Abstract

Aims: In the present study, we investigate the photocatalytic properties of α-Ag₂WO₄ nanocrystals- modified Palygorskite (PAL) clay synthesized by the impregnation method. The PAL clay was chemically purified and heat-treated (500 ºC for 2 h), which served as an excellent supporting matrix for loading α-Ag₂WO₄ (α-AWO) nanocrystals.

Background: Water contamination is one of the most serious problems affecting human health, ecosystem survival, and the economic growth of societies. Industrial effluents, such as textile dyes, when not treated and improperly discharged into water resources are considered the main cause of water pollution. Thus the scientific community has been developing effective remediation technologies based on advanced oxidative processes to reduce the harmful effects of these organic pollutants.

Objective: This study aimed to improve the photocatalytic activity of PAL clay with α-AWO nanocrystals to degradation of Rhodamine B (RhB) dye.

Methods: We purified and heat-treated the PAL clay, synthesized nanocrystals of α-AWO nanocrystals and modified PAL clay with 30% α-AWO nanocrystals by the impregnation method. The modified PAL clay was able to improve RhB dye degradation. The materials were characterized by XRD, RAMAN, FE-SEM, FT-IR, XRF, etc. The samples were used as photocatalysts under UV-C lamps for the degradation of RhB dye in order to analyze their catalytic performances.

Results: The PAL clay modified with 30% α-AWO nanocrystals showed a catalytic efficiency of 79%, and degradation kinetics about 16 times higher when compared to PAL-500 only purified and heat-treated at 500 ºC. In this way, this PAL-modified is an alternative as a low-cost photocatalyst for the degradation of RhB dye.

Conclusion: Ultraviolet-visible spectra revealed that our materials have optical band gap energies controlled by indirect and direct electronic transitions and suitable to be activated under ultraviolet illumination. The adequate amount (30 wt.%) of α-Ag₂WO₄ nanocrystals added to PAL brought significant improvement in the photocatalytic activity for the degradation of rhodamine B. Finally, a photocatalytic mechanism was proposed in detail.

Keywords: Palygorskite, α-Ag₂WO₄ nanocrystals, optical band gap, photocatalysis, ultraviolet-visible, rhodamine B.

Graphical Abstract