Heavy Metal Ions in Wastewater Affect the Photodegradation of Phenol‐4‐sulfonic Acid over Biphasic TiO 2 /Activated Carbon Fiber Composites

The effect mechanism of Cu 2+ , Zn 2+ and Ni 2+ ions in wastewater on photocatalytic activity remained unknown. For phenol‐4‐sulfonic acid (PSA) photodegradation, we fabricated anatase/rutile/activated carbon fiber composites (A/R/ACFs) by the hydrothermal deposition of rutile TiO 2 nanorods and anatase TiO 2 nanoparticles on ACFs. A/R/ACFs exhibited better photocatalytic activity than both R/ACFs and A/ACFs because anatase/rutile heterojunctions supported electron transfer from rutile to anatase. All Cu 2+ , Zn 2+ and Ni 2+ ions in wastewater improved the chemical stability of PSA by forming PSA‐Cu(II), PSA‐Zn(II) and PSA‐Ni(II) complex compounds, and thus inhibited the PSA photodegradation. Notably, the as‐formed photoelectrons over A/R/ACFs were partly consumed due to the reduce reaction of Cu 2+ ions into Cu + /Cu 0 , avoiding electron‐hole recombination and improving PSA photodegradation efficiency. No reduce reaction of Zn 2+ and Ni 2+ ions occurred during the PSA photodegradation process. Hence, the A/R/ACFs are an effective photocatalyst for wastewater purification, and low Cu 2+ concentrations facilitated the PSA photodegradation.