium and magnesium carbonates. The calcination process consists in heating the dolomite up to high temperatures, at which the dolomite decomposes into MgO and CaO and CO2 gas is released (Jakić 2016). Thus, the dolime suspension contains Mg 2+ and Ca 2+ ions in equal molar concentration, as in the dolime, and OHions, given by the reaction of the oxides with water.…”

The relationship between phase composition and conditions of sintering seawater derived magnesium oxide

“…2:3293 g L À1 MgO and 0:6229 g L À1 CaO Dolomite lime was obtained by the calcination of dolomite (location Ðipalo-Sinj, Croatia) at 950°C for 5 h. The composition of dolomite lime used as the precipitation agent was as follows [4] Seawater was pre-treated with sulphuric acid in order to remove bicarbonate (HCO 3 -) and carbonate (CO 3 2-) ions, followed by the removal of the liberated carbon dioxide (CO 2 ) by aeration in a desorption tower. The flow rate of the induced air was 120 L h -1 and the volumetric flow rate of seawater through the desorption tower was 6 L h -1 .…”

Mortars, plasters and pigments—research questions and sampling criteria

“…Fig. 2 Chemical reactions occurring during mortar production and weathering (from Davidson et al 1965;Böke et al 2006;Uğurlu and Böke 2009;Jakić et al 2016;Ponce-Antón et al 2018;Li et al 2020). The magnesian lime cycle is oversimplified because the formation of the different phases (e.g.…”