A first‐principles approach for treating wastewaters

Abstract

Numerous materials are employed for the removal of contaminants from wastewaters. However, the regeneration/reuse of these materials is still seldom practiced. Quantitative insights into intermolecular forces between the contaminants and the functional surfaces might aid the rational design of reusable materials. Here, we compare the efficacies of aliphatic (C8H18), aromatic (C6H6), and aromatic perfluorinated (C6F6) moieties at removing methylene blue (MB+) as a surrogate cationic dye from water. We employed density functional theory with an implicit polarizable continuum model for water to accurately determine the contributions of the solvent's electrostatics in the adsorption process. Our calculations pinpointed the relative contributions of ππ stacking, van der Waals complexation, hydrogen bonding, and cationπ interactions, predicting that MB+ would bind the strongest with C6F6 due to hydrogen bonding and the weakest with C8H18. Complementary laboratory experiments revealed that, despite the similar hydrophobicity of silica beads functionalized with SiC8H17, SiC6H5, and SiC6F5 groups, as characterized by their water contact angles, the relative uptake of aqueous MB+ varied as SiC6F5 (95%) > SiC6H5 (35%) > SiC8H17 (3%). This first principles‐led experimental approach can be easily extended to other classes of dyes, thereby advancing the rational design of adsorbents.

Zwitterions Layer at but Do Not Screen Electrified Interfaces

“…Ions and zwitterions orchestrate the inner workings of prokaryotic, plant, and animal cells via electromagnetic interactions, thereby giving rise to finely tuned structure–function relationships in proteins, chemical reactions, catalysis, molecular recognition and signaling, and bioenergetics. − Ion electrostatics is also relevant in numerous environmental and industrial contexts, including cloud acidification, , soil water-holding capacity, microdroplet chemistry, − stability of pharmaceutical and cosmetic formulations, water desalination and treatment processes, and harvesting nanotriboelectricity . Interestingly, simple hard ions, such as Na + , K + , Mg 2+ , Ca 2+ , and Cl – , which are ubiquitous in biological systems, retain their electrical charge irrespective of the solution pH or temperature .…”

Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make‐Up, Hydrostatic Pressure, and Cavity Aspect Ratio

“…Thus, significant deviation from the common advancing/receding behavior of water on a smooth FDTS-coated surface is expected. [9] Lastly, there was a significant deviation in our predictions and the experimental observations for the experiments conducted at lower hydrostatic pressures, namely, 50-60 kPa ( Figure 10F,I). This was due to the fact that our model does not include the effects of capillary condensation, which plays a major role at lower pressures.…”

“…Building upon previous reports on the diffusion of the air entrapped inside cavities submerged in liquids, [9,[55][56][57] we developed a 1-D model to gain insights into our experimental results. Previous reports, however, did not consider the effects of the pressure during the ramp-up phase.…”

“…[7] These specialized surfaces are typically realized by coating rough or micropatterned surfaces with water-repellent chemicals, commonly perfluorocarbons. [8,9] However, the cost and environmental impact [10] of these coatings, along with their vulnerability to organic fouling, [11] long-term immersion in water, [12,13] heat and chemicals, [14] and abrasion [15] limit their aspect ratio-and the chemical make-up of the surface. [25,[35][36][37][38][39] Thus, for the coating-free approach to be practical, clear insights into the factors and mechanisms that govern the kinetics of Cassie-to-Wenzel transitions are crucial.…”

“…[25,[35][36][37][38][39] Thus, for the coating-free approach to be practical, clear insights into the factors and mechanisms that govern the kinetics of Cassie-to-Wenzel transitions are crucial. While wetting transitions in coating-based water-repellent microtextures have been explored extensively, [9,[40][41][42][43][44][45][46] insights into wetting transitions in coating-free microtextures (DRCs) are largely obscure. In particular, the effects of hydrostatic pressure on wetting transitions have not been explored, despite their obvious practical relevance, for instance, in pipe-flows and marine applications.…”