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Herein, we investigated the effects of mixed collectors with varying alkyl chain lengths and ligand types on the hydrophobicity of the spodumene–feldspar flotation system. Various collector–mineral interactions were compared using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with two-dimensional correlation spectroscopy (2D-COS), in situ microcalorimetry, and X-ray photoelectron spectroscopy (XPS). The highest flotation separation performance can be achieved at a molar ratio of 6:1 and pH 8–9. The in situ microcalorimetry results revealed that the difference in the adsorption reaction heat of the mixed collector is larger than that of the single anionic collector. Moreover, the inconformity between the magnitude of adsorption reaction heat and the results observed for flotation recovery indicates that the heat of the reaction presumably involves the adsorption configurations of the collectors and the amounts adsorbed. In in situ ATR-FTIR with 2D-COS, it can be observed that octanohydroxamic acid/dodecylamine (OHA/DDA) is adsorbed much more intensely onto feldspar than onto spodumene due to the availability of more space on feldspar for the subsequent sorption of DDA after the prior bidentate chemisorption of OHA under alkaline conditions, whereas the sodium oleate (NaOL)/DDA adsorption sequence at pH 4–5 was the reverse of that at pH 8–9. Lastly, XPS was employed to provide further supplemental evidence for the bonding between these two minerals and single anionic/mixed collectors at the optimal pH of 8–9. In this study, the powerful in situ detection technologies can establish a new platform for exploring the underlying mechanism of new reagents at the solid–liquid interface. Moreover, the in-depth understanding related to the adsorption behavior of the mixed collector is beneficial for facilitating the selection and design of efficient and environmentally friendly flotation collectors with improved selectivity.

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Humic acid (HA) is ubiquitous in both terrestrial and aquatic environments, and understanding the molecular interaction mechanisms underlying its aggregation and adsorption is of vital significance. However, the intermolecular interactions of HA−HA and HA−clay mineral systems in complex aqueous environments remain elusive. Herein, the interactions of HA with various model surfaces (i.e., HA, mica, and talc) were quantitatively measured in aqueous media at the nanoscale using an atomic force microscope. The HA−HA interaction was found to be purely repulsive during surface approach, consistent with free energy calculation; during retraction, pH-dependent adhesion was observed due to the protonation/ deprotonation of HA that influences the formation of hydrogen bonds. Different from the mica case, hydrophobic interaction was detected for the HA−talc system at pH 5.8, contributing to the stronger HA−talc adhesion, as also evidenced by adsorption results. Notably, HA−mica adhesion strongly depended on the loading force and contact time, most likely because of the short-range and time-dependent interfacial hydrogen bonding interaction under confinement, as compared to the dominant hydrophobic interaction for the HA−talc case. This study provides quantitative insights into the fundamental molecular interaction mechanisms underlying the aggregation of HA and its adsorption on clay minerals of varying hydrophobicity in environmental processes.

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Geological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly accepted sense, considered as the most promising and powerful approach to mitigate the global carbon emissions during the transition to net‐zero. Of the geological media which initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts, up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, two tandem papers propose novel strategies for the first time, by synthesizing and utilizing new high‐dryness CO2 foam, to enhance geological CO2 storage capacity in saline aquifer and oil and gas reservoirs. In this paper, a new high‐dryness CO2 foam is synthesized and injected into the saline aquifers to explore the storage capacity enhancement, with the unique foam‐induced advantages of sweep area expansion and storage efficiency improvement. Such a new idea is specifically evaluated and validated through a series of static analytical and dynamic performance experiments. With the optimum surfactant concentration of 0.5 wt%, the foaming volume and quality are determined to be 521 mL and 80.81%, respectively, which also shows excellent salt tolerance with 45,000 ppm Na+, 25,000 ppm Ca2+, and 25,000 ppm Mg2+. Moreover, the water consumption for CO2 storage decreases from 464.31 g/mol at 25% foam quality to 67.38 g/mol at 85% foam quality by using the new CO2 foam. Overall, the newly synthesized CO2 foam could effectively enhance geological CO2 storage capacity and concurrently diminish water consumption, therefore realizing the win‐win environment and economic benefits.