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In previous work, it has been shown that a deep eutectic mixture (DEM) of choline chloride and urea facilitates the detachment of bitumen from oil sands. To probe the mechanism underlying this observation, adhesive forces at the surface of the bitumen samples in deionized water and this DEM are compared using atomic force microscopy. PeakForce Tapping mode was used for force–distance measurement. Silicon nitride tips with dimensions of the order of 20 nm and silica colloidal particle attached probes with diameters of the order of 40 μm were used. For both AFM probes, the adhesion force between the probe tip and the bitumen surface decreased significantly with increasing DEM concentration, as did the dissipation energy.

Rare earth elements are known to occur in low concentrations in U.S. coals and coal byproducts. These low concentrations may make rare earth element recovery from these materials unattractive, using only physical separation techniques. However, given the significant production of rare earths through ion exchange extraction in China, two U.S. coal byproducts were examined for ion extraction, using ammonium sulfate, an ionic liquid, and a deep eutectic solvent as lixiviants. Extraction of rare earth elements in each case produced high recoveries of rare earth elements to the solution. This suggests that in at least the cases of the materials examined, U.S. coal byproducts may be technically suitable as REE ores. More work is required to establish economic suitability.

It is well-known that dispersing catalysts to obtain good contact with coal particles enhances coal liquefaction. This is often accomplished using soluble catalyst precursors that are then converted to an active form. In this study, it is shown that certain ionic liquids can be used to fragment, disperse, and partially dissolve coal to such an extent that good contact can be made with commercially obtained, micrometer-size molybdenum disulfide particles by simply mixing these particles with the ionic liquid/coal dispersion. Good liquefaction yields under standard conditions are obtained using this approach.

In “good” solvents such as pyridine, coal particles swell and fracture to some degree as soluble material is extracted, but they remain as more-or-less coherent particles. It is shown here that certain ionic liquids (ILs) are capable of solubilizing, disintegrating, and dispersing certain coals as very fine particles to a remarkable extent. The solubility of two coals, a Powder River Basin coal and an Illinois No. 6 coal, also increased significantly in IL/N-methyl pyrrolidinone (NMP) and IL/pyridine mixtures, relative to the solubility of the coals in NMP and pyridine. A third coal, Upper Freeport, gave yields that were lower than those obtained in pyridine alone. This coal may be anomalous in its behavior. It is suggested that many if not most coals are densely cross-linked networks where a portion of soluble material remains trapped, even upon swelling in good solvents, which fracture and only partially fragment coals at ambient temperatures. Certain ILs fragment and disperse some coals to a much great...