Functional Hydrogels—Enabling the Gateway for Sustainable Water Treatment and Harvesting Technologies

In recent years, the combination of industrial growth and population expansion has intensified the global freshwater shortage, leading to extensive research into advanced water treatment and harvesting methods. Functional porous materials such as hydrogels and aerogels comprising polymer materials alone or with the addition of biomass, nanoparticles, and carbon-based materials having a 3D network structure, have gained significant attention in this field due to their superior water absorption, separation capability, and their ability to harvest water. This review examines techniques for hydrogel synthesis, including chemical and physical cross-linking. It highlights absorption/desorption of water, different water states in hydrogels, and the factors affecting these processes. Importantly, this review thoroughly covers the current developments in the application of hydrogels for water treatment techniques such as removal of organic pollutants, pharmaceuticals, and heavy metal removal, water disinfection, oil/water separation, and reverse osmosis. An assessment of existing shortcomings and potential future developments for hydrogel-based water treatment and purification systems rounds out the review.