Research Progress of Cellulose-Based Double-Network Hydrogel in Water Pollution Control: Preparation, Regulation, Applications

Heavy-metal ions, organic dyes, antibiotics, and microplastics (including nanoplastics), which can bioaccumulate and are potentially toxic, pose serious threats to aquatic ecosystems and human health. Traditional adsorbents face limitations in complex wastewater, as they often exhibit poor selectivity, low mechanical strength, and poor reusability. Cellulose-based double-network (DN) hydrogels, which address these limitations by integrating two functionally complementary networks, consist of a rigid cellulose-based first network that maintains structural integrity and provides a biodegradable skeleton, and a flexible second network that enhances toughness, swelling, mass transfer, and functional-group accessibility. This review summarizes recent progress in cellulose-based DN hydrogels, covering preparation strategies, network composition, and pollutant adsorption applications. Heavy-metal ions are captured mainly through coordination complexation and ion exchange. Organic dyes and antibiotics are removed through electrostatic interactions, hydrogen bonding, and π–π interactions. Microplastics are adsorbed mainly through physical interception and electrostatic interactions. The recyclability of these hydrogels is evaluated in terms of regeneration efficiency, capacity retention, and structural stability. Finally, future research trends are outlined, including new green preparation strategies, evaluation in real wastewater systems, and large-scale production and application.