Responsive starch-alginate-containing triazine-based porous organic polymer beads towards hexavalent chromium

Some heavy metals (e.g., Cr(VI)), also known as potentially toxic metals, concern the population's health in water due to their persistence, bioaccumulation, and high toxicity. Highly porous materials based on biodegradable and low toxic polysaccharides combined with advanced tailor-made polymers with high surface area and permanent porosity (i.e., porous organic polymers - POPs) are promising technologies for metal sensing, removal, and recovery. In this study, novel starch-alginate-based gel beads containing an imine-linked triazine-based porous organic polymer (IT-POP) were developed, and both the IT-POP and the best beads formulation were applied for sorption and sensing of Cr(VI). Kinetic studies suggested a chemisorption mechanism, explained by electrostatic attractions, and proved the negligible contribution of Cr(VI) to Cr(III) reduction. Thermodynamically, sorption processes were spontaneous and endothermic, leading to increased entropy. The materials also acted as fluorescence chemosensors, undergoing a linear Stern-Volmer fluorescence quenching in the presence of the metal oxyanions. Overall, the results proved that the anchoring of the advanced functional material did not affect its high sorption performance, meaning that composite starch-alginate beads may be an efficient, more economical, and processable alternative for the Cr(VI) remediation.