Degradation of azo dye (direct red 89) using H2O2/periodate process-parameter optimization and mixture composition evaluation.

As a fast and efficient process, a periodate (PI)-based advanced oxidation process was used to degrade direct red 89 (DR89), wherein hydrogen peroxide (H₂O₂) was employed to activate PI (H₂O₂/PI process) to investigate the effect of operating parameters and mixture composition. The PI was efficiently activated by H₂O₂ to degrade 67% of DR89 within 1 min. Acidic pH was more favorable to high-efficiency degradation than the basic pH; at pH 3 degradation rate was 94.31%, while it was only 20.92% at pH 11. The degradation rates were further enhanced with increasing H₂O₂ and PI dose up to certain optimum values, later it decreased which was dependent upon the amount of hydroxyl (^●OH) and iodyl (IO₃^●) radicals produced. The quenching experiments suggested that IO₃^●, ^●OH, ¹O_2, and O₂^●- are the predominant reactive species during H₂O₂/PI process, while O₂^●- radicals are the primary precursor of other reactive oxygen species. The results of this study suggested that H₂O₂/PI is the efficient and rapid treatment method to degrade persistent organic pollutants (POPs) from polluted wastewater sources.