Facile Synthesis of Hybrid-Polyoxometalates Nanocomposite for Degradation of Cationic and Anionic Dyes in Water Treatment

Abstract

Photocatalysis emerges as a promising method for treating organic dye contaminated wastewater. This process involves the use of photocatalysts through light activation, typically semiconductors such as titanium dioxide (TiO2) or polyoxometalates (POM) to generate reactive species capable of degrading organic pollutants. Several factors influence the photodegradation of ionic and cationic dyes including chemical properties, reaction mechanism and degradation efficiency. This work evaluated photodegradation performance of methyl orange (MO) and malachite green (MG) dyes using hybrid-polyoxometalate (HPOM) photocatalyst. Fourier Transform Infrared Spectroscopy (FTIR) identified the characteristic band at 3463.66 cm–1 (O-H) and 997.74 cm–1 (W-O). Scanning Electron Microscopy (SEM) revealed the presence of rod-like and granular structures in HPOM, representing silver acetate and sodium tungstate. X-ray diffraction (XRD) confirmed characteristic peak of Keggin structure, revealing high crystallinity of HPOM. UV-assisted photodegradation was evaluated on different parameters (initial dye concentration, photocatalyst dosage and pH), highlighting HPOM’s better affinity for degrading cationic dye. The optimum photodegradation conditions for MG and MO dyes were 20 ppm dye concentration, 100 mg photocatalyst dosage, and pH 7 and 8, respectively. The kinetic data was fitted with the Langmuir Hinshelwood kinetic model, indicating pseudo-first-order kinetics. HPOM exhibited a higher rate constant, k for MG (k = 0.0068 min–1) than MO (k = 0.0029 min–1).