Innovative spherical hydrogel architecture for efficient solar-driven desalination: A waste-to-resource approach

This study presents an innovative spherical hydrogel architecture designed for efficient solar-driven interfacial evaporation, leveraging a waste-to-resource approach by recycling sodium polyacrylate (PAAS) from discarded diapers. The developed PAAS/polyvinyl alcohol (PVA) composite hydrogel (PPSH) integrates recycled PAAS with PVA and Chinese ink to form a hierarchical porous structure that enhances water transport and photothermal conversion efficiency. The spherical design of PPSH significantly increases the steam dissipation area, reduces heat loss, and improves salt resistance, achieving an evaporation rate of 3.18 kg/(m 2 ·h) under one sun illumination. The hydrogel demonstrates exceptional desalination performance, reducing total dissolved solids (TDS) by 2–4 orders of magnitude in seawater with varying salinities (up to 250 ‰) and maintaining stable operation over extended periods. Additionally, PPSH exhibits high versatility in treating domestic wastewater across a broad pH range (2–13), meeting the World Health Organization (WHO) drinking water standards. Outdoor field tests further validate the practical applicability of PPSH, with a daily water production rate of 22.87 kg/m 2 under natural sunlight. This work not only addresses freshwater scarcity through sustainable waste utilization but also provides critical insights into the structural design of scalable solar desalination technologies, offering a promising solution for decentralized water purification.