An EXAFS study on the adsorption structure of phenyl-substituted organoarsenic compounds on ferrihydrite.

Adsorption structures of mono- and diphenyl substituted organoarsenic compounds (PAA and DPAA, respectively) on ferrihydrite were analyzed by extended X-ray absorption fine structure (EXAFS), which suggested that PAA and DPAA form inner-sphere complexes with ferrihydrite regardless of their bulky functional groups. In addition, coexistence of two types of inner-sphere complex modes, i.e. bidentate-binuclear and monodentate surface complexes was suggested by EXAFS fitting with two type of the As-Fe shell.