Exploratory factor analysis of fluoride removal efficiency associated with the chemical properties of geomaterials

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.