US EPA

1514501 

Journal Article 

Chromium(III) oxidation by delta-manganese oxide: 1. Characterization 

Fendorf, SE; Zasoski, RJ 

1992 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

26 

1 

79-85 

English 

10.1021/es00025a006 

WOS:A1992GY59000014 

BIOSIS COPYRIGHT: BIOL ABS. The oxidation of Cr(III) by a common naturally occurring form of manganese oxide, delta-MnO2, was characterized over a range of Cr(III) concentrations and pH values. Cr(III) oxidation was limited as pH and Cr(III) concentrations increased. Reaction products, Mn(II) and Cr(VI), did not limit Cr(III) oxidation. Initial Cr(III) oxidation rates were very rapid at pH = 5, but were subsequently followed by a dramatic rate decline. Thermodynamic calculations using solution species indicated the reactio Cr(III) at pH > 3.5 appears to prohibit the extent of oxidation. Various mechanisms may account for the electrophoretic mobility and oxidation reactions; however, surface precipitation of chromium hydroxide seems to be the most plausible explanation based on our results. Chromium oxidation was dependent on Cr(III) concentration, pH, initial surface area, and ionic strength. 

MINERALS/ANALYSIS; MINERALS; ENVIRONMENTAL POLLUTANTS/POISONING; OCCUPATIONAL DISEASES; AIR POLLUTION; SOIL POLLUTANTS; WATER POLLUTION; Biochemical Methods-Minerals; Biochemical Studies-Minerals; Toxicology-Environmental and Industrial Toxicology; Public Health: Environmental Health-Air; Soil Science-Physics and Chemistry (1970- ); 18540-29-9; 16065-83-1