Removal of lead by TiO₂-modified activated carbon

Lead is a widespread contaminant in drinking water globally, primarily due to aging infrastructure and contaminated source water. Activated carbon (AC), although widely used due to its large specific surface area (SSA), exhibits limited affinity for Pb²⁺, particularly at environmentally relevant concentrations. Conversely, while titanium dioxide (TiO₂) demonstrates high adsorption affinity, its relatively high cost and tendency to aggregate limit its practical application. To overcome these limitations, we developed TiO₂-coated activated carbon (Ti-AC), which combines the stability and high SSA of AC with the strong binding capacity of amorphous TiO₂. Ti-AC was synthesized via a simple impregnation of AC with a TiOSO₄ solution, avoiding the complex procedures commonly employed for TiO₂-based materials. Comprehensive characterization using electron microscopy, X-ray diffraction, and BET analysis confirmed that amorphous TiO₂ was uniformly distributed without significantly reducing SSA. Batch adsorption tests showed Pb²⁺ removal efficiency notably increased from 30.4 % for unmodified AC to 63.4 % for 1 % Ti-modified AC. X-ray absorption near-edge structure (XANES) and FTIR analysis revealed that 1 % Ti adsorbed 48.5 % of the removed lead on the 1 %Ti-AC via OH complexation. In column filtration, Ti-AC consistently reduced effluent Pb²⁺ from 90 μg/L to below the U.S. EPA guideline of 10 μg/L for more than 40,000 bed volumes, whereas unmodified AC rapidly failed. These results demonstrate that Ti-AC offers a readily scalable, cost-effective strategy for lead removal, addressing the limitations of conventional AC and TiO₂ and advancing the development of reliable adsorbents for drinking water treatment.