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Oxidation of As III by Several Manganese Oxide Minerals in Absence and Presence of Goethite
Author(s) -
Xionghan FENG,
Wenfeng TAN,
Fan LIU,
RUAN Huada Daniel,
Jizheng HE
Publication year - 2006
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.2006.tb00238.x
Subject(s) - birnessite , goethite , chemistry , inorganic chemistry , manganese , oxide , cryptomelane , redox , adsorption , nuclear chemistry , manganese oxide , organic chemistry
Oxidation of As III by three types of manganese oxide minerals affected by goethite was investigated by chemical analysis, equilibrium redox, X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Three synthesized Mn oxide minerals of different types, birnessite, todorokite, and hausmannite, could actively oxidize As III to As V , and greatly varied in their oxidation ability. Layer structured birnessite exhibited the highest capacity of As III oxidation, followed by the tunnel structured todorokite. Lower oxide hausmannite possessed much low capacity of As III oxidation, and released more Mn 2+ than birnessite and todorokite during the oxidation. The maximum amount of As V produced during the oxidation of As III by Mn oxide minerals was in the order: birnessite (480.4 mmol/kg) > todorokite (279.6 mmol/kg) > hausmannite (117.9 mmol/kg). The oxidation capacity of the Mn oxide minerals was found to be relative to the composition, crystallinity, and surface properties. In the presence of goethite oxidation of As III by Mn oxide minerals increased, with maximum amounts of As V being 651.0 mmol/kg for birnessite, 332.3 mmol/kg for todorokite and 159.4 mmol/kg for hausmannite. Goethite promoted As III oxidation on the surface of Mn oxide minerals through adsorption of the As V produced, incurring the decrease of As V concentration in solutions. Thus, the combined effects of the oxidation (by Mn oxide minerals)—adsorption (by goethite) lead to rapid oxidation and immobilization of As in soils and sediments and alleviation of the As III toxicity in the environments.