Aerogel-based adsorbents as emerging materials for the removal of heavy metals from water: Progress, challenges, and prospects

The removal of heavy metals from aqueous environment is essential to safeguard the environment, human health, and aquatic life. Aerogels, highly porous three-dimensional materials, have gained considerable attention in recent years as emerging materials in water treatment. The adjustable surface chemistry, low density, high specific surface area, and loose porous structure are some of the key features that make them the ideal candidates as adsorbents. This review critically evaluates the recent developments in the applications of aerogel-based adsorbents for the confiscation of potentially toxic heavy metal ions from water and wastewater. Various routes for the synthesis of aerogel-based adsorbents and their physicochemical characteristics are discussed. The effects of key influencing parameters such as solution pH, temperature, adsorbent dosage, coexisting ions, initial concentration of heavy metals, and contact time are critically evaluated. The interaction mechanisms of metal ions with aerogel-based adsorbents and regeneration capabilities of spent materials are described in detail. Furthermore, the potential of the aerogel-based adsorbents in real wastewater treatment is also evaluated. Based on the reported studies, various gaps are identified and recommendations for future research are made. Assessing the potential of these adsorbents in real water treatment and the development of facile and green synthesis routes for the formation of aerogel-based materials on a larger scale are key challenges that need immediate attention. Furthermore, the development of novel strategies for regeneration after adsorption and evaluating the potentially toxic and environmental impacts of aerogel-based materials are other research gaps that need to be filled. Despite various challenges, the research progress in the field suggests that aerogel-based materials might play a critical role in water purification in future.