title: Arsenic removal from acidic solutions with biogenic ferric precipitates.
abstract: Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment.
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland. Electronic address: sarita.ahoranta@tut.fi.
authors.forename: Sarita H
authors.initials: SH
authors.lastname: Ahoranta
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland. Electronic address: marika.kokko@tut.fi.
authors.forename: Marika E
authors.initials: ME
authors.lastname: Kokko
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland. Electronic address: stefano.papirio@unicas.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Papirio
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland; Department of Environmental Engineering, Yildiz Technical University, Davutpasa Campus 34220, Esenler, Istanbul, Turkey. Electronic address: bozkaya@yildiz.edu.tr.
authors.forename: Bestamin
authors.initials: B
authors.lastname: Özkaya
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland. Electronic address: jaakko.puhakka@tut.fi.
authors.forename: Jaakko A
authors.initials: JA
authors.lastname: Puhakka
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D019149:Bioreactors; D011232:Chemical Precipitation; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D012996:Solutions; D013431:Sulfates / Q000737:chemistry* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D012996:Solutions; D013431:Sulfates; D014874:Water Pollutants, Chemical; C492331:jarosite; D007501:Iron; D001151:Arsenic
keywords: Arsenic removal; Biogenic jarosite; Fluidized-bed reactor; Iron; pH control