Praseodymium-doped cadmium tungstate (CdWO₄) nanoparticles for dye degradation with sonocatalytic process

In the present work, praseodymium-doped cadmium tungstate (Pr-CdWO4) nanoparticles were synthesized, characterized and used as catalysts in a sonocatalytic process to degrade the toxic synthetic azo dye Remazol Black B (RBB). RBB was degraded by 93.9% operating at optimal conditions (pH = 3, C = 100 mg/L, catalyst dosage = 0.35 g/L, T = 298 K and irradiation time100 min) under an ultrasonic bath at 60 kHz. Further, the addition of different radical scavengers and enhancers to the reaction was assessed. It was found that the addition of the radical scavengers sodium sulfate, sodium carbonate, and sodium chloride decreased RBB degradation from 93.9% to 86.0%, 78.0%, and 71.2%, respectively. On the contrary, the addition of the enhancers potassium periodate, peroxydisulfate and hydrogen peroxide slightly increased the RBB degradation from 93.9% to 95.3%, 96.1%, and 98.7%, respectively. The sonocatalytic process resulted in higher RBB degradation than by applying separately sonolysis (34.7%) and the catalyst as an adsorbent (39.5%). The experimental data followed both the pseudo-first-order (PFO) and Langmuir-Hinshelwood (L-H) kinetics models. However, the PFO gave better fitting (R² = 0.993) than the L-H kinetic model (R² = 0.9025) at the same optimum experimental conditions. The obtained results pointed out the sonocatalytic process with Pr-doped CdWO₄ nanoparticles as a promising process for the degradation of azo dyes and other hazardous organic compounds existing in wastewater.