Removal of trivalent and hexavalent chromium by seaweed biosorbent

Journal Article · Tue Sep 15 04:00:00 EDT 1998 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es971073u· OSTI ID:655441

Kratochvil, D; Volesky, B ^[1]; Pimentel, P ^[2]

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1. McGill Univ., Montreal (Canada). Dept. of Chemical Engineering
2. CETEC, Belo Horizonte, Minas Gerais (Brazil)

Protonated or Ca-form Sargassum seaweed biomass bound up to 40 mg/g of Cr(III) by ion exchange at pH 4. An ion-exchange model assuming that the only species taken up by the biomass was Cr(OH){sup 2+} successfully fitted the experimental biosorption data for Cr(III). The maximum uptake of Cr(VI) by protonated Sargassum biomass at pH 2 was explained by simultaneous anion exchange and Cr(VI) to Cr(III) reduction. At pH <2.0, the reduction of Cr(VI) to Cr(III) dominated the equilibrium behavior of the batch systems, which was explained by the dependence of the reduction potential of HCrO{sub 4}{sup {minus}} ions on the pH. At pH >2.0, the removal of Cr(VI) was linked to the depletion of protons in equilibrium batch systems via an anion-exchange reaction. The optimum pH for Cr(VI) removal by sorption lies in the region where the two mechanisms overlap, which for Sargassum biomass is in the vicinity of pH 2. The existence of the optimum pH for the removal of Cr(VI) may be explained by taking into account (a) the desorption of Cr(III) from biomass at low pH and (b) the effect of pH on the reduction potential of Cr(VI) in aqueous solutions. Seventy percent of Cr(VI) bound to the seaweed at pH 2 can be desorbed with 0.2 M H{sub 2}SO{sub 4} via reduction to Cr(III).

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-91ER45439; FG06-90ER45425
• OSTI ID: 655441
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 18 Vol. 32; ISSN 0013-936X; ISSN ESTHAG
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CHROMIUM
ION EXCHANGE
MATHEMATICAL MODELS
SEAWEEDS
SORPTION
WASTE PROCESSING
WASTE WATER