33 research outputs found
GaMin’11 – an International Inter-laboratory Comparison for Geochemical CO2 - Saline Fluid - Mineral Interaction Experiments
Due to the strong interest in geochemical CO2-fluid-rock interaction in the context of geological storage of CO2 a growing number of research groups have used a variety of different experimental ways to identify important geochemical dissolution or precipitation reactions and – if possible – quantify the rates and extent of mineral or rock alteration. In this inter-laboratory comparison the gas-fluid-mineral reactions of three samples of rock-forming minerals have been investigated by 11 experimental labs. The reported results point to robust identification of the major processes in the experiments by most groups. The dissolution rates derived from the changes in composition of the aqueous phase are consistent overall, but the variation could be reduced by using similar corrections for changing parameters in the reaction cells over time. The comparison of experimental setups and procedures as well as of data corrections identified potential improvements for future gas-fluid-rock studies
Neutron reflection study of the adsorption of the phosphate surfactant NaDEHP onto alumina from water.
The adsorption of a phosphorus analogue of the surfactant AOT, sodium bis(2-ethylhexyl) phosphate (NaDEHP), at the water/alumina interface is described. The material is found to adsorb as an essentially water-free bilayer from neutron reflection measurements. This is similar to the behavior of AOT under comparable conditions, although AOT forms a thicker, more hydrated layer. The NaDEHP shows rather little variation with added salt, but a small thickening of the layer on increasing the pH, in contrast to the behavior of AOT.We thank BP plc and EPSRC for financial support for this work as well as the ISIS and ILL staff and scientists for the allocation of beam time and technical assistance with NR measurements. We also appreciate Chris Sporikou at Department of Chemistry, University of Cambridge, for help with the surfactant synthesis.This is the final version of the article. It first appeared at http://dx.doi.org/10.1021/la504837
Determination of Rare Earth Elements in Hypersaline Solutions Using Low-Volume, Liquid–Liquid Extraction
Complex, hypersaline brines–including those coproduced with
oil and gas, rejected from desalination technologies, or used as working
fluids for geothermal electricity generation–could contain
critical materials such as the rare earth elements (REE) in valuable
concentrations. Accurate quantitation of these analytes in complex,
aqueous matrices is necessary for evaluation and implementation of
systems aimed at recovering those critical materials. However, most
analytical methods for measuring trace metals have not been validated
for highly saline and/or chemically complex brines. Here we modified
and optimized previously published liquid–liquid extraction
(LLE) techniques using bisÂ(2-ethylhexyl) phosphate as the extractant
in a heptane diluent, and studied its efficacy for REE recovery as
a function of three primary variables: background salinity (as NaCl),
concentration of a competing species (here Fe), and concentration
of dissolved organic carbon (DOC). Results showed that the modified
LLE was robust to a range of salinity, Fe, and DOC concentrations
studied as well as constant, elevated Ba concentrations. With proper
characterization of the natural samples of interest, this method could
be deployed for accurate analysis of REE in small volumes of hyper-saline
and chemically complex brines
Rare Earth Element Distributions and Trends in Natural Waters with a Focus on Groundwater
Systematically varying properties
and reactivities have led to
focused research of the environmental forensic capabilities of rare
earth elements (REE). Increasing anthropogenic inputs to natural systems
may permanently alter the natural signatures of REE, motivating characterization
of natural REE variability. We compiled and analyzed reported dissolved
REE concentration data over a wide range of natural water types (ground-,
ocean, river, and lake water) and groundwater chemistries (e.g., fresh,
brine, and acidic) with the goal of quantifying the extent of natural
REE variability, especially for groundwater systems. Quantitative
challenges presented by censored data were addressed with nonparametric
distributions and regressions. Reported measurements of REE in natural
waters range over nearly 10 orders of magnitude, though the majority
of measurements are within 2–4 orders of magnitude, and are
highly correlated with one another. Few global correlations exist
among dissolved abundance and bulk solution properties in groundwater,
indicating the complex nature of source-sink terms and the need for
care when comparing results between studies. This collection, homogenization,
and analysis of a disparate literature facilitates interstudy comparison
and provides insight into the wide range of variables that influence
REE geochemistry
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CO2-rock-brine interactions in Lower Tuscaloosa Formation at Cranfield CO2 sequestration site, Mississippi, U.S.A.
Bureau of Economic Geolog
Effects of Ligand Chemistry and Geometry on Rare Earth Element Partitioning from Saline Solutions to Functionalized Adsorbents
Rare earth elements
(REE) are elements that drive the development
of new technologies in many sectors, including green energy. However,
the supply chain of REE is subject to a complex set of technical,
environmental, and geopolitical constraints. Some of these challenges
may be circumvented if REE are recovered from naturally abundant alternative
sources, such as saline waters and brines. Here, we synthesized and
tested aminated silica gels, functionalized with REE-reactive ligands:
diethylenetriaminepentaacetic acid (DTPA), diethylenetriaminepentaacetic
dianhydride (DTPADA), phosphonoacetic acid (PAA), and N,N-bisphosphonoÂ(methyl)Âglycine
(BPG). A suite of characterization techniques and batch adsorption
experiments were used to evaluate the properties of the functionalized
silica adsorbents and test the REE-uptake chemistry of the adsorbents
under environmentally relevant conditions. Results showed that BPG
and DTPADA yielded the most REE-reactive adsorbents of those tested.
Moreover, the DTPADA adsorbents demonstrated chemical and physical
robustness as well as ease of regeneration. However, as in previous
studies, amino-polyÂ(carboxylic acid) adsorbents showed limited uptake
at midrange pH and low-sorbate concentrations. This work highlighted
the complexity of intermolecular interactions between even moderately
sized reactive sites when developing high-capacity, high-selectivity
adsorbents. Additional development is required to implement an REE
recovery scheme using these materials; however, it is clear that BPG-
and DTPADA-based adsorbents offer a highly reactive adsorbent warranting
further study