Galvanic replacement is a versatile approach to prepare hollow nanostructures with controllable morphology and elemental composition. The primary issue is to identify its fundamental mechanism. In this study, in situ liquid cell transmission electron microscopy was employed to monitor the dynamic reaction process and to explore the mechanism of galvanic replacement. The detailed reaction process was revealed based on in situ experiments in which small Au particles first appeared around Ag nanowires; they coalesced, grew, and adhered to Ag nanowires. After that, small pits grew from the edge of Ag nanowires to form tubular structures, and then extended along the Ag nanowires to obtain hollowed structures. All of our experimental observations from the viewpoint of electron microscopy, combined with DFT calculations, contribute towards an in‐depth understanding of the galvanic replacement reaction process and the design of new materials with hollow structures.

This study presents a novel technology, termed thermomorphic hydrophilicity base-induced precipitation (THBIP), for the effective removal of hardness ions from hypersaline brines with high-scaling propensity. THBIP utilizes thermoresponsive amine bases for the controlled precipitation of scaling constituents in alkaline conditions and subsequently uses low-temperature heat to trigger the phase separation of amine from aqueous solution, thus enabling reuse of the base. Three amines exhibiting distinct water solubility and basicity, specifically, diisopropylamine (DIPA), N-ethylcyclohexylamine (ECHA), and N,N-dimethylisopropylamine (DMIPA), were examined to identify the key parameters affecting THBIP performance. The amine bases were added to solutions containing hardness ions, Mg2+ or Ca2+, to induce the precipitation of hydroxide minerals (i.e., Mg­(OH)2(s) and Ca­(OH)2(s)). All three amines are effective in increasing solution pH, leading to high Mg2+ removals of over 90%. But because Ca­(OH)2(s) is relatively more soluble, only DIPA, which is both highly miscible in water and also the strongest base, obtained significant removal of Ca2+ ions (>33%). The observed precipitation and hardness removal are quantitatively consistent with the principles of aqueous chemistry. Using a simulated hypersaline feedwater (240 g/L total dissolved solids) of high-scaling propensity, THBIP with DIPA achieved ∼80% hardness removal. Subsequent elevation of the temperature from 15 to 70 °C triggered demixing of the thermoresponsive base from the aqueous solution, to enable liquid–liquid separation for amine reuse. The study demonstrates the proof-of-concept of using thermomorphic hydrophilicity bases as an alternative strategy to effectively reduce the scaling potential of hypersaline brines.

No abstract

In this study, we employed in-situ liquid cell transmission electron microscopy (LC-TEM) to carry out the new design strategy of precisely regulating the microstructure of large-sized cocatalysts for highly efficient...

No abstract