A critical review on three-dimensional cellulose-based aerogels: synthesis, physico-chemical characterizations and applications as adsorbents for heavy metals removal from water

Pollution and contamination of water with heavy metals is a global challenge which demands efficient, economic and sustainable solution. The grafting/addition of poly-functional groups (ligands) on the polysaccharides chains can high adsorption affinities towards heavy metals. Aerogels are a class of three-dimensional porous materials with outstanding physic-chemical characteristics (low density, high surface to volume ratio and controllable surface chemistry). In the recent years, aerogels have gained sufficient attention for the remediation of heavy metal ions from wastewater. The present review critically analyses the various synthesis routes for the cellulose aerogels and their applications as an adsorbent for heavy metal ions from water. This review critically analyzes the various synthesis routes for three-dimensional cellulose-based aerogels, their physico-chemical characterizations and removal mechanisms for the adsorption of heavy metal ions from water with insights into isotherm and kinetic models. Challenges (reactor configuration, scale-up, and proper selection of drying technique) and future research directions for the development of robust and efficient cellulose aerogels for the mitigation of heavy metal ions from water have also been elucidated.