Removal of Mn(II) ions from aqueous neutral media by manganese‐oxidizing fungus in the presence of carbon fiber

Abstract

A manganese-oxidizing fungus was isolated from a hot spring in Japan. The fungus was increasingly effective at oxidizing Mn(II) ions as the concentration of organic carbon sources in the growth medium was decreased. The fungus oxidized 50 ppm of Mn(II) ions within 160 h in a pH 7.3 medium at 25jC. The presence of carbon fiber shortened the time to 80 h, and promoted steady oxidation. The oxidation products were identified by XPS and XRD to be poorly crystallized and amorphous MnO 2 , both with and without the fiber. These results suggest that the fiber participates in kinetically limited oxidation. The fungus was entangled with and clung to the fibers, and the oxidized Mn species accumulated on the fungus. Similarly shaped polyethylene telephthalate fiber did not enhance the oxidation, nor was adhesion of the fungus observed. Although the mechanism is still unknown, the present work shows that removal of Mn from solution through the precipitation and accumulation of Mn-oxides on the fungus in the presence of carbon fiber is a promising improvement for water treatment. B 2004 Wiley Periodicals, Inc.

Immobilization of Mn(II) Ions by a Mn-Oxidizing Fungus <I>Paraconiothyrium sp.-Like</I> Strain at Neutral pHs

“…The optimal pH of the strain is the lowest among those of the previously reported Mn-oxidizing fungi. [4][5][6] Out of the optimal pH range the standard deviation became large. Figure 2 shows the effect of peptone and yeast extract on Mn-removal by the strain at the initial pH 6.6.…”

“…The XRD pattern of the biogenic Mn deposit has a noisy background with an ambiguous, broad peak and two relatively sharp peaks, indicating that it is poorly crystalline, typical of most biogenic deposits. Two peaks at 12 and 37 in 2 are assigned to 002 of birnessite (Na 4 Mn(III) 6 Mn-(IV) 8 O 27 Á9H 2 O, JCPDS 23-1046), a broad peak near 2 ¼ 20 {25 can be tentatively assigned to 212 of birnessite. Although these assignments might not be definite, the biogenic Mn oxide contains birnnesite primarily, and the chemical forms of Mn in the biogenic Mn oxide is thought to be Mn(III) and/or Mn(IV) which were formed by the fungal Mn(II)-oxidation.…”

“…could be observed at initial Mn(II) ion concentrations up to a maximum of 125 gÁm À3 . 6) Besides, the maximum Mn-oxidizing rate for the strain KR21-2 of the Acremonium-like hyphomycete fungus revealed at 165 gÁm À3 of the initial Mn(II) ion concentration was reduced to nearly zero at 275 gÁm À3 . 5) On the contrary, the optimum condition for the Mn-oxidizing bacteria Leptothrix discophora was around 8 gÁm À3 of the initial Mn ion concentration, which is under the maximum contamination limit (MCL) for Mn in discharge water in Japan.…”

“…[1][2][3] In such places, pH is mostly in the range of 6-8 where Mn (II) ions are not capable to be chemically oxidized by oxygen. Several kinds of Mnoxidizing bacteria, such as Leptothrix, Arthrobactor, Bacillus, Pseudomonas, Micrococcus, 4) and a few kinds of Mnoxidizing fungi, 5,6) were isolated from fresh water, sea water, hydrothermal vents and sediments, and identified by morphological and genetic investigations.…”

Recent Developments in Microbiological Approaches for Securing Mine Wastes and for Recovering Metals from Mine Waters

“…Manganese is present in AMD predominantly as Mn 2+ , and although, like ferrous iron, it can be oxidized biologically to insoluble Mn 4+ , this reaction is thermodynamically unfavourable below pH ~4 and proceeds slowly (unless catalysed) below pH 10. Bacteria and fungi have been shown to promote manganese oxidation and precipitation at moderately acidic pH values (>5; [42,43]), which is far lower than the pH required (> pH 8-9) to secure effective manganese removal using active (lime-based) remediation.…”