Parameters affecting Mg(OH)₂ extraction from serpentinites in lithuania for the purpose of CO₂ reduction by mineral carbonation

Abstract

Mineral sequestration has a great potential for abating CO 2 emissions, especially at locations where no opportunities for CO 2 geological storage exist. This article focuses on the mineral carbonation of magnesium silicates, that is, serpentinites, which offers an attractive option for CO 2 emission mitigation in Lithuania. Mineral CO 2 carbonation in a staged gas/solid process route is one of the most prospective approaches. The process was conducted in several steps. Firstly, extraction of the magnesium hydroxide from serpentinite via a solid/solid reaction between serpentinite and ammonium sulfate salt at a temperature interval of 500-540 C was carried out. The maximum Mg extraction (53.70 %) was obtained with the mass ratio of reactants of 2 g serpentinite/3 g ammonium sulfate, reaction temperature, and time of 520 C and 20 min, respectively. Secondly, the process of precipitation of Mg(OH) 2 took place. The effect of precipitation of the Fe-containing compounds (first step) and the Mg(OH) 2 (second step) was analyzed. At the pH of 8-10 and 10-12, compounds of Fe and Mg precipitated, respectively. The optimal Fe removal and Mg extraction was achieved at the pH of the $9.5 for the first step and at the pH of $11.50 for the second step. Finally, the carbonation of extracted magnesium hydroxide was accomplished and reached the effectiveness of 65 % after 15 min at 535 C, 51 bar.

Serpentinite Carbonation Process Routes using Ammonium Sulfate and Integration in Industry

“…An Mg(OH) 2 produced from a Lithuanian serpentinite was carbonated up to 65 % in 15 min in 51 bar pure CO 2 at 535 °C whereas 70 % conversion in 30 min was obtained with Mg(OH) 2 produced from Portuguese rock at 510 °C, 20 bar pure CO 2 , size fraction <74 μm . More detail on Mg(OH) 2 production and carbonation is given in the Experimental Section.…”

“…Typical reaction temperatures for the serpentinite/AS salt reaction are somewhat lower than the carbonation temperature, at 400–440 °C so as to avoid decomposition and sublimation “losses” of the AS salt as recently reported . On the other hand, with increased fractions of iron oxides and silicates in the serpentinite a temperature of up to 520 °C (for 20 min) gave the highest extraction yields for Mg and Fe …”

Carbonation of BOF Slag in a Rotary Kiln Reactor in View of the Scale‐Up of the Wet Route Process

“…In general, carbon mineralization can be achieved by two different routes: 1) an indirect process in which the dissolution of the reactive phases and the precipitation of the respective carbonates are performed separately in order to optimize each step; examples of this route are reported for Mg(OH) 2 or for CaO produced by limestone calcination ; 2) direct carbonation, where Ca/Mg oxide or silicate rich residues are carbonated in a single process step in which both dissolution and precipitation take place. Direct carbonation is generally applied via an aqueous phase process performed either through the slurry‐phase route, characterized by a liquid to solid ratio (L/S) above 1 w/w, or by the wet (or thin film) one, with a L/S ratio below 1 w/w .…”

Mineral carbonation of a desulfurization residue for CO2 sequestration

“…In 2013, global CO 2 emissions hit a new record, reaching about 36.1 billion tons. [9][10][11][12][13][14][15][16][17] The carbonation of natural minerals oen requires harsh reaction conditions because the natural minerals are thermodynamically stable. 7 The global carbon cycle is sufficiently extensive to conclude that natural processes cannot absorb all the anthropogenically produced carbon dioxide (CO 2 ) in the coming centuries, so adaptation technologies are urgently required.…”