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Hausmannite (Mn3O4) conversion to manganite (??-MnOOH) in dilute oxalate solution

Environmental Science and Technology

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Abstract

Oxalic acid retards the alteration of Mn3O4 to ??-MnOOH during aging at pH 7.4 ?? 0.2 in well-aerated, abiotic suspensions that contain 4.4 ?? 10-3 M total Mn. In solutions of 1.25 ?? 10-3 M oxalate and greater, about 15% of the initial Mn3O4 altered to ??-MnOOH by day 10, and in solutions of 6.7 ?? 10-4 M oxalate, about 45% altered to ??-MnOOH by day 67. Although precipitation continued through day 365, the degree of conversion remained the same as at day 10 and day 67, respectively. In oxalate-free suspensions, the conversion was about 80% complete by day 67 and 100% by day 109. Oxalate complexed most of the dissolved divalent Mn, lowered the free Mn(II) and MnSO40 concentrations, but increased the total dissolved Mn. Steric hindrance of surface reactions by a suggested manganese oxalate layer on the Mn3O4 surface may explain the blockage of the oxidation cycle.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Hausmannite (Mn3O4) conversion to manganite (??-MnOOH) in dilute oxalate solution
Series title:
Environmental Science and Technology
Volume
22
Issue:
1
Year Published:
1988
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
62
Last page:
70
Number of Pages:
9