Spherical Fe–Mn/Silica Composite Adsorbent for Rapid and Trace-Level Arsenic Removal

Arsenic contamination in drinking water poses a serious global public health threat, driving an urgent need for cost-effective technologies capable of efficient trace-level arsenic removal. In this study, a spherical iron–manganese composite adsorbent (SMF) was fabricated by loading FeOOH onto MnO2-modified silica gel (S-MnO2) via an in situ precipitation method, aiming to achieve rapid and high-capacity removal of trace As(V). The material was systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and other techniques, and its adsorption performance was evaluated through batch experiments. The results demonstrated that SMF possesses a large specific surface area (346.08 m2/g) and a well-developed mesoporous structure, with Fe–Mn oxides uniformly dispersed on the silica support in an amorphous form. SMF exhibited ultrafast adsorption kinetics, achieving nearly complete As(V) removal from drinking water (>99%) within 10 min across a broad pH range (2–12) and effectively reducing residual arsenic to below the World Health Organization (WHO) guideline of 10 μg/L. The adsorption process followed the pseudo-second-order kinetic model, indicating a chemisorption-dominated monolayer adsorption mechanism. Furthermore, SMF demonstrated broad-spectrum removal capability toward other toxic metal(loid) ions, including As(III), Sb(III), Pb(II), Cd(II), Cu(II), Hg(II), Zn(II), Fe(III), and Mn(II). These findings establish SMF as a promising granular adsorbent for the advanced treatment of arsenic-contaminated drinking water and industrial wastewater.