Simultaneous arsenic and fluoride removal using {201}TiO2–ZrO2: Fabrication, characterization, and mechanism

Highlights: • {201}TiO₂- ZrO₂ composite is fabricated with anatase TiO₂ and monoclinic ZrO₂. • The composite simultaneously removes co-existing As and F in real groundwater. • Ti sites are occupied by As(III/V) forming bidentate binuclear surface complex. • Zr sites preferentially adsorb F/As(III) in monodentate mononuclear structures. -- Abstract: The coexistence of arsenic (As) and fluoride (F) in drinking water is an urgent environmental issue that causes increasing public concerns. The need for effective simultaneous removal of As and F has motived great research efforts. Herein, a novel {201}TiO₂–ZrO₂ composite was synthesized and its application mechanism was explored. Batch adsorption experiments show that the As(III), As(V), and F adsorption followed the pseudo-second-order kinetics with the Langmuir adsorption capacity at 58.5, 21.6, and 13.1 mg/g, respectively. EXAFS and in situ ATR-FTIR results suggested that TiO₂ surface sites were occupied by As(III) and As(V) in bidentate binuclear structures, and ZrO₂ sites preferentially adsorbed As(III) and F in monodentate mononuclear configurations. This molecular structure obtained in the mono-adsorption system was integrated with the charge distribution multisite surface complexation model to accurately predict the As and F co-existing adsorption behaviors. The results in competitive adsorption, regeneration, and application evidenced that the {201}TiO₂-ZrO₂ composite is a promising adsorbent for simultaneous As and F removal.