Harnessing metallurgical slags for water treatment: Advances in organic pollutant degradation with and without hydrogen generation, and in heavy metal removal

The removal of recalcitrant organic pollutants and heavy metals from water remains a critical challenge for safe drinking water supply and wastewater reuse. Although advanced oxidation processes (AOPs) and adsorption‐based technologies have proven effective, the identification of efficient, low‐cost, and sustainable materials limits their large‐scale deployment. This review systematically examines metallurgical slags (MS)—industrial by‐products enriched with reactive phases such as FeO, Fe 3 O 4 , CuFe 2 O 4 , and CaO—as multifunctional platforms integrating photocatalysis, adsorption, Fenton‐like oxidation, and sulphate radical activation for advanced water treatment. The analysis reveals that the multicomponent mineral matrix of MS‐based materials enables broader visible‐light absorption and enhances charge separation compared to conventional pure semiconductors, while simultaneously providing a high removal capacity of heavy metals and metalloids. Copper smelting slags after thermal treatment emerge as particularly promising due to their p‐n heterojunction character and dual capacity for hydrogen co‐generation and contaminant degradation. Key factors governing performance—including slag composition, particle size, pH, and sacrificial agent selection—are critically discussed. Overall, this work positions MS‐based materials as viable circular economy alternatives to conventional photocatalysts and adsorbents, and identifies the main research gaps that must be addressed before industrial‐scale implementation.