Lline precipitates in Mg-dominated solutions. This is surprising mainly because 33 to 17 of solvated cations in these scenarios (Mg/Ba and Mg/Ca = two and five, this study and Xu et al., 2013 [51]) are barium and calcium and really should lead to witherite and calcite crystallization, as they didMinerals 2021, 11,10 ofin aqueous environments. A plausible interpretation is the fact that Mg2 , which may be much less stable in an un-hydrated type as a result of higher charge density relative to Ba and Ca ions, has the benefit to bind with CO3 2- first. When Mg would be the minority ion in the option and binds preferentially with carbonate ions, Ba2 and Ca2 can interact together with the remaining CO3 2- to type witherite and calcite or can be incorporated inside the prior-formed Mg-CO3 unit to crystallize in norsethite and high-Mg calcite. In Mg-dominating options, having said that, rapid interactions of Mg with CO3 ions cause amorphous magnesium carbonate precipitation (around the assumption that the Mg O3 units can’t stack to form 3D crystalline structures as a result of entropy penalty in the CO3 Ziritaxestat Protocol groups) [51] as well as a swift consumption of CO3 2 , leaving Ba2 and Ca2 behind to keep within the remedy without their host minerals witherite and calcite or to take place as minor elements within the amorphous phases. It is actually worth noting that many prior research really discovered [4,38,40,45,56] BaCO3 , rather than MgCO3 becoming a precursor of norsethite at atmospheric circumstances. Thinking of the recent discovering that norsethite formation proceeds via a crystallization (chiefly of Na3 Mg(CO3 )two Cl, with minor witherite and norsethite) issolution ecrystallization (of norethite) pathway [38], we suspect the incorporation of Ba in to the trigonal carbonate structure (or the transformation of BaCO3 from orthorhombic to rhombohedral class) is a kinetically unfavored method. This can be particularly accurate at low T, where the formation of ordered MgCO3 is challenging plus the orthorhombic template for BaCO3 to epitaxially grow on is lacking. As such, witherite is expected to form first but dissolves subsequently to release Ba2 after MgCO3 units are in spot to crystallize MgBa(CO3 )two . At greater T when magnesite can readily type along with the orthorhombic to rhombohedral transformation for BaCO3 is significantly less hindered, one should count on MgCO3 to be a precursor of norsethite. This view is in truth constant with the experimental observation that magnesite is definitely the only precursor through norsethite crystallization at temperatures above 100 C [57]. four.three. Relative Effect of Mg Hydration and Structural Restraints The above discussion seems to converge on a conclusion that each Mg hydration and lattice structure are in play in limiting dolomite formation at ambient conditions. We now endeavor to evaluate the relative significance of the two barriers. At a microscopic level, crystallization is characterized by the method of particle attachment and detachment. A single effective strategy to quantify this process is by way of the application of your transition state theory. Given that dolomite (and magnesite inside the same sense) is definitely the thermodynamically stable phase at ambient conditions [18,581], the difficulty to crystallize such minerals is safely ascribed for the DMPO Protocol reaction kinetics. In the TST method, the kinetic limitations could be assessed particularly by examining the concentration on the activated complicated at constant temperature. To a first-degree approximation, we assume the nucleation of norsethite proceeds by means of the following reaction (Equation (1)): Mg2.