Development and Application of ReaxFF Methodology for Understanding the Chemical Dynamics of Metal Carbonates in Aqueous Solutions

A new ReaxFF reactive force field has been developed for metal carbonate systems including Na+, Ca2+, and Mg2+ cations and the CO32- anion. This force field is fully transferable with...

The Application of Thermal Decomposition for Determination of Carbonate Acid-Neutralising Capacity for Improved Acid Mine Drainage Prediction

This study developed an industry-applicable, thermal decomposition methodology for quantification of carbonate mineral acid neutralisation capacity (ANCtherm-carb) for waste rock, tailings, and other mined materials. Standard titration-based methods for ANC can be compromised due to contributions from silicate minerals, ion exchange, Fe-rich carbonates, and other transition metal carbonates. C emission (CO2 and CO) was measured using IR in a N2 atmosphere. Cneut (wt%) was calculated using the C emission at 800 or 1000 °C minus the C emission at 400, 450 or 500 °C and the weight of sample prior to decomposition (Equation (2) of this manuscript). This value was then input into Equation (3) of this manuscript to calculate ANCtherm-carb. Good correlation of ANCtherm-carb for single-mineral carbonates with ANCcalc, calculated from bulk assay concentrations for Mg, K, Na, Ca, and Mn, was achieved. Thereafter, 18 waste rock samples were examined, resulting in the correlation of ANCtherm-carb versus non-standard ANCtitrate-carb (titration methodology adapted to focus on carbonate neutralisation only) with R2 = 0.96. This correlation is valid for samples containing both non-neutralising carbonates (siderite) and sources of neutralisation arising from non-carbonates (Mg-clay) within this waste rock system. Typically, mining operations use total C measurements for assessment of carbonate neutralisation potential in the block and mining model. This method provides an effective means to cheaply analyse for carbonate neutralisation potential with assignment of potentially acid-forming and non-acid-forming blocks to waste rock cells, etc.

Formation and Transformation Trends of Metal Carbonates With Cation Ratio and Ion Interaction in Post-treatment Process of Desalination Brine

BackgroundTo address the negative effects of desalination plants, CO2 emissions, and discharge of desalination brine, we studied the carbon capture utilization (CCU) process based on metal carbonation via the reuse of desalination brine. In this study, we converted CO2 and simulated desalination brine into metal carbonate using monoethanolamine as an aqueous absorbent. The produced metal carbonate varied according to the cation component of the simulated desalination brine. We focused on ion interactions in the aqueous system, occurred by cation ratio, and other phenomena caused by the interactions.ResultsWe determined that the common ion effect, which occurred owing to the ion interactions of the system, was the main reason for the various carbonation trends. Ionic atmospheres that were changed by the ionic components significantly affected the trends. The high salinity of the desalination brine also affected the metal carbonation. We further deduced that the variation in the results was derived from interactions between the abovementioned effects. And we also found that Na+, which was overlooked in former studies about polymorph transformation, also affects polymorph transformation.ConclusionsAll the phenomena in the metal carbonation interrupt desalination brine post-treatment because of their unpredictability. However, we suggest ambient estimation of its cation components, which would help future studies and demonstrate desalination brine post-treatment.

The Pb-Zn (Ba) Nonsulfide Mineralizations at Bou Caïd (Ouarsenis, Algeria): Mineralogy, Isotope Geochemistry, and Genetic Inferences

The ore deposits of Bou Caïd (Ouarsenis, Algeria) occur in Jurassic and Cretaceous sedimentary rocks. The barite and Pb-Zn (Fe, Cu, and F) ore deposits of Bou Caïd belong to vein- and karst-type. The mineralization is represented in the whole area by a mixture of barite (currently still exploited) and nonsulfides consisting of hemimorphite, smithsonite, cerussite, hydrozincite, and Fe-oxy-hydroxides, with remnants of galena and sphalerite in variable proportions. Mineralogical and geochemical analyses were carried out on the Bou Caïd nonsulfides. Several samples representing nonsulfide mineralization (Grand Pic and at Srâa Abdelkader) were subjected to a multidisciplinary analytical approach, using optical microscopy (OM), powder X-ray diffraction (PXRD), Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS). Nonsulfide mineralization consists of a mixture of hemimorphite, hydrozincite, smithsonite, cerussite, and Fe-oxy-hydroxides, often with zebra-like textures. In the proposed paragenetic scheme, covellite and chalcocite are followed by cerussite, jarosite, smithsonite, and hydrozincite. Then, hemimorphite crystallizes, accompanied by mimetite, traces of malachite and clay minerals (also Zn-bearing), precipitate. Fe-(Mn)-oxy-hydroxides can form during various phases of the supergene stage. Small amounts of late barite can be related to partial remobilization and occur as reprecipitation products. Stable isotope analyses were performed on the calcites and metal carbonates of the supergene ores. Carbon and oxygen isotope values of smithsonite and hydrozincite were comparable to published supergene Zn carbonate data. The isotope values of the Bou Caïd calcites fell both into the hydrothermal carbonate and in the supergene fields.

Water mediated growth of oriented single crystalline SrCO3 nanorod arrays on strontium compounds

Morphology-controlled strontianite nanostructures have attracted interest in various fields, such as electrocatalyst and photocatalysts. Basic additives in aqueous strontium solutions is commonly used in controlling strontianite nanostructures. Here, we show that trace water also serves an important role in forming and structuring vertically oriented strontianite nanorod arrays on strontium compounds. Using in situ Raman spectroscopy, we monitored the structural evolution from hydrated strontium to strontianite nanorods, demonstrating the epitaxial growth by vapor–liquid–solid mechanism. Water molecules cause not only the exsolution of Sr liquid droplets on the surface but also the uptake of airborne CO2 followed by its ionization to CO32−. The existence of intermediate SrHO+–OCO22− phase indicates the interaction of CO32− with SrOH+ in Sr(OH)x(H2O)y cluster to orient strontianite crystals. X-ray diffraction simulation and transmission electron microscopy identify the preferred-orientation plane of the 1D nanostructures as the (002) plane, i.e., the growth along the c-axis. The anisotropic growth habit is found to be affected by the kinetics of carbonation. This study paves the way for designing and developing 1D architecture of alkaline earth metal carbonates by a simple method without external additives at room temperature.

Controlled Synthesis of BaCO3 Microstructures Using Various Natural Gums - A Biomimetic Approach

In this study, Barium carbonate microstructures assembled from nanorods are successfully synthesized at room temperature and screw capped method at 100C. The experiments show that the protocol followed for the synthesis of BaCO3 as well as the concentration of various gums used, play an important role in the size and morphology of BaCO3. Here in, we obtained witherite type nanorods aggregates with unusual morphologies via transformation of metal carbonates at different conditions using natural gums as additives. A rational mechanism based on the oriented self-assembly of BaCO3 nuclei is proposed for the formed architectures. The crystals undergo an interesting morphology changes and have been well characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared spectroscopy (FT-IR) techniques. This method is simple, low-cost and environmentally friendly route for the synthesis of BaCO3 microstructures with altogether different morphologies.