Effect of Solution Silicate on the Precipitation of Barium Sulfate

The presence of silicate during barium sulfate crystallization has different impacts depending on the pH of the solution. At pH 7 the dominance of the protonated form (H₄SiO₄) and possible polymerization of the silicate impacts mainly on the aggregation state and on twinning of the barium sulfate formed. At higher pH values (∼10), the silicate ion present is able to influence both morphology and partially substitute for sulfate in the lattice. Interesting fibrous particles are formed under these conditions, but this is not due to mesocrystal formation as the particles are observed to be single crystalline in nature. These fibrous sections are found to be dominant on the surface and are highly porous. These particles are different, however, to the biomorphs formed when crystallization of barium carbonate occurs in the presence of silicate. This is because the speciation of sulfate does not change over a large pH range. The impact of silicate on barium sulfate particles is similar to the impact on calcium carbonate and strontium sulfate crystallization

The Impact of Sugars on Kidney Stone Formation

Various studies have found a trend connecting diabetes mellitus or carbohydrate malabsorption syndromes to kidney stone formation. However, the underlying mechanism causing this impact is unclear. This study aimed to investigate whether some of this correlation is due to the underlying chemistry of sugars as crystal growth modifiers. Thus, the impact of major dietary monosaccharides (glucose, fructose, and galactose) and disaccharides (lactose and sucrose) on the formation of calcium oxalate was investigated from a crystallization perspective. The nucleation rate of calcium oxalate generally showed a promotion when monosaccharides were present. An analysis of the crystals with Raman spectroscopy found that signals for the monosaccharides are present within the crystal, showing an association between the sugars and calcium oxalate. When lactose was present, there was an obvious promotion of nucleation. When sucrose was present, an interaction with both the crystal and the solution ions was observed. The presence of galactose had the most influence on the zeta potential of calcium oxalate when zinc ions were present, resulting in the smallest zeta potential value. These results suggest that the sugars in urine may promote calcium oxalate formation and agglomeration, and this may suggest a chemical connection to the higher prevalence of stones in diabetic patients

CO₂ and CH₄ Wettabilities of Organic-Rich Shale

CO₂ and CH₄ wettabilities of organic-rich shale are important physicochemical parameters that significantly influence CO₂ sequestration and CH₄ production. However, there is a serious lack of understanding of these aspects because the data available are scarce. Thus, we evaluated organic-rich shale CO₂ and CH₄ wettabilities (i.e., brine/shale/gas systems) through advancing and receding brine contact angle measurements as a function of pressure, temperature, salinity, and ion type (as these can vary significantly in underground formations). The results indicated that the brine contact angles for both CO₂/CH₄–brine–shale systems increased with pressure and salinity, but decreased with temperature. However, these effects were much less significant for CH₄. Furthermore, the brine contact angles for the CO₂–brine–shale system reached 180° (i.e., the shale was completely wetted by CO₂) when the pressure reached 30 MPa at 343 K and ∼9 MPa at 298 K. The brine contact angles for the analogue CH₄ systems was much lower (50°–90°), only indicating weakly water-wet to intermediate-wet conditions. Finally, the brine contact angles for CO₂–brine–shale system were also larger for divalent ions (Ca²⁺, Mg²⁺) than for monovalent ions (Na⁺, K⁺), while ion type had no significant influence on CH₄ wettability. However, a similar CO₂/CH₄ density resulted in a similar wettability. Consequently CH₄ could not be used as a proxy for predicting CO₂ storage capacities, unless they have similar densities