Critical review of magnetic polysaccharide-based adsorbents for water treatment: Synthesis, application and regeneration

Magnetic polysaccharide-based adsorbents have attracted more and more attention as novel adsorbents for remediating polluted water due to their biocompatibility, high performance, low cost, easy separation and renewability. In this review, magnetic adsorbents based on polysaccharides for aqueous processing have been thoroughly studied, reviewed and discussed. The synthesis and modification methods as well as their applications to remove various contaminants from water are highlighted, especially the removal of mixed pollutants, and the relationships between adsorbent functional groups, pollutant characteristics and adsorption mechanisms. The possible regeneration, environmental impacts and cost-effectiveness of these adsorbents have been investigated as well. It was found that the modified magnetic polysaccharide-based adsorbents have excellent stability, surface morphology and adsorption performance. Mixed pollutants can be more effectively removed via adsorbents prepared by combining diversiform functionalization and modification approaches. Inorganic pollutants are removed by electrostatic interaction, complexation, chelation or ion exchange, whereas organic pollutants are mainly adsorbed through electrostatic interaction, hydrogen bonding, pi-pi interaction and ion exchange. Based on the biodegradability and high temperature sensitivity of polysaccharides, it is the most economical, effective and convenient approach to regenerate magnetic polysaccharide-based adsorbents by chemical method (eluted with suitable desorbents). Considering the full life cycle costs, magnetic polysaccharide-based adsorbents with high raw material costs are identified to be economical compared with traditional adsorbents due to their high performance, high recovery rate and excellent reproducibility. Their regeneration and reuse performance may also compensate for adverse environmental impacts. There are still some critical challenges in the further research of magnetic polysaccharide-based adsorbents, such as their mass synthesis and large-scale application, desorption kinetics and desorption mechanisms, process economy and fate in the environment.