Adsorption of phosphate and cadmium on iron (oxyhydr)oxides: A comparative study on ferrihydrite, goethite, and hematite

Iron (oxyhydr)oxides participate in a variety of geochemical processes, and hence control the cycling elements quality soils. The present work provides information about macroscopic adsorption behaviors microscopic mechanisms typical cations oxyanions (i.e., cadmium phosphate) on three omnipresent iron ferrihydrite (Fh), goethite (Gt), hematite (Hm)) single- double-solute systems, which can not only help understanding different (oxyhydr)oxides, but also be important developing robust accurate surface complexation models. In both Fh exhibited strongest capacity uptake phosphate cadmium, followed by Gt Hm; specifically, adsorbed amounts ions were ~ 6 times higher than those Hm. Phosphate synergistically minerals. situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra combining with two-dimensional correlation spectroscopic (2D-COS) analysis employed to unravel bonding modes single-solute although primary species Hm similar, i.e., protonated non-protonated bidentate complexes, more complexes found Gt; whereas diversified due complex nature surfaces, including monoprotonated bidentate, outer-sphere complexes. synergistic minerals analogous, electrostatic interaction, as well formation phosphate-bridged ternary precipitation; nevertheless, relative contributions distinct: attraction was predominant co-adsorption mechanism for Gt, while precipitation most significant among This study enlightening understand interaction between soil constituents, is crucial evaluate fate transport environmentally substances geological settings.