Rapid and synergistic adsorption of arsenic and fluoride by bifunctional Al/Ce oxides in complex geothermal matrices

A porous aluminum–cerium (Al/Ce) composite oxide was innovatively synthesized via a one-step, template-free evaporation–pyrolysis route, enabling in-situ formation of sulfate-templated mesopores and dual-functional –OH/SO 4 2 ⁻ sites. Designed to address the severe ion interference of geothermal water, this bifunctional adsorbent achieved rapid, simultaneous removal of arsenic (As) and fluoride (F⁻) with high efficiencies (93.8 % As, 91.5 % F⁻) within 15 min. Maximum adsorption capacities reached 251 mg/g (As) and 297 mg/g (F⁻), following pseudo-second-order kinetics and Freundlich isotherms. Thermodynamic analysis confirmed spontaneous, endothermic chemisorption. Structural characterizations (FT-IR, XRD, XPS) revealed ion exchange and surface complexation mechanisms via formation of Al–F, Ce–F, and Ce–O–As bonds. Remarkably, in real geothermal matrices rich in competing ions, removal efficiencies exceeded 96 %, underscoring the composite's strong anti-interference performance. This study demonstrates a scalable, environmentally friendly strategy for fabricating robust, synergistic adsorbents tailored for complex wastewater treatment.