PROTONATION OF PHOSPHATE ON THE SURFACE OF GOETHITE AS STUDIED BY CIR-FTIR AND ELECTROPHORETIC MOBILITY

CIR-FTIR spectroscopic studies have provided evidence for the formation of three different type of complexes, protonated and nonprotonated bridging bidentate as well as a nonprotonated monodentate, between orthophosphate ions and surface Fe(III) of a-FeOOH particles in aqueous suspensions. The speciation of these complexes is a function of pH and phosphate surface coverage (F). Furthermore, the combination of CIR-FTIR, adsorption isotherm, and electrophoretic mobility data allows us to calculate the intrinsic pK value (4.6) for the bridging bidentate iron phosphate surface complex. © 1990, American Chemical Society. All rights reserved.