Unraveling Adsorption Mechanisms and Potential of Titanium Dioxide for Arsenic and Heavy Metal Removal from Water Sources

Arsenic and heavy metal contamination in water presents serious environmental and public health challenges, requiring effective treatment technologies. Titanium dioxide (TiO2) nanoparticles offer promising adsorption potential due to their high surface area, mesoporosity, and chemical stability. This study investigates the removal of As(V), Cd(II), Cu(II), and Pb(II) by TiO2 under environmentally relevant conditions (pH 3 and 7), commonly encountered in industrial and natural waters. TiO2 was characterized using SEM, XRD, FTIR, BET, and pHpzc analysis, confirming a mesoporous structure with mixed anatase/rutile phases. Adsorption followed Elovich kinetics, with the Langmuir model providing the best fit to the isotherm data. At pH 3, adsorption capacities (qm) were of the following order: Pb(II) 30.80 mg g−1 > Cd(II) 10.02 mg g−1 > As(V) 8.45 mg g−1 > Cu(II) 2.73 mg g−1; at pH 7, they were as follows: Cd(II) 26.75 mg g−1 > Pb(II) 26.20 mg g−1 > As(V) 8.50 mg g−1 > Cu(II) 5.05 mg g−1. These results highlight a pH-dependent mechanism involving both chemisorption and physisorption. Principal Component Analysis (PCA) revealed that physicochemical properties, particularly electronegativity, significantly influenced removal efficiency. TiO2 showed high, selective, and pH-responsive adsorption properties, supporting its use in sustainable water treatment. Future work should address nanoparticle recovery, regeneration, and performance under continuous flow conditions.