The interaction of Prussian blue and dissolved hexacyanoferrate ions with goethite (alpha-FeOOH) studied to assess the chemical stability and physical mobility of Prussian blue in soils

Colloidal Prussian blue and dissolved hexacyanoferrate ions strongly intera ct with the surface of goethite (alpha -FeOOH) particles. Whereas Prussian blue is deposited on the surface of goethite as a solid phase with all the properties typical of solid Prussian blue, the hexacyanoferrate ions form i nitially a layer of surface bound hexacyanoferrate ions, which exhibit prop erties intermediate between those of free hexacyanoferrate ions and hexacya noferrate ions bound in Prussian blue. The products of interaction of goeth ite with Prussian blue and hexacyanoferrate ions were studied by voltammetr y of immobilized microcrystals. infrared spectrometry, Vis diffuse reflecti on spectrometry, transmission electron microscopy, and ESR spectroscopy. Th e kinetics of Prussian blue destruction was measured by solution Vis spectr ometry and also by voltammetry of solid microcrystals, The remarkable stabi lity of Prussian blue in soils ran be explained by its strong adherence as a solid phase to iron oxides and oxide hydroxides in soils, This prevents t he formation of soluble colloids of Prussian blue. It does not prevent the hydrolysis of Prussian blue to iron oxide hydroxides and hexacyanoferrate(I I) ions at elevated pH which proceeds at almost the same rate as that of pu re Prussian blue colloid. Even when this hydrolysis of Prussian blue occurs , it is the hexacyanoferrate(II) that is effectively adsorbed on the surfac e of iron oxide hydroxides, again decreasing the physical mobility of hexac yanoferrate, (C) 2001 Academic Press.