Hydrogels for the removal of the methylene blue dye from wastewater: a review

Water pollution is a major environmental issue with the rapid development of industry. Therefore, advanced technologies and materials are needed to remove pollutants from contaminated waters. The adsorption process displays many advantages such as high adaptability and removal efficiency for water sources of varying quality. Hydrogels have recently attracted attention due to their high adsorption capacity and structural stability, yet several issues remain to be explored, such as the number of reuse and engineering applications. Here, we review hydrogels for the removal of methylene blue from wastewater, with focus on hydrogel preparation and properties, adsorption performance and mechanisms, reusability and comparison with biological and chemical oxidation methods.