Hybrid photosensitizer based on halloysite nanotubes for phenol-based pesticide photodegradation

Abstract

Abstract The paper describes the studies on the photodecomposition of 4-n-nonylphenol (NP), a widely used pesticide and endocrine disrupting agent. For this purpose a new hybrid photosensitizer (RB-HNT) was obtained composed of Rose Bengal (RB) incorporated into the halloysite nanotubes (HNT). The photosensitizer was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal microscopy, as well as UV–Vis and fluorescence spectroscopies. The results confirmed that the crystalline structure of HNTs was preserved after modification with RB. The obtained hybrid material efficiently adsorbs hydrophobic compounds. It was also found to be an efficient photosensitizer for singlet oxygen generation. RB-HNT combines the advantages of both of its components, i.e., the ability to adsorb hydrophobic pollutants, which is characteristic for HNT, and photocatalytic properties of RB. Photooxidation kinetics of n-nonylphenol in the presence of RB-HNT and in the aqueous solution of RB were followed spectrophotometrically and compared. The photooxidation in the presence of Bengal Rose followed the first order kinetics, while in the presence of sensitizer (RB-HNT) observed zero-order kinetics. Furthermore the pesticide oxidation by the hybrid catalyst was found to be more efficient. The products formed after various irradiation times were identified by the GCMS analysis and the photodegradation pathway has been proposed.