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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Adsorption of rare earth elements in carboxylated mesoporous carbon

The separation of Rare Earth Elements (REEs) from various non-conventional sources is critically important to maintain the supply–demand balance of REEs in the western world. Here, in this research, we have investigated coal Fly Ash (CFA) as the non-conventional source of REEs. In order to recover REEs, we have synthesized carboxylate-functionalized mesoporous carbon (CMC) to harness the chelation-induced adsorption of REEs. These adsorbents were characterized with pore textural properties, FTIR spectroscopy, and SEM-EDX mapping. In the initial study with single-component La(III) Dy(III) and Lu(III), it was revealed that CMC can adsorb those REEs 2–4 times more than that of pristine mesoporous carbon confirming the effective role of the carboxylate group in the REE separation. Furthermore, the affiliation of the carboxylate group towards heavier REEs (Lu>Dy>La, when present is equal amounts) provides an added benefit of this adsorbent owing to the high demand for heavier REEs in the technology sectors. The leachate solution produced from CFA contained sixteen REEs in the range of 50–200 ppb for most of the REEs. It was revealed that CMC can extract 80–90% of all the REEs thereby further confirming the success of the CMC as an effective REE sorbent. Three successive cycles of adsorption and desorption of REEs with the same CMC revealed the consistent adsorption capacity of REEs. In-situ X-ray Absorption Near Edge Spectroscopy (XANES) analysis confirmed the +3 oxidation states of La, Dy, and Lu within CMC. In-situ Extended X-ray Absorption Fine Structure (EXAFS) analysis revealed the shortening of mean La-O, Dy-O, and Lu-O bond distance by 0.03–0.05 Å thereby confirming the coordination of these REEs with carboxylate groups present on CMC.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2O3 by Materials Project

La2O3 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.37–2.74 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent La3+ atoms to form OLa4 tetrahedra that share corners with six equivalent OLa6 octahedra, corners with six equivalent OLa4 tetrahedra, edges with three equivalent OLa6 octahedra, and edges with three equivalent OLa4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–56°. In the second O2- site, O2- is bonded to six equivalent La3+ atoms to form OLa6 octahedra that share corners with twelve equivalent OLa4 tetrahedra, edges with six equivalent OLa6 octahedra, and edges with six equivalent OLa4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2O3 by Materials Project

La2O3 is Corundum-like structured and crystallizes in the cubic Ia-3 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge and corner-sharing LaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of La–O bond distances ranging from 2.42–2.50 Å. In the second La3+ site, La3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge and corner-sharing LaO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All La–O bond lengths are 2.45 Å. O2- is bonded to four La3+ atoms to form a mixture of distorted edge and corner-sharing OLa4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2O3 by Materials Project

La2O3 is High-temperature superconductor-like structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional and consists of one lanthanum molecule and one LaO3 framework. In the LaO3 framework, La3+ is bonded to six equivalent O2- atoms to form corner-sharing LaO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All La–O bond lengths are 2.29 Å. O2- is bonded in a linear geometry to two equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2O3 by Materials Project

La2O3 crystallizes in the trigonal P321 space group. The structure is three-dimensional. La3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge, face, and corner-sharing LaO6 pentagonal pyramids. There are three shorter (2.46 Å) and three longer (2.47 Å) La–O bond lengths. O2- is bonded in a square co-planar geometry to four equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2O3 by Materials Project

La2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.39–2.87 Å. In the second La3+ site, La3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of La–O bond distances ranging from 2.38–2.85 Å. In the third La3+ site, La3+ is bonded to six O2- atoms to form a mixture of distorted corner and edge-sharing LaO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of La–O bond distances ranging from 2.36–2.67 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four La3+ atoms to form distorted OLa4 trigonal pyramids that share a cornercorner with one OLa6 octahedra, corners with two equivalent OLa5 square pyramids, corners with nine OLa4 tetrahedra, corners with two equivalent OLa4 trigonal pyramids, edges with three equivalent OLa5 square pyramids, and edges with two equivalent OLa4 trigonal pyramids. The corner-sharing octahedral tilt angles are 34°. In the second O2- site, O2- is bonded to five La3+ atoms to form distorted OLa5 square pyramids that share corners with seven OLa4 tetrahedra, corners with two equivalent OLa4 trigonal pyramids, edges with two equivalent OLa6 octahedra, edges with two equivalent OLa5 square pyramids, edges with three OLa4 tetrahedra, and edges with three equivalent OLa4 trigonal pyramids. In the third O2- site, O2- is bonded to four La3+ atoms to form OLa4 tetrahedra that share corners with two equivalent OLa6 octahedra, corners with two equivalent OLa5 square pyramids, corners with four OLa4 tetrahedra, corners with six equivalent OLa4 trigonal pyramids, an edgeedge with one OLa6 octahedra, edges with two equivalent OLa5 square pyramids, and an edgeedge with one OLa4 tetrahedra. The corner-sharing octahedral tilt angles are 15°. In the fourth O2- site, O2- is bonded to four La3+ atoms to form OLa4 tetrahedra that share a cornercorner with one OLa6 octahedra, corners with five equivalent OLa5 square pyramids, corners with four OLa4 tetrahedra, corners with three equivalent OLa4 trigonal pyramids, edges with two equivalent OLa6 octahedra, an edgeedge with one OLa5 square pyramid, and edges with two equivalent OLa4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the fifth O2- site, O2- is bonded to six La3+ atoms to form OLa6 octahedra that share corners with six OLa4 tetrahedra, corners with two equivalent OLa4 trigonal pyramids, edges with two equivalent OLa6 octahedra, edges with four equivalent OLa5 square pyramids, and edges with six OLa4 tetrahedra.

36 MATERIALS SCIENCE↗