Influence of sulfide concentration and macronutrients on the characteristics of metal precipitates relevant to metal recovery in bioreactors.
Purity and settling properties determine metal sulfide recovery from bioreactors. The influence of macronutrients commonly present in mineral media and wastewaters on Cu, Pb, Cd and Zn depletion kinetics and characteristics was evaluated in batch experiments with chemically produced sulfide at different concentrations. The metal depletion kinetics showed that metals with slower depletion rates (Zn and Cd) are susceptible to other removal mechanisms such as biosorption onto the sulfate reducing biofilm and precipitation with macronutrients when sulfide is below the stoichiometric metal to sulfide ratio. For Zn, the main mechanism of removal is its sorption onto apatite (Ca(5)(PO(4)))(3)(+)(OH(-)), a compound formed due to the presence of CaCl(2)·2H(2)O and KH(2)PO(4) in the mineral medium. All precipitates were 8.1-10.0μm regardless the sulfide concentration demonstrating that this parameter is less relevant for particle growth and settling, compared to the agglomeration of the precipitates.
Core Pollution Prevention and Control, UNESCO-IHE, Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands. d.villagomez@unesco-ihe.org
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Villa-Gomez
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Papirio
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van Hullebusch
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Farges
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Nikitenko
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Kramer
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Lens
D019149:Bioreactors; D007700:Kinetics; D008670:Metals / Q000737:chemistry* / Q000302:isolation & purification; D013054:Spectrophotometry, Atomic; D013440:Sulfides / Q000032:analysis*
D008670:Metals; D013440:Sulfides