Stabilizing Semi-Interpenetrated Alginate/Pedot Hydrogels via Glyoxal-Mediated Covalent Crosslinks for Water Steam Generation

The chemical and physical stability of bio-hydrogels are of utmost interest to avoid the premature degradation of the polymer and to favor cyclic material operations (i.e., material recovery and re-using). In this work, the stability of different alginate hydrogels semi-interpenetrated with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conducting polymer (Alg/PEDOT), which acts as a photothermal absorber is examined. More specifically, the behavior of Alg/PEDOT hydrogels ionically and covalently crosslinked with Ca²⁺ ions and glyoxal, respectively, has been compared when used as water purification platforms. The homogenous porosity and higher cycling capacity of the glyoxal-crosslinked gels provide superior performance for water-steam generation under sunlight irradiation than that of the ionically stabilized gel. Furthermore, increasing the glyoxal cross-linking reaction time prove to have little effect on the porosity and the efficiency of freshwater supply from an artificial seawater solution. Covalent cross-links provide thermal absorber (PEDOT:PSS) retention capacity in artificial seawater, which is critical to maintaining such efficiency with the increasing number of purification cycles. This research opens new frontiers to promote the use of alginate biopolymer in chemical engineering processes such as water desalination, directly addressing the United Nations Sustainable Development Goals for Clean Water & Life on Land.