Hydrogel-polyurethane interpenetrating network material as an advanced draw agent for forward osmosis process

• A hydrogel-polyurethane interpenetrating network (HPIPN) was prepared.
• A high water flux (17.9 LMH) was achieved using HPIPN as draw agent.
• 3-D continuous network can enhance the water transport inside the hydrogel monolith.
• Water in hydrogel can be effectively recovered under simulated sunlight.

Water desalination and purification are critical to address the global issue of the shortage of clean water. Forward osmosis (FO) desalination is an emerging low-cost technology for clean water production from saline water. The lack of a suitable draw agent is one of hurdle for the commercialization of FO desalination technology. Recently, the thermoresponsive hydrogel has been demonstrated to be a potential draw agent for the FO process. However, the commonly used hydrogel powder shows a much lower flux than other kind of draw agent such as inorganic salts. In this work, a hydrogel-polyurethane interpenetrating network (HPIPN) with monolith form was prepared by controlling the radical polymerization of the monomers (N-isopropylacrylamide and sodium acrylate) in the macropores (∼400 μm) of commercial polyurethane foam (PUF). These HPIPN composites show a flux as high as 17.9 LMH, which is nearly 8 times than that of hydrogel powders (2.2 LMH). The high flux is attributed to the 3-D continuous hydrogel-polyurethane interpenetrating network, which can effectively enhance the water transport inside the monolith.

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