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1. The role of alkalinity on metals removal from petroleum produced water by dolomite

   Omar, Khalid; Vilcáez, Javier (January 2024, Applied geochemistry)

   Alkalinity is a critical parameter for describing the composition, pH buffer capacity, and precipitation potential of petroleum produced water (PW). Besides salinity, alkalinity and metal concentrations are generally greater in PW than in freshwater (FW) and seawater. This study presents batch reaction experimental and simulation results showing that the removal of Ba, Sr, and Cd from PW by dolomite is mostly due to sorption reactions, with sorption reactions and thus removal levels being higher for Cd than for Ba and Sr. In contrast, we found that the removal of Pb and As from PW by dolomite is largely due to precipitation and coprecipitation reactions of carbonate minerals on dolomite. Analyses of changes in the morphology as well as in the elemental and mineral composition of dolomite surface, along with pH, alkalinity, and Ba, Sr, Cd, Pb, and As removal measurements using synthetic PW and FW containing high concentrations (∼100 mg/L) of single and mixture toxic metals and metalloids (Ba, Sr, Cd, Pb, and As) at different initial alkalinity and pH conditions, indicate that in addition to salinity, alkalinity and pH generated from the dissolution of dolomite controls the removal of Ba, Sr, Cd, Pb, and As from PW by dolomite. However, we found that their impact is different for each metal in PW and FW. Ba, Sr, and Cd removal by dolomite is 10, 2, and 4 times smaller in PW than in freshwater (FW), respectively. Whereas As removal is practically the same regardless of salinity. Moreover, this study reveals the need of thermodynamic data of complex carbonate minerals formed from the precipitation of Ba, Sr, Cd, Pb, and As to capture the effect of alkalinity on their removal from PW by dolomite. 

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2. Transport of Ba, Sr, Cd, Pb, and As in dolomite saline aquifers injected with petroleum produced water

   Omar, Khalid; Vilcáez, Javier (December 2023, Geoenergy science and engineering)

   Predicting the transport of toxic metals in dolomite saline aquifers where petroleum produced water (PW) is commonly injected is important to prevent underground sources of drinking water contamination. This study presents new experimental results on the degree and impact of precipitation and sorption reactions on the transport of high concentrations of toxic metals (80-100 mg-Ba/L, 80-100 mg-Sr/L, 70-100 mg-Cd/L, 2-100 mg-Pb/L, and 80-100 mg-As/L) in dolomite injected with PW of variable alkalinity (0–200 mg/L), total dissolved solids (1700–77,000 mg/L), and pH (2–7). Changes in the elemental and mineral composition of dolomite surface were measured by BSEs SEM, SEM-EDS, and high-resolution XRD analyses. The results reveal a key role of alkalinity generated from the dissolution of dolomite. We show that a short initial stage where the removal of toxic metals is driven by the initial pH and alkalinity of PW is followed by a prolonged stage where the removal of toxic metals by sorption and precipitation reactions is driven by the alkalinity and pH that results from the kinetic dissolution of dolomite. Precipitated/coprecipitated metals were carbonate minerals reflecting the metal composition of PW. Attained removal levels of tested toxic metals from 1 L of PW using a dolomite core made of 200 g were >90% for Pb, >50% for As, >30% for Cd, and >5% for Ba and Sr. Apparently, the in-situ generation of alkalinity (carbonate ions) and sorption reactions of metals on dolomite catalyzes the precipitation of toxic metals as carbonate minerals. This catalytic effect of dolomite is different with PW and fresh water (FW) of low salinity (NaCl). Precipitation reactions are more prominent with FW than with PW, whereas sorption reactions are more prominent with PW than with FW. 

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3. The Geochemistry of Englacial Brine From Taylor Glacier, Antarctica

   https://doi.org/10.1029/2018JG004411  

   Lyons, W. Berry; Mikucki, Jill A.; German, Laura A.; Welch, Kathleen A.; Welch, Susan A.; Gardner, Christopher B.; Tulaczyk, Slawek M.; Pettit, Erin C.; Kowalski, Julia; Dachwald, Bernd (March 2019, Journal of Geophysical Research: Biogeosciences)

   Abstract Blood Falls is a hypersaline, iron‐rich discharge at the terminus of the Taylor Glacier in the McMurdo Dry Valleys, Antarctica. In November 2014, brine in a conduit within the glacier was penetrated and sampled using clean‐entry techniques and a thermoelectric melting probe called the IceMole. We analyzed the englacial brine sample for filterable iron (fFe), total Fe, major cations and anions, nutrients, organic carbon, and perchlorate. In addition, aliquots were analyzed for minor and trace elements and isotopes including δD and δ¹⁸O of water, δ³⁴S and δ¹⁸O of sulfate,²³⁴U,²³⁸U, δ¹¹B,⁸⁷Sr/⁸⁶Sr, and δ⁸¹Br. These measurements were made in order to (1) determine the source and geochemical evolution of the brine and (2) compare the chemistry of the brine to that of nearby hypersaline lake waters and previous supraglacially sampled collections of Blood Falls outflow that were interpreted asend‐memberbrines. The englacial brine had higher Cl⁻concentrations than the Blood Falls end‐member outflow; however, other constituents were similar. The isotope data indicate that the water in the brine is derived from glacier melt. The H₄SiO₄concentrations and U and Sr isotope suggest a high degree of chemical weathering products. The brine has a low N:P ratio of ~7.2 with most of the dissolved inorganic nitrogen in the form of NH₄⁺. Dissolved organic carbon concentrations are similar to end‐member outflow values. Our results provide strong evidence that the original source of solutes in the brine was ancient seawater, which has been modified with the addition of chemical weathering products. 

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4. DO THE TRACE METAL CONCENTRATIONS IN BARNACLE SHELLS FROM RYE, NYACK, AND PIERMONT VARY?

   https://doi.org/10.1130/abs/2023AM-392524  

   Albin, Jenna; Brenner, Logan; DeBellis, Korie (January 2023, Geological Society of America Abstracts with Programs)

   Brenner, L (Ed.)

   The geochemistry of marine carbonates frequently reflects the environmental factors that influence their growth, such as climate and/or water quality. Barnacles are sessile crustaceans with shells that provide such environmental archiving. The bay barnacle, Amphibalanus improvisus, was found in the Hudson River at Piermont, NY and Nyack, NY and was the most abundant species identified. To expand the geographic perspective, Amphibalanus eburneus and Semibalanus balanoides barnacles were collected in Rye, NY on the Long Island Sound coast. However, this did not permit a perfect comparison as these species were not identified at the Hudson River sites. Barnacle samples were cleaned and organic matter removed with a multi-step process that included a vinegar scrub, short bleach bath, and ultrasonication in milli-Q water. Trace metals in calcium carbonate barnacle shells were analyzed via quadrupole mass spectrometer. The analysis focuses on Mg, Sr, Ba, Na, and Y to Ca ratios. There was geographic variation in barnacle Y/Ca, Ba/Ca, and Na/Ca values. This may indicate that the concentrations of these trace metals in the waters of the three places do vary, suggesting there could be potential to explore these measurements as an environmental proxy. The Mg/Ca and Sr/Ca inter-site variability was more difficult to quantify. Although Mg/Ca and Sr/Ca are known paleothermometers in other archives, more work needs to be done to determine their efficacy in these locations. Ultimately, this preliminary data and assessment shows that these metals can be recorded in barnacle shells and opens the door to future environmental- or climate-proxy development in the Hudson River and Long Island Sound. 

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5. A Hybrid Catalytic Hydrogenation/Membrane Distillation Process for Nitrogen Recovery from Nitrate-Contaminated Waste Ion Exchange Brine

   https://doi.org/10.1016/j.watres.2020.115688  

   Huo, X.; Vanneste, J.; Cath, T.Y.; Strathmann, T.J. (January 2020, Water research)

   Ion exchange is widely used to treat nitrate-contaminated groundwater, but high salt usage for resin regeneration and management of waste brine residuals increase treatment costs and add environmental burdens. Development of palladium-based catalytic nitrate treatment systems for brine treatment and reuse has showed promising activity for nitrate reduction and selectivity towards the N2 over the alternative product ammonia, but this strategy overlooks the potential value of nitrogen resources. Here, we evaluated a hybrid catalytic hydrogenation/membrane distillation process for nitrogen resource recovery during treatment and reuse of nitrate-contaminated waste ion exchange brines. In the first step of the hybrid process, a Ru/C catalyst with high selectivity towards ammonia was found to be effective for nitrate hydrogenation under conditions representative of waste brines, including expected salt buildup that would occur with repeated brine reuse cycles. The apparent rate constants normalized to metal mass (0.30 ± 0.03 mM min−1 gRu−1 under baseline condition) were comparable to the state-of-the-art bimetallic Pd catalyst. In the second stage of the hybrid process, membrane distillation was applied to recover the ammonia product from the brine matrix, capturing nitrogen as ammonium sulfate, a commercial fertilizer product. Solution pH significantly influenced the rate of ammonia mass transfer through the gas-permeable membrane by controlling the fraction of free ammonia species (NH3) present in the solution. The rate of ammonia recovery was not affected by increasing salt levels in the brine, indicating the feasibility of membrane distillation for recovering ammonia over repeated reuse cycles. Finally, high rates of nitrate hydrogenation (apparent rate constant 1.80 ± 0.04 mM min−1 gRu−1) and ammonia recovery (overall mass transfer coefficient 0.20 m h−1) with the hybrid treatment process were demonstrated when treating a real waste ion exchange brine obtained from a drinking water utility. These findings introduce an innovative strategy for recycling waste ion exchange brine while simultaneously recovering potentially valuable nitrogen resources when treating contaminated groundwater. 

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