Self-sufficient Fenton-like degradation by Cu-TA encapsulated melamine sponge

Abstract

Water contamination is a severe and urgent issue, and advanced oxidation processes (AOPs) offer promising solutions for water purification. Among these, copper-based Fenton-like reaction demonstrate advantages such as rapid reaction kinetics and low reduction potential. However, a major limitation of most Fenton-like reactions is their reliance on externally added H₂O₂, which poses risks in transportation, storage, and management. To address this, developing self-sufficient Fenton-like systems with in-situ H₂O₂ generation is critical. In this study, we conjugated copper ions (Cu²⁺) and tannic acid (TA) on a melamine sponge (MS) substrate to fabricate a self-sufficient Fenton-like catalyst (MS-Cu-TA). MS exhibits high porosity and absorbency, which facilitate efficient liquid absorption for the degradation process. The H₂O₂ content generated by a single MS-Cu-TA sponge was determined as ∼0.19 mmol, which was sufficient to sustain the Fenton-like reaction. Methylene Blue (MB) degradation results showed that MS-Cu-TA achieved comparable degradation efficiency (∼60% within 0.5 h) without exogenous H₂O₂. Notably, in this specific dye degradation process, adsorption and degradation occurred simultaneously. Results from reactive oxygen species (ROS) quenching tests and electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the dominant ROS generated is hydroxyl radicals (•OH), which originates from in-situ formed H₂O₂. The in-situ H₂O₂ generation is likely attributed to the auto-oxidation of TA, which acts as both reducing agent and H₂O₂ precursor. Concurrently, TA reduces Cu²⁺ to Cu⁺, which catalyzes H₂O₂ to generate •OH via a Fenton-like reaction. This work provides valuable insights for developing self-sufficient Fenton-like systems in wastewater treatment.