Fenton-like reaction of glucose oxidase-glucose@Kaolin coupled with green rust: A framework triggering FeⅣ=O in refractory pollutants degradation

Abstract

Fenton reaction has been widely applied with fast reaction speed and strong oxidation capacity, but it also has some noticeable defects of acid-alkali reagents over-consumption and strong tendency of H2O2 self-decomposition under high concentration. In order to overcome these shortcomings, this study proposed a green rust/Kaolin fixed glucose oxidase (GR/Glu-Kaolin@GOD) Fenton system. The production of H2O2 from Glu-GOD@Kaolin system was catalyzed by GR to generate oxidizing species and degrade aniline organic wastewater. Results showed that the enzymatic reaction could produce H2O2 at a gradual incremental pace in situ, avoiding active agent quenching and heightening its utilization rate. Furthermore, this system was proved to have an excellent removal effect under neutral and weak-acid conditions, which was superior to the traditional homogeneous Fenton with a narrow pH range. In this study, diversified active substances in the system were detected including hydroxyl radicals, FeIV=O and superoxide radicals, whose real-time degradation contribution changes were calculated and analyzed. On basis of the results, the roles of these active agents and the interactional principles among them were explored. Furthermore, the close correlation between Fe2+ in GR and GlcA and degradation mechanisms upon 3, 4-DMA were set forth in detail. Especially, in the middle and later stage of the reaction, the contribution of FeIV=O, generated through the complexes between Fe(Ⅱ) and GlcA, would continue to increase due to the gradually benign pH environment and FeIV=O gave full play to advantages in decarboxylating those intermediate products containing methyl, etc, which consequently enhanced both the oxidation efficiency and effluent biodegradability. In addition, the optimal operational conditions were determined through response surface data analysis. Moreover, the residual Glu and small molecular acids in the water could be fully exploited as suitable microbial carbon sources, and elevate the efficiency of the subsequent biological treatment.