The “Pudding Effect” to Promote Solar‐Driving Water Purification

Abstract

The use of solar energy (natural) and synthetic solar absorber hydrogels (SAHs) for purification of brackish water represent a challenge. Here in, this work reports the unexpected effect achieved for water desalination when combining a small content of conducting polymer (CP), poly(3,4‐ethylenedioxythiophene) (PEDOT), doped with poly(styrene sodium sulfonate) (PSS), with a well‐known thermosensitive polymer, poly(N‐isopropylacrylamide) (PNIPAAm). Less than 10% of CP is enough to achieve an evaporation rate of 3.45 ± 0.36 KMH, compared to the gel without the ionic polymer (1.75 ± 0.08 KMH). Furthermore, this work proves that the presence of alginate polysaccharide (ALG), which is a conventional reinforcement molecule applied to reach a stable entangled scaffold, is greatly favorable in compositions with 5 wt% of doped CP, reaching even a higher evaporation rate (4.50 ± 0.30 KMH). These results seem to be caused by a shrinkage effect named by the authors: “pudding effect.” The highly stable hydrogel double network demonstrated to have enough mechanical integrity for the hand manipulation of the gel in successive solar water evaporation cycles. Thus, the new system (with or without ALG) is a promising SAH candidate for self‐portable water desalinators for domestic uses. The hydrogel preparation can be performed in one‐pot reactor to customer up‐scale size necessities.

Exploring the Effects and Interactions of Conducting Polymers in the Volume Phase Transition of Thermosensitive Conducting Hydrogels

“…In the design of new thermosensitive conductive hydrogel materials, it is of crucial importance to understand the change in chemical interactions between the thermosensitive hydrogel and the supported conductive materials along the LCST point. , Thus, in this study, we synthesized a soft conductive polymer hydrogel by copolymerizing NIPAAm with MBA and loading it with PEDOT NPs, denoted as P­(NIPAAm- co -MBA)/PEDOT. This hydrogel was designed to exhibit excellent electrochemical properties.…”

“…30,31 The latter assumes critical importance in the context of TCH applications for water purification through solar evaporation, where understanding the relationship between bound/intermediate/ free water elucidates the reduction in evaporation enthalpy. 32,33 Nevertheless, despite the increasing importance of applications in response to the escalating issue of water scarcity, a knowledge gap exists regarding the chemical interactions between CPs and thermosensitive hydrogels. A deeper understanding of these interactions would enable more accurate fine-tuning of the properties of TCHs when utilized as solar-absorbing hydrogels (SAHs).…”

“…The role played by water molecules at the atomic level is of high significance. Employing Raman techniques and scrutinizing the intensity relationship of peaks corresponding to the O–H stretching of water molecules allows for the determination of the relationship between water bound to PNIPAAm (strong hydrogen bond) and interstitial water (intermediate strength hydrogen bond). , The latter assumes critical importance in the context of TCH applications for water purification through solar evaporation, where understanding the relationship between bound/intermediate/free water elucidates the reduction in evaporation enthalpy. , …”

Foaming photothermal inks for direct-ink writing: hierarchical design and enhanced solar-powered interfacial evaporation

“…40,41 In order to streamline complex manufacturing processes, there is a significant demand for the one-step synthesis of monolithic 3D interfacial SGs endowed with the capacity to govern hierarchically porous structures and to modulate the associated heat and mass transfer. 42–53 Considerable research efforts have been dedicated to crafting 3D material platforms that are durable, lightweight, scalable, capable of floating and resistant to overturning. 54–56 Despite the rapid and scalable fabrication of porous photothermal foams using diverse foaming techniques, the realization of a sophisticated and well-aligned microarchitecture with inherent anisotropic properties has remained elusive.…”