Photoelectrocatalytic degradation of anthraquinone dyes: Catalytic materials, reaction pathways, and post-treatment toxicity

Anthraquinone dyes are structurally persistent colorants used in textile and related industries, and their incomplete treatment can result in transformation products that remain in the aqueous phase. Moreover, their presence in water bodies reduces light penetration, affecting photosynthesis and other essential biological processes in aquatic ecosystems and posing risks to human health. This critical review evaluates photoelectrocatalytic treatment of anthraquinone dyes, using related photocatalytic and electrochemical studies to examine catalytic materials, reaction pathways, analytical endpoints, and post-treatment biological effects. A structured literature search prioritized studies published from 2017 to 2026, while earlier papers were retained when they provided mechanistic or comparative evidence. Among the treatment studies compiled for endpoint analysis, 45% relied primarily on decolorization or nonspecific structural evidence, 20% identified transformation products without direct evidence of organic‑carbon removal, and 35% reported total organic carbon or chemical oxygen demand measurements. Only 15% included a post-treatment biological assay. The literature still relies heavily on decolorization data, while mineralization, intermediate identification, catalyst stability, energy consumption, and post-treatment ecotoxicity remain insufficiently addressed. Heterostructures, conductive modifiers, and externally applied bias can improve charge extraction and apparent dye removal, but comparisons remain limited by inconsistent irradiation conditions, electrical inputs, reactor dimensions, and analytical endpoints. Rather than evaluating photoelectrocatalysis performance solely by dye decolorization, this review links catalyst design to degradation pathways, evidence of mineralization, and ecotoxicological outcomes, providing a more realistic basis for assessing the environmental safety and technical viability of photoelectrocatalysis-based treatment of effluents containing anthraquinone dyes.