Open AccessFerric oxyhydroxide microparticles in water
Author(s) -
Donald O. Whittemore,
Donald Langmuir
Publication year - 1974
Publication title -
environmental health perspectives
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 2.257
H-Index - 282
eISSN - 1552-9924
pISSN - 0091-6765
DOI - 10.1289/ehp.749173
Subject(s) - goethite , ferric , hydrous ferric oxides , chemistry , surface water , amorphous solid , environmental chemistry , specific surface area , mineralogy , inorganic chemistry , environmental engineering , adsorption , organic chemistry , environmental science , catalysis , sorption
Mineralogy and specific surface area are major controls on the stabilities of ferric oxyhydroxide microparticles in natural waters. The thermodynamic stabilities of ferric oxyhydroxides, as described by the activity product in solution pK = -log [Fe(3+)] [OH(-)](3) range from pK = 37.1 for freshly precipitated amorphous oxyhydroxide to pK = 44.2 for well crystallized goethite. The sizes of suspended oxyhydroxide particles in natural waters range from less than 0.01 mum to greater than 5 mum. Oxyhydroxides precipitated in the laboratory from solutions simulating high-iron natural waters are needlelike or lathlike in shape and have mean thicknesses as small as 60 A. Large specific surface areas resulting from the small sizes of ferric oxyhydroxide particles cause increased solubilities and thus decreased pK values. Specific surface areas of 40-170 m(2)/g determined for laboratory precipitates gave computed decreases in pK of 0.4 to 1.6 units.