Of2Minerals 2021, 11,Minerals 2021, 11, x FOR PEER Overview 7 of7 ofFigure 2. XRD spectra precipitates within the FMD experiments (ns: norsethite, wt: witherite). All Figure two. XRD spectra of theof the precipitates inside the FMD experiments (ns: norsethite, wt: witherite). visible peaks below two of 55 of 55 had been in a position to be assigned to norsethite and witherite, suggesting All visible peaks under had been in a position to be assigned to norsethite and witherite, suggesting that these two minerals may well be the only phases that occurred inside the experiments. Notice the lack of that these two minerals might be the only phases that occurred within the experiments. Notice the lack of crystallinity at circumstances of 2Mg:1Ba and 5Mg:1Ba also as the presence of norsethite (ten.1) and crystallinity at conditions of 2Mg:1Ba and 5Mg:1Ba as well because the presence of8 norsethite (10.1) and Minerals 2021, 11, x FOR PEER Review peaks at 1Mg:5Ba. of 16 (00.3) (00.3) peaks at 1Mg:5Ba.Figure3. SEM photomicrographs in the from the precipitates in FMD experiments (upper: Mg/Ba = five:1, amorFigure 3. SEM photomicrographs precipitates in FMD experiments (upper: Mg/Ba = five:1, Olesoxime supplier amorphous aggregates; middle: Mg/Ba = 1:1, rhombohedral norsethite;norsethite; reduced: lenticular = 1:5, lenticular phous aggregates; middle: Mg/Ba = 1:1, rhombohedral reduce: Mg/Ba = 1:five, Mg/Ba witherite). witherite).4. Discussion 4.1. Hydration Hindrance Two observations stand out distinctively in the aqueous experiments. (1) DMPO supplier Incongruent crystallization ([Mg/Ca]solid/[Mg/Ca]solution 1) occurred for exclusive norsethite formation because the solutions had been expected to possess a lot more Mg than Ba with an observed minimal worth of Mg/Ba 7/3, and (two) norsethite was in no way detected in options with Mg/Ba 6/4,Minerals 2021, 11,8 of4. Discussion four.1. Hydration Hindrance Two observations stand out distinctively from the aqueous experiments. (1) Incongruent crystallization ([Mg/Ca]solid /[Mg/Ca]solution = 1) occurred for exclusive norsethite formation because the solutions had been needed to possess a lot more Mg than Ba with an observed minimal worth of Mg/Ba 7/3, and (2) norsethite was never ever detected in options with Mg/Ba 6/4, whereas witherite could crystallize in Mg2 dominated (as robust as Mg:Ba = 9:1) situations (provided that the cation-to-anion ratio is higher). The requirement of Mg-enriched resolution to precipitate norsethite was observed previously by Lippmann [4] and Hood et al. [36] using a relative abundance of Mg/Ba 1.six although sustaining CO3 2- at a fixed concentration (0.five M). A plausible conclusion we are able to draw from these findings is the fact that the stronger hydration of magnesium (than of Ba2 ) may possibly have restricted Mg2 from being inside the cost-free (dehydrated) state, so much to ensure that 50 a lot more Mg2 was required to match the quantity of totally free Ba2 ions within the options. In the opposite end, even though witherite appeared to type a lot more simply within the Mg a O2 two O method provided that the logW is smaller sized all through the experiments by a aspect of 20 in comparison with logN , norsethite nonetheless crystallizes readily and may usually be the exclusive precipitate at distinct situations (Mg/Ba 7/3, cation/anion 60). Aqueous crystallization of norsethite at ambient circumstances is recognized all along [4,35,38,45,46] but isn’t known to call for more energy input besides supersaturation, and thus, it can be inconsistent with the view that Mg2 two O interactions act as a barrier to stopping magnesium ions from getting into the rhombohedral carbonate lattice. Contrasting using the Mg-ri.