Sustainable Technologies for Adsorptive Removal of Estrogens from Water: A Comprehensive Review for Current Advances

Environmental pollution and eco-toxicological effects caused by estrogens have attracted global concerns due to their strong estrogenic potencies. Adsorption is one of the most efficient technologies for estrogen removal owing to its simple operation and techno-economic feasibility. However, to the best of our knowledge, there are few reviews specifically concentrating on a comprehensive assessment of the latest progress about estrogen adsorptive removal. Therefore, the advances of adsorbents regarding estrogen removal including commercial activated carbons, biochars, carbon nanotubes, graphenes, polymers, molecular imprinting polymers, mesoporous silicas and their modified materials were presented detailedly in this work. Adsorption performance was dependent on adsorbents' structure characteristics. Modification was capable of improving adsorption capacities by increasing adsorption sites. The commonly best-fitted models for isotherms and kinetics were Langmuir/Freundlich model and pseudo-second-order kinetic model, respectively. Hydrophobic interaction, π-π interaction, hydrogen bonding, host-guest interaction, specific binding, electrostatic interaction or their combined effects generally contributed to adsorption mechanisms. The influences of water matrices, including pH, co-existing ions, organic matters, colloids, inorganic nanoparticles, microplastics and sediments, on estrogen removal were investigated in detail. Both solvent and degradation methods were employed for estrogen adsorbents regeneration. Furthermore, the improvement and challenge of estrogen adsorption were proposed to promote the further research. This work not only attempts to converge the scattered knowledge associated with estrogen adsorption, but also provides a deep and comprehensive understanding of estrogen adsorption behavior, which is beneficial to construct the basis for the further research on high-performance adsorbents for selective estrogen removal with designed functionality.