12-Tungstophosphoric acid/BEA zeolite composites - Characterization and application for pesticide removal

Tungstophosphoric acid and BEA zeolite composites were synthesized by wetness impregnation, followed by ultrasonication and calcination. Composites were characterized using Raman spectroscopy, thermal analysis and pH-dependent zeta potential. Spectroscopic measurements indicated the interaction of acid and the support by binding of polyanion terminal oxygens and BEA extra framework H+ via hydrogen bonds. Evaluation of prepared composites revealed their higher efficiency in nicosulfuron adsorption, in comparison to parent zeolite. All prepared composites showed excellent adsorption properties for pesticide removal in the range 12.1-25.8 mg of nicosulfuron per gram of investigated sample. Better adsorption capacity was found for sonicated samples in comparison to as-synthesized and calcined ones. It was found that the amount of polyanion in the composites and the extent of the particles surface charge are not crucial for the adsorption application, it is rather the uniformity of the zeolite surface coverage with the polyanion that is was more important.