Photodesorption of fulvic acid from iron oxide surfaces into aqueous solutions

Photodesorption of thin ®lms of fulvic acid adsorbed on planar iron oxide surfaces was monitored by ellipsometry. Desorption was ®rst observed at 546 nm, and additional fractions of the adsorbed acid left the surfaces at 405 and 365 nm. Similar kinetics for photodesorption was observed from metallic iron ®lms and from porous iron oxide prepared electrochemically by deposition on porous silicon substrates. Soluble photoproducts leaving the surface were monitored by UVabsorbance spectroscopy at 200 nm. Gaseous productswere not detected bymass spectrometry but the results seemed to indicate that not all of the photoproducts entered the liquid phase.Of the metal ®lms tested which adsorbed fulvic acid from aqueous solution (Fe,Cr, Ni,Al, and Pt), itwas only iron which exhibited a photodesorption effect.#2001 Elsevier Science B.V. All rights reserved.