Metals Coprecipitation with Barite: Nano-XRF Observation of Enhanced Strontium Incorporation

Abstract

Coprecipitation can be an effective treatment method for the removal of environmentally relevant metals from industrial wastewaters such as produced waters from the oil and gas industry. The precipitation of barite, BaSO 4 , through the addition of sulfate removes barium while coprecipitating strontium and other alkaline earth metals even when these are present at concentrations below their solubility limit. Among other analytical methods, X-ray fluorescence (XRF) nanospectroscopy at the Hard X-ray Nanoprobe (HXN) beamline at the National Synchrotron Light Source II (NSLS-II) was used to quantify Sr incorporation into barite. Thermodynamic modeling of (Ba,Sr)SO 4 solid solutions was done using solid solution-aqueous solution (SS-AS) theory. The quantitative, high-resolution nano-XRF data show clearly that the Sr content in (Ba,Sr)SO 4 solid solutions varies widely among particles and even within a single particle. We observed substantial Sr incorporation that is far larger than thermodynamic models predict, likely indicating the formation of metastable solid solutions. We also observed that increasing barite supersaturation of the aqueous phase led to increased Sr incorporation, as predicted by available kinetic models. These results suggest that coprecipitation offers significant potential for designing treatment systems for aqueous metals' removal in desired metastable compositions. Solution conditions may be optimized to enhance the incorporation of Sr by increasing sulfate addition such that the barite saturation index remains above *3 or by increasing the aqueous Sr to Ba ratio.

Studies of Mineral Nucleation and Growth Across Multiple Scales: Review of the Current State of Research Using the Example of Barite (BaSO4)

“…With regards to kinetics, at higher supersaturations and hence faster growth rates, the dependence of the distribution coefficient on the growth rate is not straightforward due to kinetic effects related to the large changes in reaction rate due to supersaturation . In experimental studies, solid solution compositions ranging from Sr-rich to Ba-rich solid solution have been observed to precipitate from the same source solution. , Similar observations were made when analyzing strontium-containing barite scales from a hydrothermal power plant . Even at low supersaturations (SI = 0.5), a bimodal behavior was observed with a direct correlation of aqueous Sr/Ba ratios to solid Sr/Ba ratios for low aqueous Sr 2+ concentration, but with a solid composition independent of changes in the solution at high supersaturations .…”

“…On a fundamental scientific basis, a mechanistic understanding of metal partitioning during coprecipitation from high salinity solutions at high supersaturations needs to be improved for accurate prediction of contaminant removal though blending of AMD with flowback waters. This is documented in recent studies − where the removal of strontium and arsenic from solution by coprecipitation with barite was investigated and quantified via novel synchrotron-based X-ray fluorescence methods.…”

“…Experimental studies demonstrate sulfate minerals can incorporate a variety of potentially harmful elements, either via thermodynamically driven uptake in the form of a solid solution at low supersaturations or via coprecipitation at high supersaturations. Barite forms isostructural solid solutions by incorporating radium, ,,,,− selenium, arsenic, strontium, , chromium, , and lead. , On the basis of microscopic and spectroscopic studies, these elements incorporate into the barite lattice rather than simply adsorb to the surface. The cations (Ra 2+ , Pb 2+ , Sr 2+ ) substitute isostructurally for the Ba 2+ cation, whereas the anions (HAsO 4 2– , CrO 4 2– , SeO 4 2– ) substitute for the SO 4 2– ion, thus forming solid solutions.…”

“…The removal of radionuclides, metals and metalloids from solution via coprecipitation has been used by geochemists and chemical engineers to remove contaminants from contaminated groundwaters and wastewaters, e.g., from unconventional gas extraction. ,,, Zinc and cadmium contamination in soil and groundwater have been remediated using phosphate minerals , and coprecipitation of radionuclides with carbonates, sulfates and clay minerals have been considered in nuclear waste repository risk assessments. ,, Due to its low solubility, high specific density and its ability to form solid solutions with a variety of cations and anions, barite is often considered as a host mineral for contaminant removal by coprecipitation. The removal of contaminants from flowback and produced water containing the radionuclide Ra by coprecipitation with barite has been extensively studied. ,,, Furthermore, various experimental studies have investigated the removal of selenite, arsenic, iodate, and strontium via coprecipitation. ,,− …”

Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

“…The review is focused on recent advances in X-ray computed tomography (Noiriel and Daval, 2017;Yuan et al, 2021) and development of pore-scale reactive transport models (Molins et al, 2012;Prasianakis et al, 2020;Soulaine et al, 2021;Yang et al, 2021). In both, experimental and numerical studies it is emphasized that the accurate capture of the fluid-solid interface is extremely important (Hunter et al, 2020;Khatoonabadi et al, 2021;Qin and Beckingham, 2021).…”