Thermoresponsive and antifouling hydrogels as a radiative energy driven water harvesting system

Abstract

Hygroscopic and temperature-responsive hydrogels with the potential to harvest water from air followed by its release in liquid or vapor form have seen much interest as water harvesting materials for arid regions. However, the purification of water from wastewater remains a major challenge and only a handful of technologies are being investigated for their potential to purify water from polluted resources. In this study, we explore the synthesis of antifouling and radiative heat driven water-harvesting hydrogels that are capable of absorbing clean water from resources polluted with organic waste, followed by its release, mainly in liquid form, as a function of temperature. The new thermoresponsive hydrogels are comprised of hygroscopic and antifouling vitamin B5 analogous monomers (B5AMA) and 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) and are evaluated for their kinetics of water uptake and release capacity. The poly(B5AMA-co-MEO₂MA) hydrogels are further evaluated for their ability to recycle clean water from organic polluted wastewater resources and for their potential to develop a radiative energy driven water harvesting system. The hydrogels synthesized are found to be extremely hygroscopic and can recycle 6.84 g of water per g of hydrogel (∼85% water recycling efficiency) upon heating at 60 °C. The hydrogels are also extremely antifouling and can repel 1.5 × 10⁹ bacterial cells per mL of wastewater. The water release rate of the hydrogels is dependent upon the time and temperature and can be tuned to develop a solar fueled water harvesting system.