The "Pudding Effect" to Promote Solar-Driving Water Purification

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. A solar absorber hydrogel (SAH) is designed to favor the water desalination with sunlight irradiation. The inter- and intramolecular forces created within the PNIPAAm hydrogel by adding charges from ionic polymers (PEDOT:PSS) and hydrophilic alginate polysaccharide (biopolymer) play an important role for the water steam generation.image