Herbicides are hazardous organic pollutants that contribute to the risk of environmental contamination. The aim of this work was to investigate the synergistic effect of silver (Ag) and gold (Au) bimetallic nanoparticles deposited on palygorskite (PAL) in the presence of TiO₂ for photodegradation of bentazone (BTZ) herbicide under UV light. Ag and Au@Ag nanoparticles exhibited an average size below 75 nm and surface charge values less than − 30 mV. UV-Vis spectroscopy indicates the formation of core@shell bimetallic nanoparticles. XRD results showed the interactions between the NPs and the palygorskite structure. SEM images clearly illustrate the presence of small spherical particles distributed in the clay fibers. The control of the size and distribution of the nanoparticles played an important role in the properties of the composites. The degradation of the herbicide BTZ showed that nanoparticles, clay, and only TiO₂ did not produce satisfactory results; however, when Ag-Pal and Au@Ag-Pal were in the presence of the TiO₂, the degradation was efficient. The best photodegradative system was Au@Ag-Pal+TiO₂, which was maintained after the third cycle. The bentazone photodegradation using Au@Ag-PAL+TiO₂ exhibited toxicity against Artemia salina. Therefore, Au@Ag-PAL+TiO₂ photocatalyst showed that the synergy of bimetallic nanoparticles deposited on clay for enhanced photodegradation activity of bentazone herbicide.