Arsenate and Arsenite Adsorption and Desorption Behavior on Coprecipitated Aluminum:Iron Hydroxides

Although arsenic adsorption/desorption behavior on aluminum and iron (oxyhydr)oxides has been extensively studied, little is known about arsenic adsorption/desorption behavior by bimetal Al:Fe hydroxides. In this study, influence of the Al:Fe molar ratio, pH, and counterion (Ca2+ versus Na+) on arse...

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Bibliographic Details
Published in:Environmental science & technology 2007-02, Vol.41 (3), p.837-842
Main Authors: Masue, Yoko, Loeppert, Richard H, Kramer, Tim A
Format: Article
Language:English
Subjects:
Adsorption
Aluminum
Aluminum Hydroxide - chemistry
Applied sciences
Arsenates - chemistry
Arsenates - isolation & purification
Arsenic
Arsenites - chemistry
Arsenites - isolation & purification
Calcium - pharmacology
Chemical Precipitation
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Ferric Compounds - chemistry
Global environmental pollution
Hydrogen-Ion Concentration
Iron
Phosphates - chemistry
Pollution
Pollution, environment geology
Sodium - pharmacology
Water Pollutants, Chemical - isolation & purification
Water pollution
Water Purification - methods
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Summary:Although arsenic adsorption/desorption behavior on aluminum and iron (oxyhydr)oxides has been extensively studied, little is known about arsenic adsorption/desorption behavior by bimetal Al:Fe hydroxides. In this study, influence of the Al:Fe molar ratio, pH, and counterion (Ca2+ versus Na+) on arsenic adsorption/desorption by preformed coprecipitated Al:Fe hydroxides was investigated. Adsorbents were formed by initial hydrolysis of mixed Al3+/Fe3+ salts to form coprecipitated Al:Fe hydroxide products. At Al:Fe molar ratios ≤1:4, Al3+ was largely incorporated into the iron hydroxide structure to form a poorly crystalline bimetal hydroxide; however, at higher Al:Fe molar ratios, crystalline aluminum hydroxides (bayerite and gibbsite) were formed. Although approximately equal AsV adsorption maxima were observed for 0:1 and 1:4 Al:Fe hydroxides, the AsIII adsorption maximum was greater with the 0:1 Al:Fe hydroxide. AsV and AsIII adsorption decreased with further increases in Al:Fe molar ratio. AsV exhibited strong affinity to 0:1 and 1:4 Al:Fe hydroxides at pH 3−6. Adsorption decreased at pH > 6.5; however, the presence of Ca2+ compared to Na+ as the counterion enhanced AsV retention by both hydroxides. There was more AsV and especially AsIII desorption by phosphate with an increase in Al:Fe molar ratio.
ISSN:0013-936X
1520-5851
DOI:10.1021/es061160z