Selenium adsorption by goethite
The adsorption of Se by goethite was studied as a function of time (10- min-24 h), temperature (295.5 and 303.5 K), pH (4-11), particle concentration (3-300 mg/L), total Se concentration (0.02-5 x 10/sup -5/ M), oxidation states (Se(IV) and Se(VI)), and competing anion concentration ((anion)/(Se(IV) = 0.25 to 50,000) in order to assess the influence of these factors on Se mobility. The data indicate that (i) the surface sites of goethite are heterogeneous, (ii) the adsorption of selenite (Se(IV)) reaches equilibrium in 2 h and is completely reversible with respect to pH, (iii) the removal of selenite from solution increases with decreasing pH and increasing particle concentration, (iv) the adsorption edge for selenite shifts to lower pH values with increasing total selenite concentrations, (v) selenite adsorbs much more strongly than selenate (Se(VI)), and (vi) the influence of additional anions on selenite adsorption depends on the relative affinity of the anions for the surface and the relative concentrations of the anions. For a given anion concentration ratio, the competition sequence with selenite is phosphate > silicate greater than or equal to citrate > molybdate > bicarbonate/carbonate > oxalate > fluoride > sulfate. Therefore, the conditions that favor the mobility of Se in the environment with respect to adsorption are alkaline pH, high Se concentrations, oxidizing conditions, and high concentrations of additional anions that strongly adsorb.
- Research Organization:
- Geological Survey, Denver, CO (USA)
- OSTI ID:
- 6759693
- Report Number(s):
- CONF-871180-
- Journal Information:
- Soil Sci. Soc. Am. J.; (United States), Vol. 51:5; Conference: 51. annual meeting of the Soil Science Society of America, Atlanta, GA, USA, 29 Nov 1987
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GOETHITE
SORPTIVE PROPERTIES
SELENIUM
ADSORPTION
ENVIRONMENTAL TRANSPORT
ANIONS
PH VALUE
CHARGED PARTICLES
ELEMENTS
IONS
MASS TRANSFER
MINERALS
OXIDE MINERALS
SEMIMETALS
SORPTION
SURFACE PROPERTIES
510200* - Environment
Terrestrial- Chemicals Monitoring & Transport- (-1989)