This study explored the chemical properties of geomaterials in relation with their fluoride removal efficiencies from water under acidic conditions. Two types each of as-received and engineered steel slags were tested, and their F- removal efficiencies were compared with those of other common or commercially available acid spill response materials. The chemical properties of the geomaterials were analyzed by x-ray photoelectron spectroscopy to determine their surface elemental compositions and by Brunauer-Emmett-Teller analysis to determine their surface areas. The F- removal efficiencies were calculated based on the fluoride concentrations in the remaining solutions using an ion chromatography technique. A principal component analysis (PCA) was conducted to identify the dominant independent variables that influenced the F- removal efficiencies, revealing that the surface area was most closely correlated with the F- removal efficiency. A microscopic analysis of the geomaterials, conducted using an energy dispersion spectrometer technique after the F- sorption reaction had occurred revealed that the local Al, Si, or O concentration was an important latent independent variable for the F- removal efficiency. These variables had been hidden in the PCA results. Therefore, aluminosilicate-rich geomaterials with a high surface area offer primary candidates as effective sorbents for fluoride in water under acidic conditions. (C) 2017 Elsevier B.V. All rights reserved.