Role of Adsorptive Concentration in Fenton-Like Degradation of Organic Pollutants by Biopolymeric FeOOH/Graphene Oxide Composite Catalyst: Proof of Concept

Despite advances in adsorption chemistry to mitigate water contaminants, the intact nature of contaminants after adsorption limits the technique's wide application. Here, a nanostructured material is engineered and a conceptual study developed—adsorption-coupled Fenton-like reaction (ACFLR)—and it is shown that adsorptive concentration of a pollutant on an adsorbent favors Fenton-like degradation. Sodium alginate (SAG) is introduced as a soft-gelling template for in situ generation of FeOOH, which stabilizes graphene oxide (GO) nanosheets (SAG-FeOOH/GO) to yield active Fenton-like catalytic adsorptive sites. The catalyst architecture—the biopolymer-functionalized FeOOH-supporting GO nanosheets—are responsible for the ACFLR. Methylene blue (MB) is concentrated on SAG-FeOOH/GO via electrostatic and pi–pi interactions and these interactions are responsible for the adsorptive removal of MB. After adsorptive concentration of MB on the surface of SAG-FeOOH/GO, the proximity of Fenton-like catalytic sites enhances the efficient use of the short-lived reactive oxygen species compared to that of the MB in bulk solution (nonadsorbed MB) for efficient Fenton-like reactions. The role of adsorption during the Fenton-like reaction is proved by the structural degradation of MB by the concentrated MB on SAG-FeOOH/GO under Fenton-like conditions followed by desorption, which gives the concentration of degraded MB after the step-wise action of adsorption and Fenton-like degradation.