Catalytic materials applied for dye removal in advanced oxidation processes: a mini review of studies from 2015 to 2025

This review explores how advanced oxidation processes (AOPs) and photocatalytic methods are used to break down toxic dyes in wastewater, which are difficult to remove using traditional treatment methods. The motivation for this research stems from the severe environmental impact of dye-contaminated wastewater, which harms aquatic life, disrupts ecosystems and poses significant health risks to humans. Effective treatment methods are urgently needed to ensure environmental sustainability and protect public health. The novelty of this review lies in its comprehensive synthesis of the latest research over a focused ten-year period (2015-2025). It systematically compares the performance of various processes and highlights the importance of total organic carbon (TOC) removal percentage as the definitive measure of a method’s effectiveness, moving beyond simple colour removal. The reviewed literature itself demonstrates significant novelty, featuring the development of new catalytic materials like ZnO@SnOx@nZVI and S-doped TiO2 nanoparticles, as well as the investigation of specific mechanisms, such as sulphate radical formation. The findings show a clear trend toward highly efficient photochemical, AOP, combined/hybrid, chemical, and electrochemical processes, which consistently achieved a wide range of degradation rates from 77 to 100%. The methods operate effectively with dye concentrations spanning from 10 mg/L to more than 200 mg/L which demonstrates their suitability for industrial use. Most research studies use synthetic wastewater instead of actual industrial wastewater that contains multiple interfering compounds which creates a major practical application challenge.