Novel immobilized polyoxometalate heterogeneous catalyst for the efficient and durable removal of tetracycline in a Fenton-like system

Polyoxometalates (e.g., phosphotungstic acid) provide a new viewpoint for the development of efficient heterogeneous Fenton-like catalysts due to their distinct chemical structure and catalytic properties. In this work, a polymer composite (PWA/PAN) was successfully prepared by doping phosphotungstic acid (PWA) as an active component in the polyaniline (PAN) matrix. The prepared composite was then applied to degrade tetracycline (TC) in a Fenton-like system. Characterization results confirmed that PWA was dispersed in the inorganic carrier with its unique and stable Keggin-type structure, and the inherent chain structure of PAN did not change markedly. Compared with common heterogeneous Fenton-like catalysts, PWA/PAN displayed better catalytic activity for H2O2 decomposition and TC removal. In the pH range of natural water (pH 6–11), PWA/PAN efficiently catalyzed H2O2 decomposition. Under optimal conditions (20 °C, pH0 7, catalyst dose of 0.5 g/L, and H2O2 concentration of 50 mM), the degradation efficiency of TC and the decomposition efficiency of H2O2 reached 100% and 0.1010 min−1 within 30 min, respectively. PWA/PAN exhibited excellent catalytic activity durability and structural stability. TC degradation efficiency by the PWA/PAN/H2O2 system did not distinctly decrease. In addition, the degradation mechanism of TC in the PWA/PAN/H2O2 system was revealed. Results disclosed that •OH was the main contributor to the degradation of TC, and it achieved most of mineralization of TC. This work is expected to tackle the common issues of easy deactivation, poor stability, and low H2O2 decomposition efficiency of Fenton-like catalysts at neutral pH and provide novel materials for the treatment of antibiotic pollution.