Efficient degradation of selected polluting dyes using the tetrahydroxoargentate ion, Ag(OH)4−, in alkaline media

•We applied the reported tetrahydroxoargentate ion Ag(OH)4− for oxidation of surrogate organic recalcitrant dyes, by indirect redox oxidation.•Through UV-Vis and chromatography techniques, we showed the possibility to degrade recalcitrant compounds such as fluorescein and rhodamine.•Possible mechanisms of this indirect oxidation dye process using Ag(OH)4− are suggested.

The use of soluble and highly oxidizing Ag(III) in the form of the tetrahydroxoargentate ion Ag(OH)4− is reported for the oxidation of surrogate organic recalcitrant dyes (i.e., rhodamine 6G (Rh6G) and fluorescein (Fl)). The possible use of Ag(OH)4− for the treatment of these and other refractory compounds is assessed. Such dyes were selected due to their common occurrence, stability, refractory nature, the relatively high toxicity of Rh6G, and their structural similarity to Fl. Several reaction intermediates/products were identified. The results showed that the highly oxidizing tetrahydroxoargentate anion was capable of degrading these recalcitrant dyes. Furthermore, the final degradation products do not represent a higher environmental risk than the original surrogates themselves. In addition, the partial mineralization of the dyes was proven.