Kaolinite−Based Photocatalysts for Azo Dyes Degradation under Xenon and Sunlight Irradiations: The Effects of Electro-Deionization and Impregnation Methods

Azo dyes pose a significant environmental concern due to their high stability and resistance to natural degradation. Therefore, this study aims to explore the use of kaolinite−based photocatalysts for azo dye degradation with methylene blue (MB) as an azo dye model. The transition metals−kaolinite composites (TMs-kaolinite) (where TM = Fe, Ni, or Zn) were prepared using 2 methods, namely electro-deionization (ED) and impregnation (IMP). The performance of TMs-kaolinite photocatalysts for azo dye degradation was evaluated using xenon and sunlight irradiations. The activities of degradation reaction of MB were observed by varying photocatalyst types, time of illumination, and type of irradiation. The most excellent photocatalytic activity for degradation of MB was Zn-Kaolinite IMP with an efficiency of 92% during 90 minutes of irradiation. Meanwhile, pristine kaolinite was the best adsorbent for the removal of MB without degradation process, with an adsorption efficiency of 98%. These results showed that TMs-kaolinite showed high photocatalytic activity for degradation of azo dye, with sunlight irradiation being more effective than xenon irradiation. Different forms of TMs-kaolinite catalysts had different phenomena and mechanisms for the photodegradation of MB. TMs in TMs-kaolinite played an important role in the performance of photocatalysts