Evaluating the Impact of Tailored Water Wettability on Performance of CO₂ Capture

Abstract

The growing emission of CO 2 is a severe cause of concern due to its adverse impact on the environment and climate change worldwide. In the past, various approaches, including synthesis of porous materials and amino modifications, were adopted for efficient and direct separation of CO 2 from flue gas. Recently, hydrophobicity has been introduced to protect some of the highly potent porous materials and membranes from high humidity and aqueous exposures. While these approaches remained successful in removing CO 2 from flue gas, the exact role of hydrophobicity towards CO 2 separation is not yet validated in the literature. In this current study, an amine-amplified chemically reactive coating on fibrous cotton has been unprecedentedly developed for facile tailoring of different water wettability through the 1,4-conjugate addition reaction under ambient conditions. Further, these amine-amplified interfaces having tailored water wettability were extended to investigate independently the role of: (a) amine amplification and (b) hydrophobicity on the performance of CO 2 separation at room temperature and atmospheric pressure. The increased hydrophobicity on the amine-amplified interface played an important role in improving the CO 2 uptake from 24 mmol/L (water contact angle (WCA) of 86°) to 63 mmol/L (WCA of 151°). However, superhydrophobic coating that lacked the amine amplification process displayed a poor (7 mmol/L) CO 2 separation performance. Thus, controlled amalgamation of amine amplification and bioinspired superhydrophobicity in fibrous cotton lead to a synergistic impact towards efficient CO 2 separation at ambient temperature and pressure, irrespective of the level of humidity present during the course of the experiments. Thus, this current study would allow to design a more potent CO 2 removal material by strategic association of porosity, amine modulation, and liquid wettability.

Understanding the Effect of Water on CO2 Adsorption

“…Such materials would reduce water uptake/working capacity, while improving the stability of amine sites toward leaching and surface mobility. Several adsorbents, consisting of either a hydrophobic support , or hydrophobic organic moieties , with improved behavior in the presence of moisture, were reported in the literature. Guo et al used an amine-tethered polymer synthesized by copolymerization of glycidyl methacrylate, tert -butyl methacrylate, and trimethylolpropane triacrylate into microporous hydrophobic beads, followed by covalent immobilization of TEPA via epoxy groups.…”

Michael Addition Reaction Assisted Derivation of Functional and Durable Superhydrophobic Interfaces

“…Thereafter, Rather et al introduced amine amplified superhydrophobicity on cotton, where the residual chemical reactivity of CRPNC derived coating on cotton was covalently used to integrate BPEI, prior to modification with octadecylaminefollowing Michael addition reaction at ambient conditions. 68 Thereafter, the amine amplification aided in carbon dioxide capture through the formation of carbamic acids while the remaining acrylates were postmodified with increasing hydrophobic amine small molecules to evaluate the impact of water wettability on the carbon dioxide capture. It was concluded that "amine amplified" superhydrophobicity exhibited superior carbon dioxide capture in comparison to just a superhydrophobic substrate at practically harsh and diverse settings.…”

“…Such characteristics are of utmost importance for realistic and diverse applications of the bioinspired coating. In this regard, the environment-friendly Michael addition reaction between amine and acrylate requiring mild operational conditions would provide a prospective platform to tailor the bioinspired water wettability and other relevant physical properties (Figure )including transparency, mechanical property, porosity, etc.following simple and scalable fabrication processes. − In the past, the catalyst-free Michael addition reaction was successfully extended to produce amplified “reactive” surfaces. , Ford et al studied the ability of growing different nanostructures on selected substrates following the catalyst-free aza-Michael addition reaction between branched polyethylenimine (BPEI) and dipentaerythritol penta-acrylate (5-Acl) that resulted in hyperbranched poly­(ester amines) cross-linked thin films with surface amplified functional groups . In 2012, Bechler et al capitalized on this concept of a nanostructured, “reactive” polymeric film of BPEI/5Acl to construct a relatively thick (∼750 nm) multilayer coating following the layer-by-layer deposition approach .…”

“…The research group of Manna et al introduced and extended these solution phase CRPNCs for developing porous, three-dimensional superhydrophobic monoliths and flexible polymeric superhydrophobic coatings for applications in oil/water separation, ,,− ,,− ,, drug delivery, ,, patterned interfaces, ,,, etc. The controlled growth of CRPNCs through Michael addition reaction and its strategic postcovalent modifications allowed different durable bioinspired wettabilities to be adoptedincluding controllable adhesive/nonadhesive superhydrophobicity, hydrophilic/superhydrophobic patterns, chemically “reactive” superhydrophobicity, and stimuli-responsive superhydrophobicityfollowing simple and scalable fabrications processes. − The as fabricated chemically “reactive” interfaces with tailorable water wettability exhibited impeccable durability and performance at even chemically harsh and challenging settings. The strategic use of the catalyst-free Michael addition reaction allowed the successful modulation of mechanical property, porosity, shrinkage, optical transparency, etc.…”

“…Apart from the Michael addition reaction stimulated sol–gel conversion approach, CRPNCs were utilized for coating on various large and geometrically complex objects following accelerated layer-by-layer deposition, dip coating, − and spray deposition processes. Prior to the gelation of the reaction mixture, the growing dispersions of CRPNCs in ethanol were strategically exploited to dip coat a wide range of commercially available porous and fibrous substrates for application in selective and repetitive both absorption-based and gravity-driven filtration-based oil/water separation, − sustained drug delivery, carbon dioxide capture, etc. The presence of the micro/nanosized “reactive” nanocomplexes on individual fibers of the substrates imparted the essential topography and scope for postfunctionalization with amine-containing small molecules to exhibit different bioinspired water wettabilities.…”