title: Interaction of inorganic arsenic with biogenic manganese oxide produced by a Mn-oxidizing fungus, strain KR21-2.
abstract: In batch culture experiments we examined oxidation of As(III) and adsorption of As(III/V) by biogenic manganese oxide formed by a manganese oxide-depositing fungus, strain KR21-2. We expected to gain insight into the applicability of Mn-depositing microorganisms for biological treatment of As-contaminated waters. In cultures containing Mn2+ and As(V), the solid Mn phase was rich in bound Mn2+ (molar ratio, approximately 30%) and showed a transiently high accumulation of As(V) during the early stage of manganese oxide formation. As manganese oxide formation progressed, a large proportion of adsorbed As(V) was subsequently released. The high proportion of bound Mn2+ may suppress a charge repulsion between As(V) and the manganese oxide surface, which has structural negative charges, promoting complex formation. In cultures containing Mn2+ and As(III), As(III) started to be oxidized to As(V) after manganese oxide formation was mostly completed. In suspensions of the biogenic manganese oxides with dissolved Mn2+, As(III) oxidation rates decreased with increasing dissolved Mn2+. These results indicate that biogenic manganese oxide with a high proportion of bound Mn2+ oxidizes As(III) less effectively than with a low proportion of bound Mn2+. Coexisting Zn2+, Ni2+, and Co2+ also showed similar effects to different extents. The present study demonstrates characteristic features of oxidation and adsorption of As by biogenic manganese oxides and suggests possibilities of developing a microbial treatment system for water contaminated with As that is suited to the actual situation of contamination.
authors.affiliation: Institute for Environmental Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. taniy@sea.u-shizuoka-ken.ac.jp
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Tani
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Miyata
authors.forename: Maiko
authors.initials: M
authors.lastname: Ohashi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ohnuki
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Seyama
authors.forename: Keisuke
authors.initials: K
authors.lastname: Iwahori
authors.forename: Mitsuyuki
authors.initials: M
authors.lastname: Soma
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D001673:Biodegradation, Environmental; D005658:Fungi / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D014873:Water Pollutants / Q000302:isolation & purification*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D014873:Water Pollutants; C027424:manganese oxide; D001151:Arsenic